Placental weight and neurologic outcome in the infant: a review

Abstract

Objective: To review the agreement of published standards on placental weights (PW) and fetal–placental (F/P) ratios, examine factors contributing to PW and ask whether aberrant placental weight is associated with adverse neurologic outcome. Methods: We conducted a literature search for standards of PW, F/P ratio and the relationship of PW to perinatal death, neonatal encephalopathy or cerebral palsy. We reviewed 17 studies of normative PW and 10 of F/P ratios. Since 1990, seven studies compared mean and extreme percentile bounds between 35 and 42 weeks of gestation. Nine publications examined PW and neurologic outcome. Results: Untrimmed placentas were heavier by 131–193 g. F/P ratios differed by 0.2–2.34 between trimmed and untrimmed placentas. Fresh, frozen or fixed preparation prior to weighing had minimal effect on weight. Gender and race had negligible affect. Placentas from caesarean sections averaged 75 g heavier than vaginal deliveries. There were no consistent associations of aberrant PW and neurologic outcome. Conclusions: Reference standards of recent studies on trimmed placentas were largely in agreement. Current findings relating aberrant PW and adverse neurologic outcome are inconclusive. Further study of the relationship between placental weight and neonatal encephalopathy or cerebral palsy is warranted, in representative populations using within-study controls.

Keywords::

• Cerebral palsy
• fetoplacental ratio
• neonatal encephalopathy
• normative weight
• placenta
• placentomegaly

Declaration of Interest: The authors declare no conflicts of interest.