Diagnosis and position shift of the first and second fetus in twin pregnancy / 대한산부인과학회잡지

Correct discrimination of the first and the second twin is important. Case: (1) The first fetus, whose amnionic cavity was closest to the cervix at 19 weeks, even though its body was higher than the second fetus, was found to be closer to the cervix by 23 gestational weeks than its twin. (2) The result of the chromosomal study of dichorionic twins at 17 gestational weeks was male with 9 inversion of the presumed first, and female with trisomy 21 of the presumed second. AT 19 gestational weeks, the sex and order of the two were found to be reversed at sonography for selective termination. In diamnionic twins, the fetus in the amnionic sac closest to the cervix is nominated as the first.