Association of placenta weight and morphology with term low birth weight: A case-control study

Few studies identified the role of the placenta in birth weight. We aimed to explore the connection between placenta weight, morphology, and term low birth weight (TLBW).

This was a case-control study of neonates born at ≥37 weeks' gestation enrolled in a general hospital from January 2018 to November 2022. Cases (<2,500 g) identified via birth certificates or medical records were matched with controls on the basis of date of birth, gestational age, sex, and maternal age. A nomogram predictive model was constructed based on logistic regression, using placenta parameters and perinatal information.

A total of 290 neonates (115 with diagnosed TLBW and 175 controls) were determined. There were no significant differences between the two groups concerning gestational age (265.5 ± 5.4 vs 266.3 ± 5.3 days, P = 0.1397), gender, and maternal age at delivery (32.0 ± 3.5 vs 32.1 ± 3.1 years, P = 0.867). The placenta weight (479.0 ± 80.1 vs 597.1 ± 83.1 cm), length (16.3 ± 2.1 vs 18.8 ± 2.0 cm), width (14.3 ± 2.1 vs 16.9 ± 2.0 cm), and thickness (2.3 ± 0.5 vs 2.4 ± 0.4 cm) in the TLBW group were much lower than those in the control group (all P < 0.001). Univariate predictors of TLBW included smaller placental weight, length, width, thickness, volume, and surface area. When put into a multivariate model, placental weight (aOR for per 10 g increase: 0.89; 95% CI: 0.84-0.94) and width (aOR for per 1 cm increase: 0.69; 95% CI: 0.54-0.88) remained to be independent predictors even after controlling for relevant confounders. The odds of TLBW increased when placental weight was below the 50th percentile (aOR: 5.08, 95% CI: 2.59-9.95). Placental width below the 50th percentile was significantly associated with an increased risk of TLBW (aOR: 6.57, 95% CI: 2.73-15.82).

Placental weight and width were found to be associated with TLBW. Further studies focusing on placental function, histology, and pathophysiology are needed to better understand the underlying mechanisms influencing fetal growth and TLBW.