The Science of the Total Environment, 99 (1990) 67-76 Elsevier Science Publishers B.V., Amsterdam
67
MATERNAL PLASMA CONCENTRATIONS OF MAGNESIUM, CALCIUM, ZINC AND COPPER IN NORMAL AND PATHOLOGICAL PREGNANCIES
P. BORELLA1'*, A. SZILAGYI2, G. THAN2, I. CSABA2, A. GIARDINO1 and F. FACCHINETTI~ llstituto di Igiene, Universita' degli Studi di Modena, Via Carnpi 287, 1-41100 Modena (Italy) 2Pecs Medical School, Department of Obstetrics and Gynecology, H-7643 Pecs (Hungary) 3Istituto di Ostetricia e Ginecologia, Universita" degli Studi di Modena, Via del Pozzo, 1-41100 Modena (Italy)
(Received October 12th, 1989; accepted January 17th, 1990)
ABSTRACT In this study, plasma levels of magnesium, calcium, zinc and copper were simultaneously determined in pregnancies complicated by either abortion, intrauterine growth retardation (IUGR), diabetes or EPH (edema, proteinuria, hypertension) gestosis. The levels of the four cations in non-pregnant women and in healthy, pregnant women were also determined. Compared with controls, a significant decrease in magnesium, with increase of the Ca/Mg ratio, was found in spontaneous abortions, but not when patients had a successful continuation of pregnancy. In EPH gestosis, total calcium was reduced, with a significant decrease of the plasma Ca/Mg ratio. A slight, but significant, increase in plasma zinc was observed in women affected by either diabetes or IUGR, probably as a result of reduced zinc uptake by the fetus. In addition, higher copper levels were found in the pathologies studied, with the exception of missed abortions. The possible role of an altered Ca/Mg ratio homeostasis in relation to gestational pathologies is discussed.
INTRODUCTION It has been r e c o g n i z e d t h a t c h a n g e s in m i n e r a l m e t a b o l i s m could h a v e a h a r m f u l effect on fetal g r o w t h (Pitkin, 1985; Adeniyi, 1987; S w a n s o n a n d King, 1987). The r e c e n t l i t e r a t u r e indicates t h a t a l t e r a t i o n s in p l a s m a a n d cellular zinc are a s s o c i a t e d with v a r i o u s obstetric p a t h o l o g i e s (Tuttle et al., 1985; Wibell et al., 1985; Wells et al., 1987; L a z e b n i k et al., 1988). I n addition, plasma m a g n e s i u m was f o u n d to decrease d u r i n g a b n o r m a l g e s t a t i o n (Wibell et al., 1985; M i m o u n i et al., 1987; Ajayi, 1988), and the effect of m a g n e s i u m supplem e n t a t i o n on the o u t c o m e of p r e g n a n c y has been e x a m i n e d ( T h u r n a u et al., 1987; R a m a n a t h a n et al., 1988; S p a t l i n g a n d Spatling, 1988). A b n o r m a l i t i e s in c a l c i u m r e g u l a t i o n h a v e been r e p o r t e d in b o t h diabetes (Godeny et al., 1986; Belizan et al., 1988; Roelofsen et al., 1988) a n d pre-eclampsia (Taufield et al., 1987); c h a n g e s in p l a s m a copper h a v e also been observed (HeijkenskjSld and *Author to whom requests for reprints should be addressed.
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© 1990- - Elsevier Science Publishers B.V.
68
Hedenstedt, 1962; O'Leary et al., 1965; Bodgen et al., 1978; Metcoff et al., 1981; Kiilholma et al., 1984). Data on cation patterns in pregnancy are conflicting; in only a few cases was more than one cation determined, thus a sufficiently adequate description of the mineral levels in different complications in human pregnancy is lacking. In this study, we simultaneously determined zinc, copper, magnesium and calcium in plasma of pregnant women in relation to either abortion, diabetes, gestosis or intrauterine growth retardation (IUGR), in order to clarify the association between altered mineral levels and pregnancy disorders of the first and third trimester. The results are compared with those obtained for controls with uncomplicated pregnancies. In addition, the levels of the four cations in non-pregnant women were determined, in order to compare them with those found in healthy, pregnant women. MATERIALSAND METHODS In total, 84 hospitalized, pregnant women suffering from complications were recruited. Twenty-four patients were studied at first trimester (6--16 weeks of gestation) with threatened abortion: 12 underwent interruption of pregnancy. In these cases, blood samples were taken after ultrasound scan and urinary hCG tests, 1 2 days before dilatation and curettage. For the remaining patients, pregnancies continued, and embryo well-being was monitored with ultrasound scan and urinary hCG excretion for at least 1 month to rule out missed abortion. Sixty patients were studied at the third trimester (between 29 and 40 weeks of gestation). They suffered from diabetes (n = 18), intrauterine growth retardation (n = 18) and EPH (edema, proteinuria, hypertension) gestosis (n = 24). Diabetic patients were mainly insulin-dependent diabetics, with the exception of three patients with gestational diabetes. They were on a diet, or on prophylactic insulin treatment, and morning glucose levels were constantly maintained between 4 and 6mmoll 1. In these cases, blood samples were collected in the morning, 1.5h after insulin injection. Birth weights ranged between 2340 and 4210 g. Diagnosis of IUGR was made with the help of ultrasound scan and biochemical monitoring (hPL and pregnancy specific Bl-glycoprotein SP1) performed in the 34th and 37th week. Termination of pregnancy occurred between 38 and 42 weeks in all cases, with the exception of three patients who delivered in the 35th, 36th and 37th week of gestation. Caesarian section was necessary in three cases and forceps were used in two cases. The therapy was 02 inhalation (81 min-1) and amino acids infusion. Birth weights ranged between 1930 and 2730 g, and were below the 10th centile. For patients with EPH gestosis, edema was present in all but two cases; proteinuria (> 300mg of urinary proteins per 24h) was found in 14 of 24 patients; and hypertension was present in all but three cases. Hypertension in
