Pregnancy Estrogens in Relation to Coffee and Alcohol Intake Eleni Petridou, MD, MPH, Klea Katsouyanni, DMSc, Evangelos Spanos, MD, PhD, Yannis Skalkidis, MD, MPH, Kelly Panagiotopoulou, MD, and Dimitrios Trichopoulos, MD Total estrogen (TE) , es~r~o~(EZ}, estrioi (E3), and hu~n p~en~ lactogen fhPL) levels were determined by radioimmunoassay in the Hood of 14 I pregnant women during their 26th and 3 I st weeks of pregnancy and the results were studied in relation to coffee and alcohol intake. After con~o~~~ngfor ~~ age, ~~~ weight at the c~es~~~ng week of ~re~ncy, purity, and tobacco smoking, as well as for mutuaf confounding effects, cojfee intake, ascertained at the 26th week, was found to be negatively related to pregnancy E2 levels (P = 0.04 during the 26th week, and P = .I6 during the 3 1st week), whereas alcohol intake, also ascertained at the 26th week, evas found to be positively related to pregnancy TE levels (P = .04 during the 26th week, and P = I I8 during the 3 Jst week). The negative relation between coffee consumption on the one hand and E2 (and possibly TE) levels on the other may be responsible for the inverse association between ~te~J coffee intake and birth weight; the latrer ~soc~ution ha.5been repea~~y confirmed in the literature, although it was neither strong nor statistically s&n&ant in the present study. The relations of maternal coffee and alcohol consumption with pregnuncy estrogen levels, if confirmed, could be utilized in studies exploring the role offers exposure to these hormones in the etiology of gonada! germ-cell tumors and possibly other diseases. Ann Epidemiol I992 ;2: 24 f-247. KEY WORDS:
Pregnancy estrogens, coffee intake, alcohol intake, gonadal tumors, breast
cancer.
INTRODUCTION There are several reasons to examine whether coffee and alcohol intake during preg nancy affects pregnancy estrogen levels. First, there is converging evidence from several large human studies that coffee consumption, even in modest quantities, is associated with low birth weight (l-4). A similar but stronger association between tobacco smoking during pregnancy and birth weight (S-8) has been attributed (9) to tobacco effects on pregnancy estrogen levels (9, lo), raising the possibility that an analogous mechanism may be responsible for the association between maternal coffee intake and birth weight. Second, maternal alcohol intake has dose-dependent prenatal effects in both humans and experimental animals (mainly Sprague-Dawley rats) ( 1 l), but these ate neither predictable nor adequately explained, allowing speculations that invoke female reproductive hormones (not necessarily estrogens) (11). Third, pregnancy estrogens have been implicated by several authors in the etiology of a number of malignancies, including testicular cancer ( 12, 13), ovarian germ-cell tumors (14), and possibly breast cancer (15). Given the rarity of these tumors, epidemiologic assessment of the corresponding hypotheses will depend, to a considerable extent, on the identification
From the Department of Hygiene and Epidemiology, University of Athens Medical School (E. P., K. K., Y. S., K. P.) and Biomedicine Laboratories (E. S. ), Athens, Greece, and the Department of Ep~demiolo~, Harvard School of Public Health, Boston, MA (D. T.). Address reprint requests to: Dimitrios Trichopoulos, MD, Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115. Recewed December 12, 1990; revised May 21, 1991. Q 1992 Elsevier Scw~ce Putdishing Co.,
Inc.
1047~2797/92/$05.00
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of correlates or determinants of pregnancy estrogens. Coffee and alochol intake may or may not be determinants of pregnancy estrogens, but they are highly repeatable in dietary histories and, therefore, suitable factors for epidemiologic investigation. In this report we examine whether moderate coffee and alcohol intake during pregnancy affects blood levels of total estrogens (TE), estradiol (EZ), and total estriol (E3). Human placental lactogen (hPL) was also measured for exploratory purposes.
