Relationship between placental morphological parameters and birth weight in term newborns: a birth cohort study

  Objective  To explore the effect of various morphological indexes of placenta on birth weight in full-term neonates.

  Methods  From the Ma ′anshan-Anhui Birth Cohort (MABC) – a study on eugenics in Anhui province, we consecutively recruited 3 474 women at 8 – 14 gestation weeks between May 2013 and September 2014. Information on sociodemographics and pregnancy complication at first, second, and third trimester were collected among the pregnant women; physique of the newborns and morphological parameters of placentae were measured at the deliveries of the women. Placental surface area and volume were calculated for 2 604 pregnant women with full-term singleton. Analysis of variance and chi-square test were used to describe distribution characteristics of the data collected. Logistic regression model was used to analyze the relationship between placental morphological indicators and birth weight.

  Results  The means of placenta morphological indicators were 18.95 cm for length, 16.61 cm for width, 2.35 cm for thickness, 248.67 cm² for surface area, and 390.72 cm³ for volume and all the indicators increased with the increment of newborn birth weight. After adjusting for confounding factors, the results of logistic regression indicated that smaller placenta length (odds ratio OR ＝ 2.15, 95% confidence interval 95% CI: 1.46 – 3.15), width (OR ＝ 1.71, 95% CI: 1.17 – 2.50), surface area (OR ＝ 2.94, 95% CI: 2.08 – 4.16), and volume (OR ＝ 3.84, 95% CI: 2.01 – 4.01) were risk factors of small for gestational age (SGA); while greater placenta length (OR ＝ 0.48, 95% CI: 0.25 – 0.95) and surface area (OR ＝ 0.54, 95% CI: 0.29 – 0.99) were protective factors for SGA. In contrary, greater placenta length (OR ＝ 2.23, 95% CI: 1.66 – 2.99), width (OR ＝ 1.54, 95% CI: 1.14 – 2.09), thickness (OR ＝ 2.60, 95% CI: 1.92 – 3.54), surface area (OR ＝ 3.54, 95% CI: 2.69 – 4.65), and volume (OR ＝ 4.34, 95% CI: 3.28 – 5.75) were risk factors of large for gestational age (LGA); but smaller placenta width (OR ＝ 0.38, 95% CI: 0.24 – 0.61), surface area (OR ＝ 0.43, 95% CI: 0.27 – 0.70), and volume (OR ＝ 0.48, 95% CI: 0.29 – 0.78) were protective factors of LGA. The effect of smaller placenta width on the risk of SGA, greater placenta width on the risk of LGA, and smaller placenta volume on the risk of LGA were only observed among the pregnant women giving birth to male, female, and male infants.

  Conclusion  The size of the placenta is closely related to intrauterine growth and is influenced by the sex of the fetus.