Placental size and large-for-gestational-age infants in women with abnormal glucose tolerance in pregnancy

Aims To determine if the placental size is disproportionately increased in the large-for-gestational age infants in pregnancies complicated by impaired glucose tolerance. Methods A retrospective study was performed on 568 consecutive singleton pregnancies complicated by gestational impaired glucose tolerance controlled with diet and who delivered within a 15-month period. The cases were categorized by the infant birthweight percentile into three groups, i.e. small-for-gestational age (< 10th percentile), appropriate-for-gestational age (10th to 90th percentile) and large-for-gestational age (> 90th percentile). Maternal and infant anthropometric data, glycaemic status, and placental weight-to-birthweight ratio were compared among the three groups. Results The infant body mass index and placental weighs showed a significantly increasing trend from the small-for-gestational age to the large-for-gestational age groups, bur there was no significant difference in the placental weight-to-birthweight ratio, values of the oral glucose tolerance test, or haemoglobin A(1c) among the three groups. On the other hand, the maternal body mass index before pregnancy and at delivery were significantly higher ill the large-for-gestational age group. The placental weight, bur not the ratio, was significantly correlated with the maternal body mass index before pregnancy and at delivery (P < 0.001). Conclusions The results indicate that the placenta is not disproportionately bigger, and therefore unlikely to be the cause, in large-for-gestational age infants. Maternal size appeared to be the major determinant of birthweight percentile ranking in pregnancies with gestational impaired glucose tolerance.