69 pregnancy was defined as the presence of a blood pressure of at least 140/ 90mm Hg or a rise of 30 mm Hg in systolic pressure or 15 mm Hg in diastolic pressure. Patients were treated with fl-blockers and K-sparing diuretics. Deliveries occurred at term in all but six cases, and birth weights were between 1100 and 3930g: five were under the 10th centile, and four were between the 10th and the 25th centile. The control group consisted of 100 healthy, pregnant women: 41 at first trimester, 24 at second and 35 at third. None of them suffered from any pregnancy complication in either the prenatal or the perinatal period. Age, pre-pregnancy weight, weight gain and parity were similar between controls and patients. In addition, a group of 21 non-pregnant women aged 24-37 years were examined for the same cations, in order to define non-pregnant levels. Blood was collected from each participant in the fasting state, and plasma was obtained after centrifuging heparinized blood at 1200g for 10 min at 4°C. Particular attention was paid to avoid blood haemolysis and metal contamination during blood collection by using stainless steel needles and plastic syringes. Disposable plastic test-tubes were used whenever possible and all glassware was soaked in dilute hydrochloric acid solution for at least 16 h, then rinsed with demineralized, double-distilled water. No metal release was observed from tubes or materials. Zinc and copper were determined by flame atomic absorption spectrophotometry (AAS) following the procedure of Smith et al. (1979). The method of standard additions was used to check plasma results, as previously described (Vivoli et al., 1987). For magnesium and caleium analyses, plasma was diluted with 0.1% lanthanum chloride solution. Appropriate magnesium and calcium standards were prepared in the same diluent solution. Accuracy was determined by adding 0.5-2.0mmolMgl 1 and 2.(~4.0mmolCal-1. The recovery ranged from 98.2 to 101.2% for both cations. The precision, calculated on 10 replicates, was high (< 2%). A Perkin-Elmer AAS Model 5000 equipped with an air-acetylene flame was used for all determinations, making instrument adjustments according to the manufacturer's instruction manual. Statistical analyses were carried out using Student's t test and linear correlation coefficients. All cations were normally distributed, thus non-log transformation of data was performed before statistical treatment. RESULTS Plasma levels of the four cations in normal pregnancies, and in non-pregnant women, are shown in Fig. 1. A progressive decrease in plasma zinc was observed throughout pregnancy, whereas the reverse was found for copper. Magnesium and calcium reached their lowest level during the second trimester, with a slight, but insignificant, increase in the third trimester. When patients suffering from threatened abortion or spontaneous abortion
70 HEALTHY PREGNANT WOMEN ,:3.0
b
[~]
2.5
non-pregnant
[]first []second I
2.0
trim. tr~m.
third trim.
4. E 1.o
.5
o Calcium
5"0'
m Magnesium
a
45
apc
4.0 ¸ 35 ¸ ,~0 ¸
< 25 ¸ 20 ¸ 15 ¸ 10 5 0 Copper
Zinc
Fig. 1. P l a s m a c o n c e n t r a t i o n s of t h e four c a t i o n s in n o n - p r e g n a n t and healthy, p r e g n a n t women. (a) p < 0.001, (b) p < 0.05 compared with n o n - p r e g n a n t women, (c) p < 0.01 b e t w e e n first and second trimester, (d) p < 0.01 b e t w e e n second and t h i r d trimester. TABLE 1
P l a s m a magnesium, calcium, zinc and copper c o n c e n t r a t i o n s (mean _+ SD) of p a t i e n t s suffering from abortion or t h r e a t e n e d abortion First t r i m e s t e r Controls (n = 41) M a g n e s i u m (mmol1-1) Calcium (mmoll -~) Zinc ~ m o l l
i)
Copper ~ m o l 1 - 1 ) *p < 0.02; ***p < 0.001.
0.80 + 0.11
Abortion (n = 12) 0.67 + 0.13"**
T h r e a t e n e d abortion (n = 12) 0.75 _+ 0.07
2.43 _+ 0.32
2.38 + 0.26
13.13 _+ 2.37
13.64 _+ 2.35
11.31 _+ 2.11"
2.30 +
0.32
26.05 _+ 6.53
28.22 + 4.68
46.53 +_ 13.18"
71 w e r e c o n s i d e r e d (Table 1), p l a s m a m a g n e s i d m w a s significantly r e d u c e d in women undergoing pregnancy termination when compared with healthy c o n t r o l s of s i m i l a r g e s t a t i o n a l period (p < 0.001). P a t i e n t s h a v i n g a successful c o n t i n u a t i o n of p r e g n a n c y s h o w e d l o w e r levels of zinc a n d h i g h e r levels of c o p p e r w i t h r e s p e c t to c o n t r o l s a n d to p a t i e n t s w i t h a b o r t i o n . T h e p l a s m a levels of the f o u r c a t i o n s in t h i r d t r i m e s t e r p a t i e n t s are g i v e n in T a b l e 2, a n d are c o m p a r e d w i t h c o n t r o l s at a s i m i l a r g e s t a t i o n a l period. P l a s m a c a l c i u m w a s s i g n i f i c a n t l y r e d u c e d in e c l a m p t i c patients, w h e r e a s o n l y a slight d e c r e a s e of this c a t i o n was o b s e r v e d in p a t i e n t s w i t h I U G R . T h e zinc conc e n t r a t i o n for p a t i e n t s w i t h d i a b e t e s or I U G R w a s s i m i l a r to t h a t for c o n t r o l s a t second t r i m e s t e r (11.32 + 2 . 3 0 # m o l l 1), a n d s i g n i f i c a n t l y h i g h e r t h a n t h a t f o u n d at t h i r d t r i m e s t e r . S i g n i f i c a n t i n c r e a s e s of c o p p e r w e r e o b s e r v e d in all g r o u p s of p a t i e n t s . T h e r e s u l t s did not c h a n g e w h e n e c l a m p t i c p a t i e n t s w h o delivered a g r o w t h r e t a r d e d n e o n a t e (n = 5) w e r e included in the I U G R group. No v a r i a t i o n in m e a n p l a s m a m a g n e s i u m b e t w e e n g r o u p s w a s observed. H o w e v e r , w h e n p a t i e n t s w e r e subdivided a c c o r d i n g to l u n a r m o n t h (29-32 weeks, 33-36 weeks, 37-41 weeks), a slight, b u t significant, r e d u c t i o n of m a g n e s i u m was o b s e r v e d for b o t h d i a b e t e s (0.68 + 0.07 m m o l 1-1) a n d I U G R (0.69 + 0 . 1 0 m m o l l - 1 ) , b o t h e x a m i n e d at 29-32 w e e k s w i t h r e s p e c t to c o n t r o l s (0.78 _+ 0 . 0 9 m m o l l - l , p < 0.05). T h e m o l a r C a / M g r a t i o w a s c a l c u l a t e d , a n d it was f o u n d to be fairly c o n s t a n t in n o n - p r e g n a n t w o m e n (3.14 _+ 0.21) and t h r o u g h o u t p r e g n a n c y : 3.07 + 0.33 at first t r i m e s t e r , 3.21 _+ 0.36 at t h e second, 3.19 + 0.24 at the third. T h e m o l a r C a / M g r a t i o s a r e i l l u s t r a t e d in Fig. 2. A significant i n c r e a s e is o b s e r v e d w i t h a b o r t i o n s , w h e r e a s in p a t i e n t s w i t h E P H gestosis the C a / M g r a t i o was l o w e r t h a n in c o n t r o l s (2.86 vs 3.19, p < 0.05). TABLE 2 Mean plasma content (mean + SD) of the examined cations in women with diabetes, growth retardation and pre-eclampsia/toxemia Third trimester Magnesium (mM1-I)
Calcium (raM1-1)
Controls (n = 35)
0.75 _+ 0.07
2.39 _+ 0.23
Diabetes (n = 18)
9.76 + 0.n/
2.40 _+ 0.28
11.73 _+ 1.80"**
51.95 + 7.45***
Growth retardatiol (n = 16)
0.76 _+ 0.14
2.26 _+ 0.30
11.70 + 1.83"**
54.56 _+ 8.79***
Pre-eclampsia/ toxemia (n = 24)
