Simultaneous recording of fetal breathing movements and body movements in twin pregnancy.

Fetal breathing and body movements were simultaneously evaluated in twin pregnancies in order to determine to what extent these activities occur in a synchroneous pattern in both twin fetuses and if fetal position, presentation or sex have an influence on their behavior. Thirty healthy pairs of twins at 34-37 weeks of gestation were studied. Twenty-six percent of fetal body movements and 49% of breathing movements occurred simultaneously in both fetuses. The overall total simultaneous fetal activity rate was 53.3%. The length of breathing movements and total activity (summation of breathing and body movements) of the fetuses positioned on the right side of the uterus were significantly longer than in fetuses positioned on the left side of the uterus (p = 0.002) and (p less than 0.0001) respectively. This was also true for subgroups where only fetuses in the same presentation or of the same sex were compared. It is concluded that the fetus positioned on the right side of the uterus is more active and that fetal sex or presentation had no significant effect on intrauterine fetal activity in twin pregnancies.