MATERIALS
AND
METHODS
During the first 6 months of 1987, 177 women were randomly chosen among those attending the outpatient maternity clinic of a major university hospital in Athens. Two groups of women were included: those who were smokers throughout their index pregnancies, and those who have never smoked regularly during their lives and not at all during these pregnancies. Once or twice per week during the study period, the same investigator (K. I’.) visited the maternity clinic and requested permission to interview and take blood samples from pregnant women attending the clinic. The objective was to have adequate numbers of women to assess the effects, if any, of tobacco smoking, coffee drinking, and alcohol intake. Since smoking during pregnancy is rare, whereas light and moderate coffee and alcohol drinking is not, all identified smokers were asked to participate, whereas only the first two or three nonsmoking women during every visit were contacted. Women with a twin pregnancy, diabetes mellitus, hypertension, thyroid disease, and chronic use of any medication for whatever reason at any time during this pregnancy were not asked to be part of the study; all study pregnancies led to normal live births. A total of 141 women agreed to participate (80%); among them, 49 were smokers and the remaining 92 never smoked regularly in their lives. Morning blood samples were taken from these women during the 26th and 31st week of their pregnancies; the 26th week was chosen because at that time, TE levels are midway through their gestational age-dependent increase. Measurements were taken during the 31st week of pregnancy in order to assess whether the patterns observed are reasonably consistent, since TE levels show little increase between the 26th and 31st weeks (16, 17). E2, E3, TE, and hPL levels were determined by radioimmunoassay. The TE assay (Radioassay Systems Laboratories, ICN Biomedicals, Carson, CA) detects the additive concentration of unconjugated estradiol-17/3 and estrone (El); it does not detect any of the estrogen sulfates and glucuronides, and does not distinguish among free El, E2, and E2 bound to circulating binding proteins. TE measurements are considered an approximation of plasma estrogenicity. The E2 assay (Leeco Diagnostics, Southfield, MI) detects total serum E2 level, the majority of which is bound to sex hormone-binding globulin. E2 is biologically the most potent among the estrogens. The E3 assay (RADIM, Pomezia, Rome, Italy) measures free estriol together with conjugates that are hydrolyzed by a mixture of enzymes (glucuronidase and sulfatase). Finally, the hPL assay (RADIM, Pomezia, Rome, Italy) measures the polypeptide hormone that has a short in piivo half-life and is more useful in serial measurements. On the basis of 15 blind duplicate measurements, the coefficients of variation of the assay procedures were calculated to be 4% for TE, 10% for E2, 3% for E3, and 8% for hPL. All measurements were performed at Biomedicine Laboratories (Athens, Greece) under the direction of one of us (E. S.) (9, 18). A detailed questionnaire was administered to each woman by one of us (K. I’.) at the time of the first blood drawing. The questionnaire covered socioeconomic, anthropometric, dietary, and medical variables, as well as details about tobacco smok-
Petridou et al. PREGNANCY ESTROGENS, COFFEE, AND ALCOHOL
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TABLE alcohol
243
1 Distribution of women by age, parity, weight at delivery, smoking status, intake, and coffee consumption during pregnancy Variable
Age (~1 5 19 20-24 25-29 2 30 Parity First pregnancy Second pregnancy Weight at delivery (kg) 1st quartile (566) 2nd quartile (67-72) 3rd quartile (73-80) 4th quartile (~81) Smoking during pregnancy (cigarettes/d) Nonsmokers I-10 Z-11 Alcohol consumption during pregnancy Nondrinkers Drmkersb Coffee consumption during pregnancy Nondrinkers 5 1 cup/d > 1 cup/d
n
W)
10
( 7.1)
51
(36.2) (31.9) (24.8)
45 35 65 75
(46.4) (53.6)
34 34
(24.8) (25.6) (24.8) (24.8)
92 29 20
(65.2) (20.6) (14.2)
89 51
(63.6) (36.4)
40 54 46
(28.6) (38.6) (32.9)
34 35
y Four women in thex third pregnancy were included among those in their second pregnancy. b Includes women drinking from 2 glasses of alcoholic beverages per week up to 2 glasses per day.
ing and drinking of coffee and alcoholic beverages. Alcohol intake was measured in glasses of alcoholic beverages; glasses of alcoholic beverages contain usually the same amount of ethanol, because beverages with a high alcohol content are drunk in smaller quantities (and glasses) (11). Coffee consumption was measured in cups per day; all but a few of the women were drinkers of Greek (Turkish) coffee, which is known to contain about half the caffeine found in regular American coffee (19). The statistical analysis was done through standard multiple regression (20). When pregnancy hormones were considered as dependent variables, natural logarithmic transformation was utilized. In this instance, anti-logs of the partial regression coefficients indicate proportional changes. Because of missing values for one or more variables, analyses were frequently based on less than 141 of the participating women but in no instance on fewer than 131 of them.