0.77 _+ 0.11
2.15 + 0.26***
10.49 + 2.28
51.78 + 19.16"*
**p < 0.01; ***p < 0.001.
Zinc (uM1-1) 9.60 + 2.29
Copper (,uM1-I) 40.34 _+ 8.85
72 Ca/Mg Ratio
F-
Control=
]
Abo~on T h r e o t e n e d Abort,
Control~ D|obetes IUGR EPH-Gestosis
]
*
0 .:,:o '2:o '3:o ',:o '5:0 Fig. 2. Plasma Ca/Mg molar ratio in patients and controls; *p < 0.01.
When the molar Cu/Zn ratios were calculated, we found no difference between patients and controls, with the exception of subjects suffering from threatened abortion. In those cases, the molar Cu/Zn ratio was 4.41 compared with 2.07 for controls (t = 4.73, p < 0.001). Correlation coefficients were determined between the measured parameters, and we found a high positive correlation between magnesium and calcium in the control group at both first and last trimester (r = 0.71,p < 0.001), whereas there was no such correlation for the patients. No other correlations were found between the cations examined, nor between cations and birth weights. DISCUSSION
We have determined plasma concentrations of zinc, copper, calcium and magnesium, modifications of which have been implicated in the interference of normal pregnancy development. The trends of the four cations in normal pregnancies are in agreement with other findings (Olatunbosun et al., 1975; Kundu et al., 1985; Sheldon et al., 1985; Ajayi, 1988), and the range of values is comparable to those in the literature (Schenker et al., 1969; Hambidge and Droegemueller, 1974; Meadows et al., 1981; Campbell-Brown et al., 1985; Pitkin, 1985). The measurements were carried out for four different pathological conditions, and the most interesting findings are: (i) A decrease in plasma magnesium, with a concomitant increase in the Ca/Mg ratio, with abortions; (ii) A decrease in plasma calcium and the Ca/Mg ratio in patients with EPH gestosis; (iii) An increase in plasma copper and zinc in subjects suffering from diabetes or IUGR.
73 Compared with controls, lower mean plasma magnesium levels (17% lower) were found in patients experiencing an abortion, but not when the abortion was only threatened, and the pregnancy successfully continued. In recent experimental studies, magnesium deficiency has been shown to increase significantly both fetal loss rate and teratogenicity (Hurley et al., 1976), and the threshold maternal serum magnesium level for embryotoxic effect was found to be ~ 24% below the control value (Gfinther et al., 1981). Indeed, in the present study, five of 12 women undergoing a first trimester abortion had a plasma magnesium level 24% below the mean value of the control group. Furthermore, a high incidence of abortion in diabetics with low serum magnesium has been reported (Mimouni et al., 1987). Thus a causal relationship between magnesium deficiency and spontaneous abortion deserves to be evaluated further. On the other hand, we could not find any difference in magnesium levels when patients with EPH gestosis and IUGR were examined, in agreement with other studies (Boston et al., 1989). Although magnesium therapy has been associated with a reduction in maternal and fetal morbidity, it was not effective against pre-eclampsia or fetal growth retardation (Spatling and Spatling, 1988). On the contrary, preliminary findings on amniotic fluid levels seem to associate IUGR with increased fetal magnesium excretion (Facchinetti et al., 1989). In patients suffering from EPH gestosis, there was a reduction in plasma calcium, thus supporting the hypothesis of an association between calcium metabolism and pregnancy-induced hypertension (Taufield et al., 1987; Belizan et al., 1988). The mechanism involved is unknown, although it was hypothesized that both reduced parathyroid hormone secretion and increased calcium excretion through the urinary system could play a role (Belizan et al, 1983). According to epidemiological data, the incidence of eclampsia was found to vary inversely with calcium intake (Villar et al., 1983), and both oral calcium and magnesium supplementation have been reported to decrease the incidence of pre-eclampsia and to lower blood pressure (Belizan et al., 1983). Despite the existence of significant changes in both magnesium and calcium levels during pregnancy, their molar ratio was fairly constant both in non-pregnant women and throughout pregnancy. Furthermore, the relationship between calcium and magnesium observed in healthy pregnancies disappeared in pathological groups, as reported for other pathological conditions (Turkington and Naji, 1985; Chueca et al., 1987). Our results suggest that, in addition to the absolute concentrations of the two cations, their ratio and the relationships between the two metals might be of particular interest as indices of abnormal gestation. A high Ca/Mg ratio has been experimentally shown to provoke vasospasm in certain blood vessels in vitro, and it has been suggested that this is responsible for the spasm of umbilical and placental vasculature in normal women at the end of pregnancy (Altura et al., 1983). In our study, a higher than normal Ca/Mg ratio in plasma was found with abortions, whereas the ratio was reduced in patients with EPH gestosis. The limited number of women examined does not allow any definitive conclusion, but the role of
74 Ca/Mg homeostasis during obstetric pathologies requires further consideration. The finding of higher levels of zinc in patients carrying a growth-retarded fetus is in agreement with other studies (Cherry et al., 1981; Metcoff et al., 1981), although the opposite trend has also been observed (Jameson, 1976). The decrease in plasma zinc after 14 weeks gestation could be considered physiological, being secondary to plasma volume expansion, which is in turn related to birth weight (Hytten and Leitch, 1971; Tuttle et al., 1985). Indeed, a reduced plasma volume response to pregnancy has been observed in a number of women who delivered growth-retarded babies (Tuttle et al., 1985). Unfortunately, we could not measure plasma volume, and a clear correlation with birth weight was not determined. More than one factor, and particularly a higher fetal uptake of zinc, might be involved in the trend of this cation during the third trimester. It is