Fetal breathing movements before oxytocin induction in prolonged pregnancies Peter Schreyer, MD, Naomi Bar-Natan, MD, Dan J- Sherman, MD, Shlomo Arieli, MD, and Eliahu Caspi, MD Zerifin, Israel Fetal breathing movements were recorded before elective labor induction in 65 patients with uncomplicated prolonged pregnancies. Breathing activity was observed in 41 patients and was absent in 24. Comparison of these two groups indicated that the induction period was significantly shorter and the oxytocin requirement significantly lower in the group with no fetal breathing movements (mean, 319.3 vs 648.5 minutes and 1133.7 vs 2708.4 mlU, respectively). These findings remained valid regardless of Bishop scores. The data suggest that fetal breathing movements are predictive of the effectiveness of oxytocin induction in prolonged pregnancies. (AM J OSSTET GVNECOL 1991;165:577-81.)
Key words: Fetal breathing movements, labor induction, prolonged pregnancy The optimal management of postterm pregnancy is as yet unestablished, and probably no obstetric disorder is surrounded by more confusion that postdatism. Physiological placental aging causes progressive utero placental insufficiency, which in turn leads to increased rates of fetal asphyxia, oligohydramnios, and in severe cases, nervous system damage and death.! The decreased placental blood flow in postdate pregnancies represents a continuum that may in fact begin before 42 weeks' gestation. Studies suggest that perinatal morbidity increases after 40 weeks' gestation. 2 , 3 In uncomplicated, well-established, postterm pregnancies, induction of labor is generally recommended if the cervical score is favorable; however, the proper procedure in cases of unripe cervix remains controversial. 4,5 Fetal breathing movements are an integral part of normal physiological development, beginning early in gestation. Significant increase of the incidence of fetal breathing movements by maternal injection of glucose in term pregnancies was previously reported." Studies have shown that fetal breathing activity gradually begins to diminish at 72 hours before labor and ceases completely during the active phase of labor.7-9 The increase in the level of prostaglandins during labor may exert a dual and simultaneous influence, activating myometrial contractility!O and inhibiting the fetal respiratory center. II. !2 Decreased fetal breathing movements have been shown to be a sensitive parameter in From the Department of Obstetrics and Gynecology, Assaf Harofe Medical Center; affiliated with Sack/er School of Medicine. Tel Aviv University. Received for publication October 15, 1990; revised February 12, 1991; accepted February 27, 1991. Reprint requests: Peter Schreyer, MD, Department of Obstetrics and Gynecology, Assaf Harofe Medical Center, Zerifin 70300, Ismel.
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distinguishing between true and false premature labor!3-!5 and in the diagnosis of true term labor.!6 The aim of this study was to investigate fetal breathing movements as a possible parameter for the prediction of the effectiveness of oxytocin induction in postdate pregnancies.
Patients and methods The study group consisted of 65 patients at gestational age 287 to 294 days who underwent fetal testing before the induction of labor at the Assaf Harofe Medical Center between June 1, 1988, and June 1, 1989. To assure the accurate assignment of gestational age, the study patients were required to meet the following criteria: a reliable last menstrual period (known date); a history of regular menstrual cycles; and one firsttrimester or two second-trimester ultrasonographic examinations confirming the menstrual age. Patients with pregnancy-induced hypertension, diabetes mellitus, previous cesarean section, intrauterine growth retardation, approximate fetal weight >4300 gm, or malpresentation were excluded from the study. Patients did not take any medication except iron or vitamin supplementation for at least 2 weeks before admission, fasted for at least 8 hours, and did not smoke during the study. All studies began between 8 and 9 AM when an intravenous infusion of 500 ml 10% glucose was started and administered over a I-hour period. Nonstress tests were carried out throughout the infusion. Those with reactive NST results were examined for fetal breathing movements within 10 minutes from completion of the glucose infusion, using real-time ultrasonography. Fetal breathing was considered to be present when it was sustained 2:20 seconds, and absent when no sustained movement could be detected within a 45-minute pe577
578
Schreyer et al.