RESULTS Table 1 shows the distribution of the women by the study variables. There were no heavy drinkers of either alcoholic beverages or coffee in this group (no woman was drinking more than 5 cups of Greek coffee per day or more than 2 glasses of alcoholic beverages per day). Virtually all drinkers were wine consumers.
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TABLE 2 Multiple regression-derived” proportional changes (and 95% confidence intervals) of serum hormone levels contrasting alcohol drinkers to nondrinkers and women in three consecutive groups with increasing daily coffee intake (nondrinkers, drinkers of up to 1 cup/d, drinkers of more than 1 cup/d) Estradiol
Estriol
Total estrogens
Placental lactogen
26th week of pregnancy
Alcohol consumption
10 (-6,
Coffee consumption
P = .23 -10 (-19, P = .04
3 1st week of pregnancy Alcohol consumption Coffee consumption
29) 1)
13 (-4, 32) P = .16 -7 (-17, P = .16
3)
l(-12, 15) P = .87 l (-8, 10) 1 = .92
-9 (-17, P = .08
20 (5, 38) P = .Ol -2 (-10, 8) P = .70
13 (-5, 15) P = .18 0 (-11, 13) P = .99
17 (1, 35) P = .04
-13 (-27, P = .I1 1)
3)
-3 (-14, P = .61
9)
-3 P = -3 P =
8)
(-12, .57 (-9, .41
4)
r Controlling for maternal age, maternal weight at the corresponding week, panty. t&acco Fmokmg, and (mutually) coffee and alcohol Intake.
Table 2 examines the effects of alcohol and coffee drinking during pregnancy on E2, E3, TE, and hPL levels, controlling for maternal age, maternal weight (at the corresponding week), parity, tobacco smoking, and (mutually) alcohol and coffee intake. With respect to hPL, there is no consistent pattern of relation with either alcohol intake or coffee intake. However, there is evidence that alcohol intake is positively related to serum E2 and TE levels, whereas coffee intake appears to be negatively related to E2 levels. Table 3 summarizes the results from multiple regression modeling of birth weight on a number of known or possible predictors (maternal age, maternal weight at delivery, parity, tobacco smoking) as well as on alcohol and coffee consumption. Children born to younger and heavier women have a higher birth weight and, as expected, tobacco smoking is associated with reduced birth weight. By contrast, neither alcohol nor coffee consumption, at the ranges examined in the present study, had a significant effect on birth weight (P > .50 in both instances).
TABLE 3 Multiple regression-derived regression coefficients (b) and standard errors (SE(b)) of birth weight (in g) on maternal age, maternal weight at delivery, parity, tobacco smoking, and coffee and alcohol consumption Units or categories
Variable Age Maternal Parity
lzg weight at delivery Primiparvus:
0
Tobacco smoking
Multlparoux Nonsmoker:
I @
Alcohol
I-10 cigarettes/d: 2 11 cigarettes/J: Nondrinkers: 0
consumption
Coffee consumption
Drinkers: 1 Nondrinkers: I
>
I cup/d: I 1 cup/d: 2
0
b
SE(b)
P
- 18.7
7.6 4.0 77.1
.02 .02 .77
38.9
.03
79.0
.52
52.5
.89
9.4 22.2 -85.0 1 2 51.0 -7.1
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Petridou et al. PREGNANCY ESTROGENS,
245
COFFEE,AND ALCOHOL
DISCUSSION In this study, moderate coffee consumption was not significantly associated with birth This was not unexpected. Variability of birth weight among full-term newborns is not as large as the variability of pregnancy estrogens ( 16, 17); the association between coffee intake and birth weight is relatively weak (4); and the previous studies that have demonstrated this association included several thousand subjects (l-3). Furthermore, the confidence interval derived from the present study covers the corresponding point estimates of all major studies exploring the relation between coffee intake during pregnancy and birth weight (4). The present investigation is the first to examine whether maternal coffee intake is associated with pregnancy estrogen levels. The results are not conclusive but do suggest that a negative association exists. Since estrogens are established growth factors (21) and appear to be positively related to birth weight (9), the negative association between coffee intake and