worth noting that the values we found in diabetes and growth retardation at third trimester are similar to those found in the second trimester of the control pregnancies. Thus, in abnormal gestations, both reduced plasma expansion and/or reduced transfer of this cation to the fetus might be the reason for the higher zinc levels in maternal plasma at third trimester. In studies of diabetics, non-pregnant, insulin-dependent diabetics and those in early pregnancy had lower levels of zinc and magnesium than controls. For zinc, there was no difference at delivery, whereas a difference in serum magnesium persisted during pregnancy (Wibell et al., 1985). In our study group, a slight reduction in magnesium was found only during the seventh month of gestation. This finding agrees with the conclusion that, for well-regulated diabetic women, the relatively small deviation of magnesium from control levels should not be over-estimated. A high plasma copper concentration seems to be a common feature in women suffering from either pre-eclampsia, or diabetes and threatened abortion, confirming the observations of other authors (Heijkenskjold and Hedenstedt, 1962; Schenker et al., 1969; F a t t a h et al., 1976; Godeny et al., 1986), although the opposite trend has also been reported (Hiilholma et al., 1984). It has been suggested that high serum copper could be found in women with hyperactive placentas and lower values in women having placental insufficiency (Prema, 1980), although our data are inconsistent with such a hypothesis. To clarify our findings, the relationship between copper and hormonal trends, including insulin levels, requires further evaluation, taking into account the possible interfering effect of therapy on copper. REFERENCES Adeniyi, F.A.A., 1987. The implications of hypozincemiain pregnancy. Acta Obstet. Gynecol. Scand., 66: 579-587. Ajayi, G., 1988. Serum magnesiumconcentration in premenopausal, menopausal women, during normal and EPH-gestosis pregnancy and the effect of diuretic therapy in EPH-gestosis. Magnesium Bull., 10:72 76.
75 Altura, B.M., B.T. Altura and A. Carella, 1983. Magnesium deficiency-induced spasms of umbilical vessels: relation to preeclampsia, hypertension, growth retardation. Science, 221: 376-377. Belizan, J.M., J. Villar, A. Zalazar, L. Rojas, D. Chan and G.F. Bryce, 1983. Preliminary evidence of the effect of calcium supplementation on blood pressure in normal pregnant women. Am. J. Obstet. Gynecol., 146: 175-180. Belizan, J.M., J. Villar and J. Repke, 1988. The relationship between calcium intake and pregnancy-induced hypertension: up-to-date evidence. Am. J. Obstet. Gynecol., 158: 898-902. Bodgen, J.D., I.S. Thind, B. Lauria and H. Caterini, 1978. Maternal and cord blood metal concentrations and low birth weight - a case control study. Am. J. Clin. Nutr., 31: 1181-1187. Boston, J.L., R.E. Beauchene and D.P. Cruikshank, 1989. Erythrocyte and plasma magnesium during teenage pregnancy: Relationship with blood pressure and pregnancy-induced hypertension. Obstet. Gynecol., 73: 169~174. Campbell-Brown, M., R.J. Ward, A.P. Haines, W.R.S. North, R. Abraham and I.R. McFadyen, 1985. Zinc and copper in Asian pregnancies - is there evidence for a nutritional deficiency? Br. J. Obstet. Gynaecol., 92: 875-885. Cherry, F.F., E.A. Bennett, G.S. Bazzano, L.K. Johnson, G.J. Fosmire and H.K. Batson, 1981. Plasma zinc in hypertension/toxemia and other reproductive variables in adolescent pregnancy. Am. J. Clin. Nutr., 34:2367-2375. Chueca, P., S. Serrano, M.E. Carrasco and C. Chueca, 1987. Correlation between calcium and magnesium in plasma or serum? Clin. Chem., 33: 304-305. Facchinetti, F., P. Borella, M. Valentini, A. Segre, C. Battaglia and A.R. Genazzani, 1989. Intrauterine growth retardation is associated with increased levels of magnesium in amniotic fluid. Eur. J. Obstet., Gynecol. Reprod. Biol., 32:227 232. Fattah, M.M., F.K. Ibrahim, M.A. Ramada and M.B. Sammour, 1976. Ceruloplasmin and copper level in maternal and cord blood and in the placenta in normal pregnancy and in pre-eclampsia. Acta Obstet. Gynecol. Scand., 55:383 385. Godeny, J., J. Borbely-Kiss, E. Koltay, S. Laszlo and G. Szabo, 1986. Determination of trace and bulk elements in plasma and erythrocytes of diabetic pregnant women by Pixe method. Int. J. Gynaecol. Obstet., 24:201 207. Gfinther, T., H. Ising, F. Mohr-Nawroth H, I. Chahoud and H.J. Merker, 1981. Embryotoxic effects of magnesium deficiency and stress on rats and mice. Teratology, 24: 225-233. Hambidge, K.M. and W. Droegemueller, 1974. Changes in plasma and hair concentrations of zinc, copper, chromium, and manganese during pregnancy. Obstet. Gynecol., 44: 666~72. HeijkenskjSld, F. and S. Hedenstedt, 1962. Serum copper determinations in normal pregnancy and abortion. Acta Obstet. Gynecol. Scand., 41:41 47. Hurley, I.S., C. Cosens and L.L. Theriault, 1976. Teratogenic effects of magnesium deficiency in rats. J. Nutr., 106: 1254~1260. Hytten, F.E. and I. Leitch, 1971. The Physiology of Human Pregnancy. Blackwell Scientific Publications, Oxford. Jameson, S., 1976. Effects of zinc deficiency in h u m a n reproduction. Acta Med. Scand., Suppl., 593: 5 20. Kiilholma, P., R. Paul, P. P a k a r i n e n and M. Gronroos, 1984. Copper and zinc in pre-eclampsia. Acta Obstet. Gynecol. Scand., 63: 62~631. Kundu, N., P. Parke, L.P. Petersen, I.S. Palmer and O. Olson, 1985. Distribution of serum selenium, copper, and zinc in normal h u m a n pregnancy. Arch. Environ. Health, 40: 268-273. Lazebnik, N., B.R. Kuhnert, P.M. Kuhnert and K.L. Thompson, 1988. Zinc status, pregnancy complications, and labor abnormalities. Am. J. Obstet. Gynecol., 158: 161-166. Meadows, N.J., M.F. Smith and P.W.N. Keeling, 1981. Zinc and small babies. Lancet, ii: 1135~1136. Metcoff, J., J.P. Costiloe, W. Crosby, L. Bentle, D. Seshachalam, H.H. Sandstead, C.E. Bodwell, F. Weaver and P. McClain, 1981. Maternal nutrition and fetal outcome. Am. J. Clin. Nutr., 34: 708~721. Mimounij, F., M. Miodovnik, R.C. Tsang, J. Holroyde, P.S. Dignan and T.A. Siddiqi, 1987. Decreased maternal serum magnesium concentration and adverse fetal outcome in insulindependent diabetic women. Obstet. Gynecol., 70: 85-88.
