B ackground: Preterm birth which is defined as delivery before 37 completed weeks was implicated in approximately two thirds of neonatal death. Also preterm labors are the most common cause of mortality and morbidity of infants in recent years and it costs high prices for health system. We evaluate the relationship between prepregnancy maternal body mass Index (BMI) and spontaneous and indicated preterm birth.
Methods: This study included 250 healthy pregnant women, without any risk factors of preterm birth, were classified into categories that were based on their body mass index. Association between BMI, weight gain and rout of delivery were examined. Rates of indicated and spontaneous preterm birth were compared.
Results: Obese women delivered at a more advanced gestational age. (38/34±1/66 weeks vs 37/61±2/44, p=0/006). Obese patients had significantly lower incidence of spontaneous preterm birth at < 37 weeks of gestation (16/8% vs 31/2% p=0/008). Obese women had larger infants (3354/95±596/75 vs 311.24±558/357 p=0/001), and had more frequent cesarean delivery (69/6% vs 52/8%, p=0/006). Weight gain during pregnancy is poorly correlated with prepregnancy BMI (14/41±7/93 kg vs 13/78±4/94kg, p=0/4) and preterm birth.
Conclusion: In this survey, there was adverse correlation between body mass index (BMI) before pregnancy and preterm labor less than 37 completed weeks and we suggest more study for evaluation between spontaneous and induced preterm labor mechanism and in obese and non obese women. However according to this survey obesity before pregnancy is associated with a lower rate of spontaneous preterm birth.