pregnancy estrogen levels could provide a plausible explanation for the negative association between coffee intake and birth weight (l-4). An analogous mechanism appears to exist with respect to maternal tobacco smoking (9, 10) and may explain the apparently additive effects of maternal coffee and tobacco consumption on birth weight (4). Several mechanisms have been postulated to explain the association between maternal smoking and birth weight, mostly focusing on placental structural changes, nutritional disturbances, and possibly direct effects of smoking on the embryo (22-24). Experimental studies probing effects of coffee on reproduction and prenatal toxicity have in general been inconclusive and no specific hypothesis has been advanced to explain the negative relation between maternal coffee consumption and birth weight (4). The evidence represented in this report integrates findings concerning both tobacco and coffee effects on birth weight in the context of the well-established growthenhancing effects of estrogens (2 1). With respect to alcohol, the data pertaining to pregnancy estrogen levels and birth weight are not clear-cut. There is strong evidence that alcoholism and alcohol abuse are associated with reduced birth weight (ll), but findings concerning the effects of alcohol consumption at the low levels considered in the present study are inconclusive; indeed, intake of up to 2 drinks per day during pregnancy was positively (although not significantly) associated with birth weight in the large study of Marbury and colleagues (25) and among nonsmokers in the recent study by Brooke and coworkers (8). Therefore, the results of the present study indicating that moderate alcohol consumption during pregnancy is positively related to levels of pregnancy TE are not incompatible with the postulated role of estrogens as an important intermediate pathway linking dietary and other exogenous factors to birth weight. It should be noted that in the present study, the relations of alcohol and coffee consumption with pregnancy estrogens were in general stronger during the 26th week than during the 3 1st week of pregnancy and more pronounced with respect to E2 and TE than with respect to E3. These findings may be accounted for by the fact that coffee and alcohol consumption was ascertained at the time of the first blood drawing during the 26th week, and by the widely supported evidence that the estrogenicity of E3 is limited and its overall biologic importance questionable (16, 17). It has been hypothesized that intrauterine exposure to high levels of endogenous tumors, including estrogens may also increase the risk of some hormone-dependent testicular cancer (12, 13), ovarian germ-cell cancer (14), and breast cancer (15).
weight.
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Likely predictors of levels of pregnancy estrogens, including severe nausea during pregnancy and maternal obesity (13, 14), maternal age (18) and birth order (18, 26, 27) have been examined as possible risk factors for gonadal germ-cell tumors and breast cancer. The identification of exogenous determinants of pregnancy estrogen levels would allow generation of additional variables that could be used as exposure indicators in epidemiologic studies.
This work was supported in Athens by a grant from the Greek Ministry of Health and in Boston by a grant to Harvard University from Mr. George S. Livanos.
REFERENCES 1. van den Berg BJ. Epidemiology observations of prematurity: Effects of tobacco, coffee and alcohol. In: Reed DM, Stanley FJ, eds. The Epidemiology of Prematurity. Baltimore, MD: Urban and Schwarzenberg; 1977:157-76. 2. Martin TR, Bracken MB. The association between low birth weight and caffeine consumption during pregnancy, Am J Epidemiol. 1987; 126:813-21. 3. Lin S, Schoenbaum SC, Monson RR, Rosner B, Stubblefield PC, Ryan KJ. No association between coffee consumption and adverse outcomes of pregnancy, N Engl J Med. 1982;306:141-5. 4. International Agency for Research on Cancer (IARC). IARC Monographs on Evaluation of Carcinogenic Risks to Humans. v. 51. Coffee, Tea, Mate, Methylxanthines and Methylglyoxal. Lyon: IARC; 1991: l-206. 