Developmental trajectories of general and breathing movements in fetal twins.

This study examined the developmental trajectories of general and breathing movements in fetal twins. Fetal movement patterns were assessed from real-time ultrasound recordings performed at 12-15, 20-23, and 28-32 weeks of gestation in 42 twin pairs. Results indicated that both general movements and breathing movements followed a curvilinear, inverted U-shaped curve. Developmental trajectories were unrelated within pairs of twins and were not associated with gestational age at birth and birth weight. However, sex differences were found for general movements with males displaying more time making general movements at 21 weeks and a steeper decline in time spent making general movements during the second half of pregnancy than females. These age-related changes in fetal movements may reflect CNS development. These findings also suggest that twins' behavioral development is largely independent of co-twin development, gestational age at birth, and birth weight, but not of fetal sex.