Sonography of placental abnormalities and oligohydramnios in women with elevated alpha-fetoprotein levels: comparison with control subjects.

To evaluate the relationship of placental and amniotic fluid findings to elevated maternal serum alpha-fetoprotein (MS-AFP) levels, we compared sonograms made between 18 and 24 weeks gestational age in 76 women with elevated MS-AFP levels with sonograms of a control group. Patients with fetal malformations, incorrect dates, twins, or lack of follow-up were excluded. Overall, 27 (36%) of 76 patients with elevated MS-AFP levels had placental or amniotic fluid abnormalities compared with only three (3%) of 87 control subjects. Significant differences (p less than .01) were noted in the frequency of periplacental hemorrhage (9% vs 0%), intraplacental sonolucencies greater than or equal to 1.5 cm in diameter (18% vs 3%) and moderate or severe oligohydramnios (17% vs 0%). More patients with elevated MS-AFP levels had placenta previa (4%) or placental thickness greater than or equal to 3.5 cm (12%) than did those in the control group (1% and 5%, respectively), although these differences did not reach statistical significance. Seven (26%) of the 27 patients had more than one abnormality. We conclude that placental and/or amniotic fluid abnormalities are frequently shown on sonograms in women who are examined because of elevated MS-AFP levels.