5. Simpson WJ. A preliminary report of cigarette smoking and the incidence of prematurity, Am J Obstet Gynecol. 1957;73:808-15. 6. Bosley ARJ, Sibert JR, Newcombe RG. Effects of maternal smoking on fetal growth and nutrition, Arch Dis Child. 1981;56:727-9. 7. Gorton CC. Smoking during pregnancy, Del Med J. 1985;57:455-9. 8. Brooke GO, Anderson RH, Bland MJ, Peacock LS, Steward MC. Effects on birthweight of smoking, alcohol, caffeine, socioeconomic factors, and psychosocial stress, Br Med J. 1989;298:795-801. 9. Petridou E, Panagiotopoulou K, Katsouyanni K, Spanos E, Trichopoulos D. Tobacco smoking, pregnancy estrogens and birth weight, Epidemiology. 1990;1:247-50. 10. Bernstein L, Pike MC, Lobo RA, Depue RH, Ross RK, Henderson BE. Cigarette smoking in pregnancy results in marked decrease in maternal hCG and oestradiol levels, Br J Obstet Gynaecol. 1989;96:92-6. 11. International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. v. 44. Alcohol Drinking. Lyon: IARC; 1988:1-416. 12. Henderson BE, Benton B, Jing J, Yu MC, Pike MC. Risk factors for cancer of the testis in young men, Int J Cancer. 1979;23:598-602. 13. Depue RH, Pike MC, Henderson BE. Estrogen exposure during gestation and risk of testicular cancer, J Nat1 Cancer Inst. 1983;71:1151-5. 14. Walker AH, Ross RK, Haile RWC, Henderson BE. Hormonal factors and risk of ovarian germ cell cancer in young women, Br J Cancer. 1988;57:418-22. 15. Trichopoulos D. Hypothesis: Does breast cancer originate in utero?, Lancet. 1990;35:939-40. 16. Yen SSC. Endocrinology of pregnancy. In: Creasy RK, Resnic R, eds. Maternal-fetal Medicine. 2nd ed. Philadelphia: WB Saunders; 1989;375-403. 17. Lauritzen C, Klopper A. Estrogens and androgens. In: Fuchs F, Klopper A, eds. Endocrinology of Pregnancy. 3rd ed. Philadelphia: Harper and Row; 1983:73-91. 18. Panagiotopoulou K, Katsouyanni K, Petridou E, Garas Y, Tzonou A, Trichopoulos D. Maternal age, parity and pregnancy estrogens, Cancer Causes Control. 1990; 1: 119-24.
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19.
Rebelakos
A. Tobacco
A, Trichopoulos
smoking,
D, Tzonou A, Zavitsanos
coffee drinking,
and occupation
Greece, J Nat1 Cancer Inst. 1%35;75:455-61. 20. Armitage P, Berry G. Statistical Methods Blackwell
Scientific;
21.
Agency
of Carcinogenic
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CS,
for Research
on Cancer
Research.
(IARC).
Risks to Humans. Overall Evaluation
Monographs.
Targett
in Medical
E, Trichopoulos
for bladder cancer
in
2nd ed. Oxford:
1988:264.
International
Evaluation
X, Velonakis
as risk factors
suppl. 7. Lyon: IARC;
Ratten
fetal growth
GJ,
Abel1 DA,
and on maternal
IARC
Monographs
of Carcinogenicity:
on the
An Updat-
1987:272.
Beischer
estriol
NA.
excretion,
The
influence
of smoking
Aust NZ J Ostet
on
Gynaecol.
1977;17:126-30. 23.
The Health Consequences
Washington, Assistant
DC: US Government
Secretary
Human Services 24.
publication
Office on Smoking
mortality
A Report of the Surgeon General.
1980. Public Health Service, and Health.
US Department
Office of the of Health
and
o-326-0003.
Rush D, Cassano P. Relationship
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for Health,
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of cigarette
among all births in Britain,
smoking and social bias to birth weight
5-l 1 April 1970, J Epidemiol
Community
1983;37:249-55.
25. association
Marbury CM, of alcohol
Linn S, Monson consumption
R, Schoenbaum
with
outcome
S, Stubblefield
of pregnancy,
Am
GP, Ryan JK. The J Public
Health.
1983;73:1165-8. 26. maternal
Bernstein
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RH,
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levels of free estradiol in first compared to second pregnancy: Hsieh C-C,
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Higher differ-
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Tzonou A, Trichopoulos
1991;2:95-8.
Henderson
D. Birth order and breast cancer risk, Cancer
Pregnancy estrogens, coffee intake, alcohol intake, gonadal tumors, breast
cancer.