76 Olatunbosun, D.A., F.A. Adeniyi and B.K. Adadevoh, 1975. Serum calcium, phosphorus and magnesium levels in pregnant and non-pregnant Nigerians. Br. J. Obstet. Gynaecol., 82: 568571. O'Leary, J.A., G.S. Novalis and G.J. Vosburgh, 1965. Maternal serum copper concentrations in normal and abnormal gestations. Obstet. Gynecol., 2: 112-117. Pitkin, R.M., 1985. Calcium metabolism in pregnancy and the perinatal period: a review. Am. J. Obstet. Gynecol., 151: 99-109. Prema, K., 1980. Predictive value of serum copper and zinc in normal and abnormal pregnancy. J. Med. Res., 71: 554-560. Ramanathan, J., B.M. Sibai, R. Pillai and J.J. Angel, 1988. Neuromuscular transmission studies in preeclamptic women receiving magnesium sulfate. Am. J. Obstet. Gynecol., 158: 40-46. Roelofsen, J.M.T., G.M. Berkel, O.T. Uttendorfsky and J.F.G. Slegers, 1988. Urinary excretion rates of calcium and magnesium in normal and complicated pregnancies. Eur. J. Obstet. Gynecol., 27: 227-236. Schenker, J.G., E. Jungreis and W.Z. Polishuk, 1969. Serum copper ltwels in normal and pathologic pregnancies. Am. J. Obstet. Gynecol., 105: 933-937. Sheldon, W.L., M.O. Aspillaga, P.A. Smith and T. Lind, 1985. The effects of oral iron supplementation on zinc and magnesium levels during pregnancy. Br. J. Obstet. Gynaecol., 92: 892-898. Smith, J.C., G.P. Butrimovitz and W.C. Purdy, 1979. Direct measurement of zinc in plasma by AAS. Clin. Chem., 24: 1487-1491. Spatling, L. and G. Spatling, 1988. Magnesium supplementation in pregnancy. A double-blind study. Br. J. Obstet. Gynaecol., 95: 120-125. Swanson, C.A. and J.C. King, 1987. Zinc and pregnancy outcome. Am. J. Clin. Nutr., 46: 763-771. Taufield, P.A., K.L. Ales, L.M. Resnick, M.L. Druzin, J.M. Gertner and J.H. Laragh, 1987. Hypocalciuria in preeclampsia. N. Engl. J. Med., 316: 715-718. Thurnau, G.R., D.B. Kemp and A. Jarvis, 1987. Cerebrospinal fluid levels of magnesium in patients with preeclampsia after treatment with intravenous magnesium sulfate: A preliminary report. Am. J. Obstet. Gynecol., 157: 1435-1438. Turkington, V.E. and A.A. Naji, 1985. Concentrations of Mg and Ca in serum are correlated in normal individuals. Clin. Chem., 31: 501-502. Tuttle, S., P.J. Aggett, D. Campbell and I. MacGillivray, 1985. Zinc and copper nutrition in human pregnancy: a longitudinal study in normal primigravidae and in privigravidae at risk of delivering a growth retarded baby. Am. J. Clin. Nutr., 41: 1032-1041. Villar, J., J.M. Belizan and P. Fischer, 1983. Epidemiological observations on the relationship between calcium intake and eclampsia. Int. J. Gynecol. Obstet., 21: 271-278. Vivoli, G., P. Borella, M. Bergomi and G. Fantuzzi, 1987. Zinc and copper levels in serum, urine, and hair of humans in relation to blood pressure. Sci. Total Environ., 66: 55~4. Wells, J.L., D.K. James, R. Luxton and C.A. Pennock, 1987. Maternal leucocyte zinc deficiency at start of third trimester as a predictor of fetal growth retardation. Br. Med. J., 294: 1054-1056. Wibell, L., M. Gebre-Medhin and G. Lindmark, 1985. Magnesium and zinc in diabetic pregnancy. Acta Paediatr. Scand., Suppl., 320: 100-106.
67
MATERNAL PLASMA CONCENTRATIONS OF MAGNESIUM, CALCIUM, ZINC AND COPPER IN NORMAL AND PATHOLOGICAL PREGNANCIES
P. BORELLA1'*, A. SZILAGYI2, G. THAN2, I. CSABA2, A. GIARDINO1 and F. FACCHINETTI~ llstituto di Igiene, Universita' degli Studi di Modena, Via Carnpi 287, 1-41100 Modena (Italy) 2Pecs Medical School, Department of Obstetrics and Gynecology, H-7643 Pecs (Hungary) 3Istituto di Ostetricia e Ginecologia, Universita" degli Studi di Modena, Via del Pozzo, 1-41100 Modena (Italy)
(Received October 12th, 1989; accepted January 17th, 1990)
ABSTRACT In this study, plasma levels of magnesium, calcium, zinc and copper were simultaneously determined in pregnancies complicated by either abortion, intrauterine growth retardation (IUGR), diabetes or EPH (edema, proteinuria, hypertension) gestosis. The levels of the four cations in non-pregnant women and in healthy, pregnant women were also determined. Compared with controls, a significant decrease in magnesium, with increase of the Ca/Mg ratio, was found in spontaneous abortions, but not when patients had a successful continuation of pregnancy. In EPH gestosis, total calcium was reduced, with a significant decrease of the plasma Ca/Mg ratio. A slight, but significant, increase in plasma zinc was observed in women affected by either diabetes or IUGR, probably as a result of reduced zinc uptake by the fetus. In addition, higher copper levels were found in the pathologies studied, with the exception of missed abortions. The possible role of an altered Ca/Mg ratio homeostasis in relation to gestational pathologies is discussed.
