Exploratory Study of the Relationship Between Maternal Body Mass Index and Spontaneous Fetal Movements

Abstract

Maternal body mass index (BMI) has been reported to be associated with the number of fetal body movements and the duration of fetal breathing movements in hypertensive pregnant women (Brown et al., 2008). However, whether a relationship exists in pregnancies classified as overweight or normal weight but not complicated by hypertension is unknown and the focus of this study. Forty-five maternal-fetal pairs (normotensive, normal weight=15; normotensive, overweight=15; hypertensive=15) who had participated in a study of fetal behavior which included a 20 min real-time ultrasound scan observation of fetal movements were randomly selected from the laboratory archival database. Gestational age at testing ranged from 33-39 weeks [M(SD)= 36.2 (1.4) weeks]. All infants were delivered healthy at term. Video-recordings of the ultrasound scans were scored for the number of fetal body movements (interrater reliability r=.97) and the cumulative duration of breathing (interrater reliability r=.94) movements. The number of fetal body movements differed between groups, F(2,38)=3.19, p=0.05, with fetuses of overweight mothers moving less frequently than those of normal weight mothers (M=9.7 vs 15.5, respectively). Maternal BMI prior to pregnancy, r=-0.43, p<0.01, and at time of observation, r=-0.44, p<0.01, was associated with the number of fetal body movements, but not with duration of breathing movements. As BMI increased, the number of fetal body movements decreased. It was concluded that maternal BMI may affect the number of spontaneous fetal movements. A prospective study is necessary to determine whether BMI should be considered when using body movement counts to assess well-being and/or neurodevelopment.