Analysis of placental weight centiles is useful to estimate cause of fetal growth restriction.

To establish a nomogram of placental weight at delivery and to clarify the associations among standardized placental weights and known risk factors of fetal growth restriction (FGR). Consequent cases who delivered singleton babies after 22 weeks of gestation at our hospital between 2005 and 2009 were retrospectively analyzed using the hospital database. The data of neonatal birth weight, placental weight, maternal demographics and variables associated with FGR were collected. From these data, we established the nomogram of neonatal and placental weight, and fetal:placental weight ratio against gestational age at the delivery. According to regression formula, the z-score of the neonatal and placental weights were calculated, and the relation between the standardized placental weights and risk factors associated with growth restriction were analyzed. Nomograms of neonatal and placental weight, and fetal:placental weight ratio were demonstrated using 3434 cases. Z-scores of placental weights were low in cases with low maternal body mass index, preeclampsia, abnormal placental forms and short umbilical cord. They were also low in cases with 'placental dysfunction', which we usually defined when any other known risk factor was not seen in FGR cases. A standard curve of placental weight would be a useful tool to explain a certain degree of placental development and the cause of FGR, and to use for further research.