Placental thickness on ultrasound and neonatal birthweight

Objective: To investigate the relationship between maximal placental thickness during routine anatomy scan and birthweight at delivery. Methods: This retrospective descriptive study analyzed 200 term, singleton deliveries in 2016 at Penn State Hershey Medical Center. We measured maximal placental thickness in the sagittal plane from the ultrasound images of the placenta obtained at the 18-21-week fetal anatomy screen. The relationship between placental thickness and neonatal birthweight was assessed using Pearson's correlation coefficient (r) with 95% confidence interval (CI). Logistic regression was used to assess the association between placental thickness and secondary binary outcomes of neonatal intensive care unit (NICU) admission and poor Apgar scores. Two-sample t-tests, or exact Wilcoxon rank-sum test for non-normally distributed data, were used to assess for differences attributable to medical comorbidities (pre-gestational diabetes, gestational diabetes, chronic hypertension, gestational hypertension, preeclampsia and eclampsia). Results: Placental thickness had a positive correlation with neonatal birthweight [r = 0.18, 95% CI = (0.05, 0.32)]. The mean placental thickness measured 34.2 +/- 9.7 mm. The strength of the correlation remained similar when adjusting for gestational age (r = 0.20) or excluding medical comorbidities (r = 0.19). There was no association between placental thickness and NICU admission, Apgar scores <7 or medical comorbidities. Conclusion: Our study demonstrated a positive correlation between sonographic placental thickness and birthweight. Future prospective studies are warranted in order to further investigate whether a clinically significant correlation exists while adjusting for more covariates.