Gestational age-specific reference values of placental morphological parameters for singleton deliveries in the Chinese population

BACKGROUND: Placental morphological parameters, especially placental weight, umbilical cord length, cord coiling index and fetal-placental weight ratio (F/P ratio), are crude correlates for assessing placental function, fetal growth and development, and perinatal outcomes. METHOD: Singleton placentas from neonates delivered at a women's hospital over a period of three years were collected in a phased and continuous manner. Placental weight, umbilical cord length (UCL), umbilical coiling index (UCI), and F/P ratio were recorded for each placenta using a standardized method. RESULTS: 9385 singleton placentas from 4956 male and 4429 female neonates were included, with 68.4% (6418/9385) being delivered between 38 and 40 weeks of gestations. The mean placental weight, and F/P ratio increased gradually with gestational age, with a slight decline in the placental weight after the 40th week. The UCL increased gradually during the early gestation and remained relatively stable after 31 weeks. The UCI showed no obvious trend with mean values ranging from 0.133 to 0.217. The male infants exhibited higher mean placental weight, F/P ratio, and UCL, while female infants had a higher UCI compared to their male counterparts. On breaking down by gestational age, the differences between the male and female populations were statistically significant only in certain gestational groups for each parameter (e.g., 30, 38-40 gestational weeks for placental weights). CONCLUSION: This large study generated percentile charts for placental weight, UCL, UCI and F/P ratio in the Chinese population. This data will provide a valuable resource for Chinese physicians and may serve as a reference for other populations.