September 1991 Am J Obstet Gynecol
Table I. Characteristics of patient population Patient data
FBM +
FBM -
No. of patients 41 24 27.2 ± 2.4 26.6 + 2.6 Age (yr) (mean ± SEM) 7117 12 / 29 Primipara I multipara Gestational age 292.2 ± 2.1 290.1 + 1.9 (days) 28113 10114 Bishop score 3-6 / >6
Ip Value* NS NS NS 70%) showed fetal breathing movements and 10 did not. Comparison of these subgroups indicated a significantly longer mean induction time (785.2 vs 369.0 minutes) and a significantly higher mean total oxytocin requirement (3348.4 vs 1418.0 mIU) for the patients with fetal breathing movements (Table IV). Of the 27 patients with high Bishop scores, 13 showed fetal breathing movement and 14 did not. The former subgroup required a significantly longer induction period (396.1 vs 283 .9 minutes) and significantly more oxytocin to induce labor (1526.9 vs 930.7 mIU) than the patients without fetal breathing movements (Table V). Patients with low Bishop scores and no fetal breathing movements reached the end of the first stage of labor after a mean period of 6 hours and 10 minutes of oxytocin infusion, compared with 6 hours and 40 minutes in patients with high Bishop scores and fetal breathing activity. The mean oxytocin requirement was similar in both groups (3.8 and 3.9 mIU I minute). Comment
Although earlier studies have reported an approximate twofold increase in neonatal mortality associated with postdatism,18 more recent data suggest that the risk is not clearly increased. 19 The improved outcomes seem to be a result of closer fetal surveillance in postterm pregnancies. In a review of antepartum testing in
Fetal breathing activity and postterm induction
Volume 165 Number 3
579
Table II. Mode of delivery and neonatal outcome of total patient population
Mode of delivery Spontaneous Cesarean section Instrumental Fetal outcome Weight (gm, mean ± SEM) Apgar score 4000 gm)
FBM+ (N = 41)
FBM- (N = 24)
n
%
n
%
p Value*
32 4 5
78.0 9.7 12.2
22 0 2
91.6 0 8.3
NS NS NS
3608.3 ± 671.2 1 2.4 6 14.6
3718.6 0 4
+ 710.1 0 16.6
NS NS NS
Abbreviations same as in Table I. *The two-tailed Student t test for independent samples.
Table III. Length of induction and oxytocin requirement in patients with and without fetal breathing movements FBM+ (n = 34)
Induction period (minutes): Time to 3 contractions 11 0 minutes Latent phase Active phase Total induction time Oxytocin requirement (mIU) Oxytocin to 3 contractions 11 0 minutes Latent phase Active phase Total oxytocin administered
FBM- (n = 27)
129.6 356.2 167.2 648.5
± ± ± ±
90.8 253.2 89.5 354.0
72.2 167.3 79.8 319.3
478.9 1546.3 683.2 2708.4
± ± ± ±
411.1 1368.6 344.9 1727.5
221.6 632.1 280.0 1133.7
± 47.1 ± 88.2
± 39.6
± 137.0 ± 163.0 ± 518.1
± 251.7
± 709.1
p
Value*
Key words: Fetal breathing movements, labor induction, prolonged pregnancy The optimal management of postterm pregnancy is as yet unestablished, and probably no obstetric disorder is surrounded by more confusion that postdatism. Physiological placental aging causes progressive utero placental insufficiency, which in turn leads to increased rates of fetal asphyxia, oligohydramnios, and in severe cases, nervous system damage and death.! The decreased placental blood flow in postdate pregnancies represents a continuum that may in fact begin before 42 weeks' gestation. Studies suggest that perinatal morbidity increases after 40 weeks' gestation. 2 , 3 In uncomplicated, well-established, postterm pregnancies, induction of labor is generally recommended if the cervical score is favorable; however, the proper procedure in cases of unripe cervix remains controversial. 4,5 Fetal breathing movements are an integral part of normal physiological development, beginning early in gestation. Significant increase of the incidence of fetal breathing movements by maternal injection of glucose in term pregnancies was previously reported." Studies have shown that fetal breathing activity gradually begins to diminish at 72 hours before labor and ceases completely during the active phase of labor.7-9 The increase in the level of prostaglandins during labor may exert a dual and simultaneous influence, activating myometrial contractility!O and inhibiting the fetal respiratory center. II. !2 Decreased fetal breathing movements have been shown to be a sensitive parameter in From the Department of Obstetrics and Gynecology, Assaf Harofe Medical Center; affiliated with Sack/er School of Medicine. Tel Aviv University. Received for publication October 15, 1990; revised February 12, 1991; accepted February 27, 1991. Reprint requests: Peter Schreyer, MD, Department of Obstetrics and Gynecology, Assaf Harofe Medical Center, Zerifin 70300, Ismel.
