Prognostic significance of raised serum alpha-fetoprotein levels in twin pregnancies.

Maternal serum alpha-fetoprotein (AFP) was measured during the second trimester in 219 twin pregnancies uncomplicated by neural-tube defects (NTD) and in 11 twin pregnancies discordant for NTD. Serum AFP levels were recorded in multiples of the median value (MOM) calculated from normal singleton pregnancies. Of the twin pregnancies uncomplicated by NTD 49% had AFP levels less than 2.5 MOM, 7.8% had levels greater than 5 MOM and 59% of these were associated with either abortion, stillbirth or fetus papyraceous. In twin pregnancies with serum AFP levels less than 5 MOM and unsuccessful outcome was noted in only 4% (chi 2, P less than 0.05). There was a significant negative correlation between serum AFP levels and combined birthweights (r = 0.954). All 11 pregnancies discordant for NTD had serum AFP values greater than 5 MOM and this level appears to be a suitable cut-off point above which there should be further diagnostic investigations and monitoring of fetal well-being.