INTRODUCTION There are several reasons to examine whether coffee and alcohol intake during preg nancy affects pregnancy estrogen levels. First, there is converging evidence from several large human studies that coffee consumption, even in modest quantities, is associated with low birth weight (l-4). A similar but stronger association between tobacco smoking during pregnancy and birth weight (S-8) has been attributed (9) to tobacco effects on pregnancy estrogen levels (9, lo), raising the possibility that an analogous mechanism may be responsible for the association between maternal coffee intake and birth weight. Second, maternal alcohol intake has dose-dependent prenatal effects in both humans and experimental animals (mainly Sprague-Dawley rats) ( 1 l), but these ate neither predictable nor adequately explained, allowing speculations that invoke female reproductive hormones (not necessarily estrogens) (11). Third, pregnancy estrogens have been implicated by several authors in the etiology of a number of malignancies, including testicular cancer ( 12, 13), ovarian germ-cell tumors (14), and possibly breast cancer (15). Given the rarity of these tumors, epidemiologic assessment of the corresponding hypotheses will depend, to a considerable extent, on the identification
From the Department of Hygiene and Epidemiology, University of Athens Medical School (E. P., K. K., Y. S., K. P.) and Biomedicine Laboratories (E. S. ), Athens, Greece, and the Department of Ep~demiolo~, Harvard School of Public Health, Boston, MA (D. T.). Address reprint requests to: Dimitrios Trichopoulos, MD, Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115. Recewed December 12, 1990; revised May 21, 1991. Q 1992 Elsevier Scw~ce Putdishing Co.,
Inc.
1047~2797/92/$05.00
242
Pemdou et al. PREGNANCY ESTROGENS,
COFFEE, AND ALCOHOL
AEP Vol. 2. No. 3 Muy 1992: 241-247
of correlates or determinants of pregnancy estrogens. Coffee and alochol intake may or may not be determinants of pregnancy estrogens, but they are highly repeatable in dietary histories and, therefore, suitable factors for epidemiologic investigation. In this report we examine whether moderate coffee and alcohol intake during pregnancy affects blood levels of total estrogens (TE), estradiol (EZ), and total estriol (E3). Human placental lactogen (hPL) was also measured for exploratory purposes.
MATERIALS
AND
METHODS
During the first 6 months of 1987, 177 women were randomly chosen among those attending the outpatient maternity clinic of a major university hospital in Athens. Two groups of women were included: those who were smokers throughout their index pregnancies, and those who have never smoked regularly during their lives and not at all during these pregnancies. Once or twice per week during the study period, the same investigator (K. I’.) visited the maternity clinic and requested permission to interview and take blood samples from pregnant women attending the clinic. The objective was to have adequate numbers of women to assess the effects, if any, of tobacco smoking, coffee drinking, and alcohol intake. Since smoking during pregnancy is rare, whereas light and moderate coffee and alcohol drinking is not, all identified smokers were asked to participate, whereas only the first two or three nonsmoking women during every visit were contacted. Women with a twin pregnancy, diabetes mellitus, hypertension, thyroid disease, and chronic use of any medication for whatever reason at any time during this pregnancy were not asked to be part of the study; all study pregnancies led to normal live births. A total of 141 women agreed to participate (80%); among them, 49 were smokers and the remaining 92 never smoked regularly in their lives. Morning blood samples were taken from these women during the 26th and 31st week of their pregnancies; the 26th week was chosen because at that time, TE levels are midway through their gestational age-dependent increase. Measurements were taken during the 31st week of pregnancy in order to assess whether the patterns observed are reasonably consistent, since TE levels show little increase between the 26th and 31st weeks (16, 17). E2, E3, TE, and hPL levels were determined by radioimmunoassay. The TE assay (Radioassay Systems Laboratories, ICN Biomedicals, Carson, CA) detects the additive concentration of unconjugated estradiol-17/3 and estrone (El); it does not detect any of the estrogen sulfates and glucuronides, and does not distinguish among free El, E2, and E2 bound to circulating binding proteins. TE measurements are considered an approximation of plasma estrogenicity. The E2 assay (Leeco Diagnostics, Southfield, MI) detects total serum E2 level, the majority of which is bound to sex hormone-binding globulin. E2 is biologically the most potent among the estrogens. The E3 assay (RADIM, Pomezia, Rome, Italy) measures free estriol together with conjugates that are hydrolyzed by a mixture of enzymes (glucuronidase and sulfatase). Finally, the hPL assay (RADIM, Pomezia, Rome, Italy) measures the polypeptide hormone that has a short in piivo half-life and is more useful in serial measurements. On the basis of 15 blind duplicate measurements, the coefficients of variation of the assay procedures were calculated to be 4% for TE, 10% for E2, 3% for E3, and 8% for hPL. All measurements were performed at Biomedicine Laboratories (Athens, Greece) under the direction of one of us (E. S.) (9, 18). A detailed questionnaire was administered to each woman by one of us (K. I’.) at the time of the first blood drawing. The questionnaire covered socioeconomic, anthropometric, dietary, and medical variables, as well as details about tobacco smok-
Petridou et al. PREGNANCY ESTROGENS, COFFEE, AND ALCOHOL
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TABLE alcohol
243
1 Distribution of women by age, parity, weight at delivery, smoking status, intake, and coffee consumption during pregnancy Variable
Age (~1 5 19 20-24 25-29 2 30 Parity First pregnancy Second pregnancy Weight at delivery (kg) 1st quartile (566) 2nd quartile (67-72) 3rd quartile (73-80) 4th quartile (~81) Smoking during pregnancy (cigarettes/d) Nonsmokers I-10 Z-11 Alcohol consumption during pregnancy Nondrinkers Drmkersb Coffee consumption during pregnancy Nondrinkers 5 1 cup/d > 1 cup/d
n
W)
10
( 7.1)
51
(36.2) (31.9) (24.8)
45 35 65 75
(46.4) (53.6)
34 34
(24.8) (25.6) (24.8) (24.8)
92 29 20
(65.2) (20.6) (14.2)
89 51
(63.6) (36.4)
40 54 46
(28.6) (38.6) (32.9)
34 35
y Four women in thex third pregnancy were included among those in their second pregnancy. b Includes women drinking from 2 glasses of alcoholic beverages per week up to 2 glasses per day.