6/1/29146
distinguishing between true and false premature labor!3-!5 and in the diagnosis of true term labor.!6 The aim of this study was to investigate fetal breathing movements as a possible parameter for the prediction of the effectiveness of oxytocin induction in postdate pregnancies.
Patients and methods The study group consisted of 65 patients at gestational age 287 to 294 days who underwent fetal testing before the induction of labor at the Assaf Harofe Medical Center between June 1, 1988, and June 1, 1989. To assure the accurate assignment of gestational age, the study patients were required to meet the following criteria: a reliable last menstrual period (known date); a history of regular menstrual cycles; and one firsttrimester or two second-trimester ultrasonographic examinations confirming the menstrual age. Patients with pregnancy-induced hypertension, diabetes mellitus, previous cesarean section, intrauterine growth retardation, approximate fetal weight >4300 gm, or malpresentation were excluded from the study. Patients did not take any medication except iron or vitamin supplementation for at least 2 weeks before admission, fasted for at least 8 hours, and did not smoke during the study. All studies began between 8 and 9 AM when an intravenous infusion of 500 ml 10% glucose was started and administered over a I-hour period. Nonstress tests were carried out throughout the infusion. Those with reactive NST results were examined for fetal breathing movements within 10 minutes from completion of the glucose infusion, using real-time ultrasonography. Fetal breathing was considered to be present when it was sustained 2:20 seconds, and absent when no sustained movement could be detected within a 45-minute pe577
578
Schreyer et al.
September 1991 Am J Obstet Gynecol
Table I. Characteristics of patient population Patient data
FBM +
FBM -
No. of patients 41 24 27.2 ± 2.4 26.6 + 2.6 Age (yr) (mean ± SEM) 7117 12 / 29 Primipara I multipara Gestational age 292.2 ± 2.1 290.1 + 1.9 (days) 28113 10114 Bishop score 3-6 / >6
Ip Value* NS NS NS 70%) showed fetal breathing movements and 10 did not. Comparison of these subgroups indicated a significantly longer mean induction time (785.2 vs 369.0 minutes) and a significantly higher mean total oxytocin requirement (3348.4 vs 1418.0 mIU) for the patients with fetal breathing movements (Table IV). Of the 27 patients with high Bishop scores, 13 showed fetal breathing movement and 14 did not. The former subgroup required a significantly longer induction period (396.1 vs 283 .9 minutes) and significantly more oxytocin to induce labor (1526.9 vs 930.7 mIU) than the patients without fetal breathing movements (Table V). Patients with low Bishop scores and no fetal breathing movements reached the end of the first stage of labor after a mean period of 6 hours and 10 minutes of oxytocin infusion, compared with 6 hours and 40 minutes in patients with high Bishop scores and fetal breathing activity. The mean oxytocin requirement was similar in both groups (3.8 and 3.9 mIU I minute). Comment
Although earlier studies have reported an approximate twofold increase in neonatal mortality associated with postdatism,18 more recent data suggest that the risk is not clearly increased. 19 The improved outcomes seem to be a result of closer fetal surveillance in postterm pregnancies. In a review of antepartum testing in
Fetal breathing activity and postterm induction
Volume 165 Number 3
579
Table II. Mode of delivery and neonatal outcome of total patient population
Mode of delivery Spontaneous Cesarean section Instrumental Fetal outcome Weight (gm, mean ± SEM) Apgar score 4000 gm)
FBM+ (N = 41)
FBM- (N = 24)
n
%
n
%
p Value*
32 4 5
78.0 9.7 12.2
22 0 2
91.6 0 8.3
NS NS NS
3608.3 ± 671.2 1 2.4 6 14.6
3718.6 0 4
+ 710.1 0 16.6
NS NS NS
Abbreviations same as in Table I. *The two-tailed Student t test for independent samples.
Table III. Length of induction and oxytocin requirement in patients with and without fetal breathing movements FBM+ (n = 34)
Induction period (minutes): Time to 3 contractions 11 0 minutes Latent phase Active phase Total induction time Oxytocin requirement (mIU) Oxytocin to 3 contractions 11 0 minutes Latent phase Active phase Total oxytocin administered
FBM- (n = 27)
129.6 356.2 167.2 648.5
± ± ± ±
90.8 253.2 89.5 354.0
72.2 167.3 79.8 319.3
478.9 1546.3 683.2 2708.4
± ± ± ±
411.1 1368.6 344.9 1727.5
221.6 632.1 280.0 1133.7
± 47.1 ± 88.2
± 39.6
± 137.0 ± 163.0 ± 518.1
± 251.7
± 709.1
p
Value*
