Placental size at 19 weeks predicts offspring bone mass at birth: findings from the Southampton Women's Survey

Abstract

Objectives: In this study we investigate the relationships between placental size and neonatal bone mass and body composition, in a population-based cohort.

Study design: 914 mother-neonate pairs were included. Placental dimensions were measured via ultrasound at 19 weeks gestation. Dual X-ray absorptiometry (DXA) was performed on the neonates within the first two weeks of life.

Results: We observed positive relationships between placental volume at 19 weeks, and neonatal bone area (BA; r = 0.26, p < 0.001), bone mineral content (BMC; r = 0.25, p < 0.001) and bone mineral density (BMD; r = 0.10, p = 0.001). Thus placental volume accounted for 6.25% and 1.2% of the variation in neonatal BMC and BMD respectively at birth. These associations remained after adjustment for maternal factors previously shown to be associated with neonatal bone mineral accrual (maternal height, smoking, walking speed in late pregnancy, serum 25(OH) vitamin D and triceps skinfold thickness).

Conclusions: We found that placental volume at 19 weeks gestation was positively associated with neonatal bone size and mineral content. These relationships appeared independent of those maternal factors known to be associated with neonatal bone mass, consistent with notion that such maternal influences might act through modulation of aspects of placental function, e.g. utero-placental blood flow or maternal nutrient concentrations, rather than placental size itself. Low placental volume early in pregnancy may be a marker of a reduced postnatal skeletal size and increased risk of later fracture.

Figure 1. A 19 week ultrasound scan showing placental size measurements in the longitudinal plane.

Figure 2. Association between placental volume at 19 weeks and neonatal bone mass

Scatter-plots illustrating the relationship between placental volume, measured by ultrasound at 19 weeks, and neonatal bone mass measured by dual x-ray absorptiometry (DXA). Placental volume correlated positively with neonatal BA, BMC and aBMD (p all <0.01). For every 1 SD increase in placental volume, BA increased by 6.2cm², BMC increased by 3.6g, aBMD increased by 0.0029g/cm² and BA adjusted for crown-heel length increased by 2.9 cm².

Figure 3. Association between placental volume at 19 weeks and neonatal fat and lean mass

Scatter-plots illustrating the relationship between placental volume, measured by ultrasound at 19 weeks, and neonatal bone mass measured by dual x-ray absorptiometry (DXA). Placental volume at 19 weeks was positively associated with neonatal total lean mass (r=0.23, p<0.0001) and fat mass (r=0.23, p<0.0001). There was a different pattern with proportionate body composition. Thus, placental volume was positively related to percent fat (r=0.19, p<0.0001) but negatively to percent lean (r=−0.20, p<0.0001).