THE EXENCEPHALY-ANENCEPHALY SEQUENCE - ULTRASONIC EVALUATION IN EARLY-PREGNANCY

Aim In animal studies exencephaly is well described as a precursor of anencephaly. We have evidence that also in the human fetus the transition from exencephaly to anencephaly is possible. Method We diagnosed either exencephaly or anencephaly by high-frequency vaginal ultrasound in 14 human fetuses at gestational ages varying between 9 + 4 and 22 + 3 weeks. Results In the first trimester exencephaly was the predominant finding, while in the second trimester the classic appearance of anencephaly was seen more often. In one fetus with exencephaly diagnosed at a gestational age of 12 + 2 weeks, where the parents decided not to intervene, the transition to anencephaly was documented by serial ultrasound examinations. Conclusions Our findings support an exencephaly-anencephaly sequence also in humans. The cephalic changes resulting in the classic anencephalic appearance are of importance for the first trimester diagnosis with high resolution vaginal probe ultrasound.