Very-early-onset discordant growth in monochorionic twin pregnancy

The significance of growth restriction in the first trimester in karyotypically normal fetuses is uncertain.

We report a case of diamniotic monochorionic twin pregnancy with marked growth discordance noted in the first trimester. No major congenital or karyotype abnormalities or ongoing evidence of twin-twin transfusion syndrome were found during gestation. Birth weight discordance in the twins was 49.5%. Histologic examination revealed immature villi, with a shortage of terminal villi and an abundance of intermediate mature villi, as well as hypoxic areas with altered villi in the part of the placenta supplying the smaller twin.

The causes underlying discordant growth in karyotypically normal twin pregnancies without evidence of twin-twin transfusion syndrome are not entirely clear. There may be other conditions responsible for discordant growth that occur in the first or early second trimester of pregnancy.