INTRODUCTION It has been r e c o g n i z e d t h a t c h a n g e s in m i n e r a l m e t a b o l i s m could h a v e a h a r m f u l effect on fetal g r o w t h (Pitkin, 1985; Adeniyi, 1987; S w a n s o n a n d King, 1987). The r e c e n t l i t e r a t u r e indicates t h a t a l t e r a t i o n s in p l a s m a a n d cellular zinc are a s s o c i a t e d with v a r i o u s obstetric p a t h o l o g i e s (Tuttle et al., 1985; Wibell et al., 1985; Wells et al., 1987; L a z e b n i k et al., 1988). I n addition, plasma m a g n e s i u m was f o u n d to decrease d u r i n g a b n o r m a l g e s t a t i o n (Wibell et al., 1985; M i m o u n i et al., 1987; Ajayi, 1988), and the effect of m a g n e s i u m supplem e n t a t i o n on the o u t c o m e of p r e g n a n c y has been e x a m i n e d ( T h u r n a u et al., 1987; R a m a n a t h a n et al., 1988; S p a t l i n g a n d Spatling, 1988). A b n o r m a l i t i e s in c a l c i u m r e g u l a t i o n h a v e been r e p o r t e d in b o t h diabetes (Godeny et al., 1986; Belizan et al., 1988; Roelofsen et al., 1988) a n d pre-eclampsia (Taufield et al., 1987); c h a n g e s in p l a s m a copper h a v e also been observed (HeijkenskjSld and *Author to whom requests for reprints should be addressed.
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© 1990- - Elsevier Science Publishers B.V.
68
Hedenstedt, 1962; O'Leary et al., 1965; Bodgen et al., 1978; Metcoff et al., 1981; Kiilholma et al., 1984). Data on cation patterns in pregnancy are conflicting; in only a few cases was more than one cation determined, thus a sufficiently adequate description of the mineral levels in different complications in human pregnancy is lacking. In this study, we simultaneously determined zinc, copper, magnesium and calcium in plasma of pregnant women in relation to either abortion, diabetes, gestosis or intrauterine growth retardation (IUGR), in order to clarify the association between altered mineral levels and pregnancy disorders of the first and third trimester. The results are compared with those obtained for controls with uncomplicated pregnancies. In addition, the levels of the four cations in non-pregnant women were determined, in order to compare them with those found in healthy, pregnant women. MATERIALSAND METHODS In total, 84 hospitalized, pregnant women suffering from complications were recruited. Twenty-four patients were studied at first trimester (6--16 weeks of gestation) with threatened abortion: 12 underwent interruption of pregnancy. In these cases, blood samples were taken after ultrasound scan and urinary hCG tests, 1 2 days before dilatation and curettage. For the remaining patients, pregnancies continued, and embryo well-being was monitored with ultrasound scan and urinary hCG excretion for at least 1 month to rule out missed abortion. Sixty patients were studied at the third trimester (between 29 and 40 weeks of gestation). They suffered from diabetes (n = 18), intrauterine growth retardation (n = 18) and EPH (edema, proteinuria, hypertension) gestosis (n = 24). Diabetic patients were mainly insulin-dependent diabetics, with the exception of three patients with gestational diabetes. They were on a diet, or on prophylactic insulin treatment, and morning glucose levels were constantly maintained between 4 and 6mmoll 1. In these cases, blood samples were collected in the morning, 1.5h after insulin injection. Birth weights ranged between 2340 and 4210 g. Diagnosis of IUGR was made with the help of ultrasound scan and biochemical monitoring (hPL and pregnancy specific Bl-glycoprotein SP1) performed in the 34th and 37th week. Termination of pregnancy occurred between 38 and 42 weeks in all cases, with the exception of three patients who delivered in the 35th, 36th and 37th week of gestation. Caesarian section was necessary in three cases and forceps were used in two cases. The therapy was 02 inhalation (81 min-1) and amino acids infusion. Birth weights ranged between 1930 and 2730 g, and were below the 10th centile. For patients with EPH gestosis, edema was present in all but two cases; proteinuria (> 300mg of urinary proteins per 24h) was found in 14 of 24 patients; and hypertension was present in all but three cases. Hypertension in
69 pregnancy was defined as the presence of a blood pressure of at least 140/ 90mm Hg or a rise of 30 mm Hg in systolic pressure or 15 mm Hg in diastolic pressure. Patients were treated with fl-blockers and K-sparing diuretics. Deliveries occurred at term in all but six cases, and birth weights were between 1100 and 3930g: five were under the 10th centile, and four were between the 10th and the 25th centile. The control group consisted of 100 healthy, pregnant women: 41 at first trimester, 24 at second and 35 at third. None of them suffered from any pregnancy complication in either the prenatal or the perinatal period. Age, pre-pregnancy weight, weight gain and parity were similar between controls and patients. In addition, a group of 21 non-pregnant women aged 24-37 years were examined for the same cations, in order to define non-pregnant levels. Blood was collected from each participant in the fasting state, and plasma was obtained after centrifuging heparinized blood at 1200g for 10 min at 4°C. Particular attention was paid to avoid blood haemolysis and metal contamination during blood collection by using stainless steel needles and plastic syringes. Disposable plastic test-tubes were used whenever possible and all glassware was soaked in dilute hydrochloric acid solution for at least 16 h, then rinsed with demineralized, double-distilled water. No metal release was observed from tubes or materials. Zinc and copper were determined by flame atomic absorption spectrophotometry (AAS) following the procedure of Smith et al. (1979). The method of standard additions was used to check plasma results, as previously described (Vivoli et al., 1987). For magnesium and caleium analyses, plasma was diluted with 0.1% lanthanum chloride solution. Appropriate magnesium and calcium standards were prepared in the same diluent solution. Accuracy was determined by adding 0.5-2.0mmolMgl 1 and 2.(~4.0mmolCal-1. The recovery ranged from 98.2 to 101.2% for both cations. The precision, calculated on 10 replicates, was high (< 2%). A Perkin-Elmer AAS Model 5000 equipped with an air-acetylene flame was used for all determinations, making instrument adjustments according to the manufacturer's instruction manual. Statistical analyses were carried out using Student's t test and linear correlation coefficients. All cations were normally distributed, thus non-log transformation of data was performed before statistical treatment. RESULTS Plasma levels of the four cations in normal pregnancies, and in non-pregnant women, are shown in Fig. 1. A progressive decrease in plasma zinc was observed throughout pregnancy, whereas the reverse was found for copper. Magnesium and calcium reached their lowest level during the second trimester, with a slight, but insignificant, increase in the third trimester. When patients suffering from threatened abortion or spontaneous abortion
70 HEALTHY PREGNANT WOMEN ,:3.0
b
[~]
2.5
non-pregnant
[]first []second I
2.0
trim. tr~m.
third trim.
