Perinatal factors associated with the respiratory distress syndrome Heather Bryan, MD, Peter Hawrylyshyn, MD, Sheilah Hogg-Johnson, MMath, Susan Inwood, RN, Allen Finley, MD, Mario D'Costa, PhD, and Mary Chipman, MA Toronto, Ontario, Canada Perinatal factors related to the incidence of respiratory distress syndrome were analyzed by the multiple logistic regression statistical method in 263 mothers and their 298 offspring delivered between 24 and 35 weeks' gestation in a 1-year period in a regional referral perinatal center. The risk of respiratory distress syndrome in white infants rose with decreasing gestational age (p < 0.0001) while prolonged rupture of membranes of >24 hours in the absence of maternal infection (28% of cases) was highly protective (p < 0.0001). Compared with vaginal delivery, cesarean delivery without labor increased the risk of respiratory distress syndrome (p = 0.03). The administration of tocolytic drugs was unrelated to the incidence of respiratory distress syndrome, but corticosteroid therapy given at least 72 hours before delivery was protective (p = 0.03). Male and female infants were equally at risk for respiratory distress syndrome as were black and white infants, but other races had a lower incidence (p = 0.004). Infants with respiratory distress syndrome were on mechanical ventilators longer than those with other respiratory illnesses. (AM J OSSTET GVNECOL 1990;162:476-81.)
Key words: Respiratory distress syndrome, delivery mode, prolonged rupture of membranes, corticosteroids, tocolytics Respiratory distress syndrome (RDS) in premature infants has decreased in incidence over the years since the establishment of neonatal intensive care units. I The mortality and morbidity, however, still remain significant, particularly in very-low-birth-weight infants. 2 • 3 Obstetric management of the mother in premature labor has become increasingly important in efforts attempting to minimize or prevent the onset of RDS in the newborn infant. Stabilization of the at-risk mother with admission to the hospital, bed rest, clinical monitoring, and frequent assessment of fetal well-being are important aspects contributing to effective treatment, as well as controlled labor and atraumatic delivery.4 The indirect assessment of fetal lung maturity with measurements of amniotic fluid lecithin/sphingomyelin (LIS) ratios: the administration of steroids to the mother before delivery to accelerate fetal pulmonary development,6 and the use of tocolytic therapy to delay labor' are also measures adopted to reduce the incidence of neonatal RDS. There is still controversy, howFrom the Mount Sinai Hospital and the Departments of Pediatrics, Obstetrics and Gynaecology, Preventive Medicine, and BIOstatIStics and Clinical BiochemIStry, University of Toronto. Supported by grant MT5609, Medical Research Counczl of Canada. Presented at the Forty-Fourth Annual Meeting of The Society of Obstetriczans and Gynaecologists of Canada, Vancouver, British Columbia, june 21-25,1988. Received for publication june 29, 1989; revised july 31, 1989; accepted August 23, 1989. Reprint requests: Dr. M. Heather Bryan, Division of Neonatology, Mount Sinai Hospxtal, 600 University Ave., SUIte 1241, Toronto, Ontario, Canada M5G 1X5. 6/1/16425
476
ever, about the management of premature rupture of the membranes in preterm pregnancies, which has been reported to occur in about a third of deliveries of low-birth-weight infants." The obstetrician must decide whether the risks of infection to the mother and infant outweigh the risks of prematurity with all its associated problems. 9 We have analyzed our experience in a tertiary highrisk perinatal unit over a I-year period by examining all pregnancies where infants born alive at
Key words: Respiratory distress syndrome, delivery mode, prolonged rupture of membranes, corticosteroids, tocolytics Respiratory distress syndrome (RDS) in premature infants has decreased in incidence over the years since the establishment of neonatal intensive care units. I The mortality and morbidity, however, still remain significant, particularly in very-low-birth-weight infants. 2 • 3 Obstetric management of the mother in premature labor has become increasingly important in efforts attempting to minimize or prevent the onset of RDS in the newborn infant. Stabilization of the at-risk mother with admission to the hospital, bed rest, clinical monitoring, and frequent assessment of fetal well-being are important aspects contributing to effective treatment, as well as controlled labor and atraumatic delivery.4 The indirect assessment of fetal lung maturity with measurements of amniotic fluid lecithin/sphingomyelin (LIS) ratios: the administration of steroids to the mother before delivery to accelerate fetal pulmonary development,6 and the use of tocolytic therapy to delay labor' are also measures adopted to reduce the incidence of neonatal RDS. There is still controversy, howFrom the Mount Sinai Hospital and the Departments of Pediatrics, Obstetrics and Gynaecology, Preventive Medicine, and BIOstatIStics and Clinical BiochemIStry, University of Toronto. Supported by grant MT5609, Medical Research Counczl of Canada. Presented at the Forty-Fourth Annual Meeting of The Society of Obstetriczans and Gynaecologists of Canada, Vancouver, British Columbia, june 21-25,1988. Received for publication june 29, 1989; revised july 31, 1989; accepted August 23, 1989. Reprint requests: Dr. M. Heather Bryan, Division of Neonatology, Mount Sinai Hospxtal, 600 University Ave., SUIte 1241, Toronto, Ontario, Canada M5G 1X5. 6/1/16425
476
ever, about the management of premature rupture of the membranes in preterm pregnancies, which has been reported to occur in about a third of deliveries of low-birth-weight infants." The obstetrician must decide whether the risks of infection to the mother and infant outweigh the risks of prematurity with all its associated problems. 9 We have analyzed our experience in a tertiary highrisk perinatal unit over a I-year period by examining all pregnancies where infants born alive at
