Second-Trimester Placental Volumes Predict Birth Weight at Term

Abstract

Objective: To test the hypothesis that second-trimester placental growth is a major determinant of size at birth in healthy, active women.

Methods: Three serial measurements of fetal morphometry and placental volume were obtained between the 14th and 26th weeks of an accurately dated singleton pregnancy in 40 subjects.

Results: Second-trimester placental volumes were variable, increasing from (mean ± standard deviation) 130 ± 35 to 248 ± 67 and 375 ± 92 cm³ at 16, 20, and 24 weeks, with an average growth rate of 31 ± 8 cm³/weeks. At delivery, fresh placental volumes and birth weights were also variable, ranging between 304-823 cm³ and 2.6-4.4 kg, respectively. Significant correlations (r > 0.79) were present between second-trimester placental volume or growth rate and placental volume at delivery and birth weight, corrected for gestational age and infant sex. However, correlations between second-trimester fetal biometry and both corrected birth weight and birth weight percentile were poor (r < 0.45).

Conclusion: Second-trimester placental volumes and growth rates are good predictors of size at birth in healthy, active women. We speculate that this technique may have real value as an early screening tool to identify cases at risk of anomalous third-trimester growth.