ing and drinking of coffee and alcoholic beverages. Alcohol intake was measured in glasses of alcoholic beverages; glasses of alcoholic beverages contain usually the same amount of ethanol, because beverages with a high alcohol content are drunk in smaller quantities (and glasses) (11). Coffee consumption was measured in cups per day; all but a few of the women were drinkers of Greek (Turkish) coffee, which is known to contain about half the caffeine found in regular American coffee (19). The statistical analysis was done through standard multiple regression (20). When pregnancy hormones were considered as dependent variables, natural logarithmic transformation was utilized. In this instance, anti-logs of the partial regression coefficients indicate proportional changes. Because of missing values for one or more variables, analyses were frequently based on less than 141 of the participating women but in no instance on fewer than 131 of them.
RESULTS Table 1 shows the distribution of the women by the study variables. There were no heavy drinkers of either alcoholic beverages or coffee in this group (no woman was drinking more than 5 cups of Greek coffee per day or more than 2 glasses of alcoholic beverages per day). Virtually all drinkers were wine consumers.
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TABLE 2 Multiple regression-derived” proportional changes (and 95% confidence intervals) of serum hormone levels contrasting alcohol drinkers to nondrinkers and women in three consecutive groups with increasing daily coffee intake (nondrinkers, drinkers of up to 1 cup/d, drinkers of more than 1 cup/d) Estradiol
Estriol
Total estrogens
Placental lactogen
26th week of pregnancy
Alcohol consumption
10 (-6,
Coffee consumption
P = .23 -10 (-19, P = .04
3 1st week of pregnancy Alcohol consumption Coffee consumption
29) 1)
13 (-4, 32) P = .16 -7 (-17, P = .16
3)
l(-12, 15) P = .87 l (-8, 10) 1 = .92
-9 (-17, P = .08
20 (5, 38) P = .Ol -2 (-10, 8) P = .70
13 (-5, 15) P = .18 0 (-11, 13) P = .99
17 (1, 35) P = .04
-13 (-27, P = .I1 1)
3)
-3 (-14, P = .61
9)
-3 P = -3 P =
8)
(-12, .57 (-9, .41
4)
r Controlling for maternal age, maternal weight at the corresponding week, panty. t&acco Fmokmg, and (mutually) coffee and alcohol Intake.
Table 2 examines the effects of alcohol and coffee drinking during pregnancy on E2, E3, TE, and hPL levels, controlling for maternal age, maternal weight (at the corresponding week), parity, tobacco smoking, and (mutually) alcohol and coffee intake. With respect to hPL, there is no consistent pattern of relation with either alcohol intake or coffee intake. However, there is evidence that alcohol intake is positively related to serum E2 and TE levels, whereas coffee intake appears to be negatively related to E2 levels. Table 3 summarizes the results from multiple regression modeling of birth weight on a number of known or possible predictors (maternal age, maternal weight at delivery, parity, tobacco smoking) as well as on alcohol and coffee consumption. Children born to younger and heavier women have a higher birth weight and, as expected, tobacco smoking is associated with reduced birth weight. By contrast, neither alcohol nor coffee consumption, at the ranges examined in the present study, had a significant effect on birth weight (P > .50 in both instances).
