Perinatal morbidity and placental size in gestational impaired glucose tolerance

The clinical significance of large placentas in diabetic pregnancies is not known. A retrospective study was performed to determine whether a disproportionately large placenta, as represented by a high ratio of placental weight to birth weight (placental ratio), in pregnancies complicated by the World Health Organization category of impaired glucose tolerance (IGT), was associated with perinatal morbidity.

We categorized 1472 consecutive singleton pregnancies with gestational IGT as having a high placental ratio (> 0.2095 or mean plus one standard deviation of the value established for appropriate-for-gestational age infants from nondiabetic pregnancies in a previous study) or a normal ratio. Maternal characteristics and glycemic parameters, infant birth weight and neonatal complications, and placental weight were compared between these two groups.

A high placental ratio was found in 400 (27.2%) pregnancies. This group had similar maternal anthropometric and glycemic parameters, except for a slightly higher prepregnancy body mass index and fasting glucose level in the oral glucose tolerance test. The high placental ratio was from increased placental weight rather than the decreased birth weight. The neonates had increased incidence of low 1-minute Apgar score, treatment for neonatal jaundice and infection, and respiratory complications. After adjusting for the effects of preterm birth and vaginal delivery, a high ratio was still associated with low Apgar score, respiratory complications, and treatment for infection.

The placental ratio in pregnancies complicated by IGT was unrelated to maternal characteristics or glycemic status, but a high ratio was associated with increased perinatal morbidity.