Low placental weight and risk for fetal distress at birth

Abstract Objective: The objective of this study was to assess whether low placental weight is associated with higher risk of emergency delivery (cesarean section and vacuum-assisted delivery).

This was a retrospective cohort study, including 657 normally developed term pregnancies. A strict methodology was used to provide reliable and reproducible placental weight measurement. Fetal heart rate patterns were analyzed according to the guidelines of the Royal College of Obstetricians and Gynecologists. Linear and logistic multiple regression analyses were used to assess risk factors for emergency delivery.

Nulliparity, placental weight <10th percentile, and delivery after 40 weeks of gestation remain significantly associated with higher risk of emergency delivery for non-reassuring fetal status in the multivariable model [odds ratio (OR) 5.13, 95% confidence interval (CI) 2.85-9.22, P<0.001; OR 2.46, 95% CI 1.49-4.06, P<0.001; OR 2.23, 95% CI 1.26-4.51, P=0.01, respectively]. In the group of women who had an emergency delivery, 17.3% had a placental weight <10th percentile, which was significantly different to the group of women who delivered normally (9.4%, P≤0.04). If only emergency cesarean sections were analyzed, the percentage of women with placental weight <10th percentile was 37.5% in the cesarean section group compared to 9.8% in women who delivered normally (P≤0.001).

This study suggests that, in clinically normally developed term pregnancies, placental weight <10th percentile is associated with an increased risk for emergency delivery during labor. These results warrant further prospective studies for potential use in clinical practice.