TABLE 3 Multiple regression-derived regression coefficients (b) and standard errors (SE(b)) of birth weight (in g) on maternal age, maternal weight at delivery, parity, tobacco smoking, and coffee and alcohol consumption Units or categories
Variable Age Maternal Parity
lzg weight at delivery Primiparvus:
0
Tobacco smoking
Multlparoux Nonsmoker:
I @
Alcohol
I-10 cigarettes/d: 2 11 cigarettes/J: Nondrinkers: 0
consumption
Coffee consumption
Drinkers: 1 Nondrinkers: I
>
I cup/d: I 1 cup/d: 2
0
b
SE(b)
P
- 18.7
7.6 4.0 77.1
.02 .02 .77
38.9
.03
79.0
.52
52.5
.89
9.4 22.2 -85.0 1 2 51.0 -7.1
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DISCUSSION In this study, moderate coffee consumption was not significantly associated with birth This was not unexpected. Variability of birth weight among full-term newborns is not as large as the variability of pregnancy estrogens ( 16, 17); the association between coffee intake and birth weight is relatively weak (4); and the previous studies that have demonstrated this association included several thousand subjects (l-3). Furthermore, the confidence interval derived from the present study covers the corresponding point estimates of all major studies exploring the relation between coffee intake during pregnancy and birth weight (4). The present investigation is the first to examine whether maternal coffee intake is associated with pregnancy estrogen levels. The results are not conclusive but do suggest that a negative association exists. Since estrogens are established growth factors (21) and appear to be positively related to birth weight (9), the negative association between coffee intake and pregnancy estrogen levels could provide a plausible explanation for the negative association between coffee intake and birth weight (l-4). An analogous mechanism appears to exist with respect to maternal tobacco smoking (9, 10) and may explain the apparently additive effects of maternal coffee and tobacco consumption on birth weight (4). Several mechanisms have been postulated to explain the association between maternal smoking and birth weight, mostly focusing on placental structural changes, nutritional disturbances, and possibly direct effects of smoking on the embryo (22-24). Experimental studies probing effects of coffee on reproduction and prenatal toxicity have in general been inconclusive and no specific hypothesis has been advanced to explain the negative relation between maternal coffee consumption and birth weight (4). The evidence represented in this report integrates findings concerning both tobacco and coffee effects on birth weight in the context of the well-established growthenhancing effects of estrogens (2 1). With respect to alcohol, the data pertaining to pregnancy estrogen levels and birth weight are not clear-cut. There is strong evidence that alcoholism and alcohol abuse are associated with reduced birth weight (ll), but findings concerning the effects of alcohol consumption at the low levels considered in the present study are inconclusive; indeed, intake of up to 2 drinks per day during pregnancy was positively (although not significantly) associated with birth weight in the large study of Marbury and colleagues (25) and among nonsmokers in the recent study by Brooke and coworkers (8). Therefore, the results of the present study indicating that moderate alcohol consumption during pregnancy is positively related to levels of pregnancy TE are not incompatible with the postulated role of estrogens as an important intermediate pathway linking dietary and other exogenous factors to birth weight. It should be noted that in the present study, the relations of alcohol and coffee consumption with pregnancy estrogens were in general stronger during the 26th week than during the 3 1st week of pregnancy and more pronounced with respect to E2 and TE than with respect to E3. These findings may be accounted for by the fact that coffee and alcohol consumption was ascertained at the time of the first blood drawing during the 26th week, and by the widely supported evidence that the estrogenicity of E3 is limited and its overall biologic importance questionable (16, 17). It has been hypothesized that intrauterine exposure to high levels of endogenous tumors, including estrogens may also increase the risk of some hormone-dependent testicular cancer (12, 13), ovarian germ-cell cancer (14), and breast cancer (15).
weight.
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Likely predictors of levels of pregnancy estrogens, including severe nausea during pregnancy and maternal obesity (13, 14), maternal age (18) and birth order (18, 26, 27) have been examined as possible risk factors for gonadal germ-cell tumors and breast cancer. The identification of exogenous determinants of pregnancy estrogen levels would allow generation of additional variables that could be used as exposure indicators in epidemiologic studies.
This work was supported in Athens by a grant from the Greek Ministry of Health and in Boston by a grant to Harvard University from Mr. George S. Livanos.
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