4. E 1.o
.5
o Calcium
5"0'
m Magnesium
a
45
apc
4.0 ¸ 35 ¸ ,~0 ¸
< 25 ¸ 20 ¸ 15 ¸ 10 5 0 Copper
Zinc
Fig. 1. P l a s m a c o n c e n t r a t i o n s of t h e four c a t i o n s in n o n - p r e g n a n t and healthy, p r e g n a n t women. (a) p < 0.001, (b) p < 0.05 compared with n o n - p r e g n a n t women, (c) p < 0.01 b e t w e e n first and second trimester, (d) p < 0.01 b e t w e e n second and t h i r d trimester. TABLE 1
P l a s m a magnesium, calcium, zinc and copper c o n c e n t r a t i o n s (mean _+ SD) of p a t i e n t s suffering from abortion or t h r e a t e n e d abortion First t r i m e s t e r Controls (n = 41) M a g n e s i u m (mmol1-1) Calcium (mmoll -~) Zinc ~ m o l l
i)
Copper ~ m o l 1 - 1 ) *p < 0.02; ***p < 0.001.
0.80 + 0.11
Abortion (n = 12) 0.67 + 0.13"**
T h r e a t e n e d abortion (n = 12) 0.75 _+ 0.07
2.43 _+ 0.32
2.38 + 0.26
13.13 _+ 2.37
13.64 _+ 2.35
11.31 _+ 2.11"
2.30 +
0.32
26.05 _+ 6.53
28.22 + 4.68
46.53 +_ 13.18"
71 w e r e c o n s i d e r e d (Table 1), p l a s m a m a g n e s i d m w a s significantly r e d u c e d in women undergoing pregnancy termination when compared with healthy c o n t r o l s of s i m i l a r g e s t a t i o n a l period (p < 0.001). P a t i e n t s h a v i n g a successful c o n t i n u a t i o n of p r e g n a n c y s h o w e d l o w e r levels of zinc a n d h i g h e r levels of c o p p e r w i t h r e s p e c t to c o n t r o l s a n d to p a t i e n t s w i t h a b o r t i o n . T h e p l a s m a levels of the f o u r c a t i o n s in t h i r d t r i m e s t e r p a t i e n t s are g i v e n in T a b l e 2, a n d are c o m p a r e d w i t h c o n t r o l s at a s i m i l a r g e s t a t i o n a l period. P l a s m a c a l c i u m w a s s i g n i f i c a n t l y r e d u c e d in e c l a m p t i c patients, w h e r e a s o n l y a slight d e c r e a s e of this c a t i o n was o b s e r v e d in p a t i e n t s w i t h I U G R . T h e zinc conc e n t r a t i o n for p a t i e n t s w i t h d i a b e t e s or I U G R w a s s i m i l a r to t h a t for c o n t r o l s a t second t r i m e s t e r (11.32 + 2 . 3 0 # m o l l 1), a n d s i g n i f i c a n t l y h i g h e r t h a n t h a t f o u n d at t h i r d t r i m e s t e r . S i g n i f i c a n t i n c r e a s e s of c o p p e r w e r e o b s e r v e d in all g r o u p s of p a t i e n t s . T h e r e s u l t s did not c h a n g e w h e n e c l a m p t i c p a t i e n t s w h o delivered a g r o w t h r e t a r d e d n e o n a t e (n = 5) w e r e included in the I U G R group. No v a r i a t i o n in m e a n p l a s m a m a g n e s i u m b e t w e e n g r o u p s w a s observed. H o w e v e r , w h e n p a t i e n t s w e r e subdivided a c c o r d i n g to l u n a r m o n t h (29-32 weeks, 33-36 weeks, 37-41 weeks), a slight, b u t significant, r e d u c t i o n of m a g n e s i u m was o b s e r v e d for b o t h d i a b e t e s (0.68 + 0.07 m m o l 1-1) a n d I U G R (0.69 + 0 . 1 0 m m o l l - 1 ) , b o t h e x a m i n e d at 29-32 w e e k s w i t h r e s p e c t to c o n t r o l s (0.78 _+ 0 . 0 9 m m o l l - l , p < 0.05). T h e m o l a r C a / M g r a t i o w a s c a l c u l a t e d , a n d it was f o u n d to be fairly c o n s t a n t in n o n - p r e g n a n t w o m e n (3.14 _+ 0.21) and t h r o u g h o u t p r e g n a n c y : 3.07 + 0.33 at first t r i m e s t e r , 3.21 _+ 0.36 at t h e second, 3.19 + 0.24 at the third. T h e m o l a r C a / M g r a t i o s a r e i l l u s t r a t e d in Fig. 2. A significant i n c r e a s e is o b s e r v e d w i t h a b o r t i o n s , w h e r e a s in p a t i e n t s w i t h E P H gestosis the C a / M g r a t i o was l o w e r t h a n in c o n t r o l s (2.86 vs 3.19, p < 0.05). TABLE 2 Mean plasma content (mean + SD) of the examined cations in women with diabetes, growth retardation and pre-eclampsia/toxemia Third trimester Magnesium (mM1-I)
Calcium (raM1-1)
Controls (n = 35)
0.75 _+ 0.07
2.39 _+ 0.23
Diabetes (n = 18)
9.76 + 0.n/
2.40 _+ 0.28
11.73 _+ 1.80"**
51.95 + 7.45***
Growth retardatiol (n = 16)
0.76 _+ 0.14
2.26 _+ 0.30
11.70 + 1.83"**
54.56 _+ 8.79***
Pre-eclampsia/ toxemia (n = 24)
0.77 _+ 0.11
2.15 + 0.26***
10.49 + 2.28
51.78 + 19.16"*
**p < 0.01; ***p < 0.001.
Zinc (uM1-1) 9.60 + 2.29
Copper (,uM1-I) 40.34 _+ 8.85
72 Ca/Mg Ratio
F-
Control=
]
Abo~on T h r e o t e n e d Abort,
Control~ D|obetes IUGR EPH-Gestosis
]
*
0 .:,:o '2:o '3:o ',:o '5:0 Fig. 2. Plasma Ca/Mg molar ratio in patients and controls; *p < 0.01.
