Is polyhydramnios in an ultrasonographically normal fetus an indication for genetic evaluation?

OBJECTIVE

Our purpose was to determine the frequency of fetal chromosomal anomalies in pregnancies complicated by polyhydramnios.

STUDY

DESIGN

Between Jan. 1, 1992, and July 31, 1993, an amniotic fluid index was measured prospectively in 2730 third-trimester pregnant women. Polyhydramnios was defined as an amniotic fluid index > or = 24 cm. A computer search identified all infants born with structural or chromosomal anomalies.

RESULTS

Polyhydramnios was detected in 49 of 2730 women (1.7%). The incidence of chromosomal anomalies was two in 49 (4.1%) compared with three in 2681 (0.12%) among women with normal fluid (p < 0.05). Six of the 49 newborns had structural anomalies (12.2%), whereas 48 of 2681 (1.8%) structural anomalies occurred in the control group (p < 0.05). Among study patients both fetuses with chromosomal anomalies were growth retarded; four of the six structural anomalies were associated with an amniotic fluid index > 30 cm.

CONCLUSIONS

(1) Polyhydramnios is associated with an increased incidence of congenital fetal anomalies. (2) Growth-retarded fetuses with polyhydramnios warrant genetic evaluation. (3) A genetic study is not absolutely indicated for patients with polyhydramnios and a sonographically normal fetus.