Intrauterine breathing movements and fetal presentation.

Fetal breathing movements in 14 twin pregnancies were examined with ultrasonic technique. The twin fetuses I in cephalic presentation showed a significantly higher percentage of apnea and periodic breathing compared with twin fetuses II. No such difference was found in twin pairs with Twin ti in breech presentation. Also in the control group of 27 singleton pregnancies, the fetuses in cephalic presentation had a higher incidence of apnea and periodic breathing than those in breech presentation. The position of the fetus seems to be decisive for the character of the breathing movements before birth.