When the molar Cu/Zn ratios were calculated, we found no difference between patients and controls, with the exception of subjects suffering from threatened abortion. In those cases, the molar Cu/Zn ratio was 4.41 compared with 2.07 for controls (t = 4.73, p < 0.001). Correlation coefficients were determined between the measured parameters, and we found a high positive correlation between magnesium and calcium in the control group at both first and last trimester (r = 0.71,p < 0.001), whereas there was no such correlation for the patients. No other correlations were found between the cations examined, nor between cations and birth weights. DISCUSSION
We have determined plasma concentrations of zinc, copper, calcium and magnesium, modifications of which have been implicated in the interference of normal pregnancy development. The trends of the four cations in normal pregnancies are in agreement with other findings (Olatunbosun et al., 1975; Kundu et al., 1985; Sheldon et al., 1985; Ajayi, 1988), and the range of values is comparable to those in the literature (Schenker et al., 1969; Hambidge and Droegemueller, 1974; Meadows et al., 1981; Campbell-Brown et al., 1985; Pitkin, 1985). The measurements were carried out for four different pathological conditions, and the most interesting findings are: (i) A decrease in plasma magnesium, with a concomitant increase in the Ca/Mg ratio, with abortions; (ii) A decrease in plasma calcium and the Ca/Mg ratio in patients with EPH gestosis; (iii) An increase in plasma copper and zinc in subjects suffering from diabetes or IUGR.
73 Compared with controls, lower mean plasma magnesium levels (17% lower) were found in patients experiencing an abortion, but not when the abortion was only threatened, and the pregnancy successfully continued. In recent experimental studies, magnesium deficiency has been shown to increase significantly both fetal loss rate and teratogenicity (Hurley et al., 1976), and the threshold maternal serum magnesium level for embryotoxic effect was found to be ~ 24% below the control value (Gfinther et al., 1981). Indeed, in the present study, five of 12 women undergoing a first trimester abortion had a plasma magnesium level 24% below the mean value of the control group. Furthermore, a high incidence of abortion in diabetics with low serum magnesium has been reported (Mimouni et al., 1987). Thus a causal relationship between magnesium deficiency and spontaneous abortion deserves to be evaluated further. On the other hand, we could not find any difference in magnesium levels when patients with EPH gestosis and IUGR were examined, in agreement with other studies (Boston et al., 1989). Although magnesium therapy has been associated with a reduction in maternal and fetal morbidity, it was not effective against pre-eclampsia or fetal growth retardation (Spatling and Spatling, 1988). On the contrary, preliminary findings on amniotic fluid levels seem to associate IUGR with increased fetal magnesium excretion (Facchinetti et al., 1989). In patients suffering from EPH gestosis, there was a reduction in plasma calcium, thus supporting the hypothesis of an association between calcium metabolism and pregnancy-induced hypertension (Taufield et al., 1987; Belizan et al., 1988). The mechanism involved is unknown, although it was hypothesized that both reduced parathyroid hormone secretion and increased calcium excretion through the urinary system could play a role (Belizan et al, 1983). According to epidemiological data, the incidence of eclampsia was found to vary inversely with calcium intake (Villar et al., 1983), and both oral calcium and magnesium supplementation have been reported to decrease the incidence of pre-eclampsia and to lower blood pressure (Belizan et al., 1983). Despite the existence of significant changes in both magnesium and calcium levels during pregnancy, their molar ratio was fairly constant both in non-pregnant women and throughout pregnancy. Furthermore, the relationship between calcium and magnesium observed in healthy pregnancies disappeared in pathological groups, as reported for other pathological conditions (Turkington and Naji, 1985; Chueca et al., 1987). Our results suggest that, in addition to the absolute concentrations of the two cations, their ratio and the relationships between the two metals might be of particular interest as indices of abnormal gestation. A high Ca/Mg ratio has been experimentally shown to provoke vasospasm in certain blood vessels in vitro, and it has been suggested that this is responsible for the spasm of umbilical and placental vasculature in normal women at the end of pregnancy (Altura et al., 1983). In our study, a higher than normal Ca/Mg ratio in plasma was found with abortions, whereas the ratio was reduced in patients with EPH gestosis. The limited number of women examined does not allow any definitive conclusion, but the role of
74 Ca/Mg homeostasis during obstetric pathologies requires further consideration. The finding of higher levels of zinc in patients carrying a growth-retarded fetus is in agreement with other studies (Cherry et al., 1981; Metcoff et al., 1981), although the opposite trend has also been observed (Jameson, 1976). The decrease in plasma zinc after 14 weeks gestation could be considered physiological, being secondary to plasma volume expansion, which is in turn related to birth weight (Hytten and Leitch, 1971; Tuttle et al., 1985). Indeed, a reduced plasma volume response to pregnancy has been observed in a number of women who delivered growth-retarded babies (Tuttle et al., 1985). Unfortunately, we could not measure plasma volume, and a clear correlation with birth weight was not determined. More than one factor, and particularly a higher fetal uptake of zinc, might be involved in the trend of this cation during the third trimester. It is worth noting that the values we found in diabetes and growth retardation at third trimester are similar to those found in the second trimester of the control pregnancies. Thus, in abnormal gestations, both reduced plasma expansion and/or reduced transfer of this cation to the fetus might be the reason for the higher zinc levels in maternal plasma at third trimester. In studies of diabetics, non-pregnant, insulin-dependent diabetics and those in early pregnancy had lower levels of zinc and magnesium than controls. For zinc, there was no difference at delivery, whereas a difference in serum magnesium persisted during pregnancy (Wibell et al., 1985). In our study group, a slight reduction in magnesium was found only during the seventh month of gestation. This finding agrees with the conclusion that, for well-regulated diabetic women, the relatively small deviation of magnesium from control levels should not be over-estimated. A high plasma copper concentration seems to be a common feature in women suffering from either pre-eclampsia, or diabetes and threatened abortion, confirming the observations of other authors (Heijkenskjold and Hedenstedt, 1962; Schenker et al., 1969; F a t t a h et al., 1976; Godeny et al., 1986), although the opposite trend has also been reported (Hiilholma et al., 1984). It has been suggested that high serum copper could be found in women with hyperactive placentas and lower values in women having placental insufficiency (Prema, 1980), although our data are inconsistent with such a hypothesis. To clarify our findings, the relationship between copper and hormonal trends, including insulin levels, requires further evaluation, taking into account the possible interfering effect of therapy on copper. REFERENCES Adeniyi, F.A.A., 1987. The implications of hypozincemiain pregnancy. Acta Obstet. Gynecol. Scand., 66: 579-587. Ajayi, G., 1988. Serum magnesiumconcentration in premenopausal, menopausal women, during normal and EPH-gestosis pregnancy and the effect of diuretic therapy in EPH-gestosis. Magnesium Bull., 10:72 76.
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