Maximal amniotic fluid index as a prognostic factor in pregnancies complicated by polyhydramnios.

OBJECTIVES: Polyhydramnios is present in approximately 2% of pregnancies and has been associated with a variety of adverse pregnancy outcomes. Our aim was to evaluate the association between the maximal amniotic fluid index (AFI) and the frequency of specific adverse outcomes.

METHODS: This was a retrospective chart review of 524 singleton pregnancies diagnosed with polyhydramnios and delivered in a single tertiary referral center between 2003 and 2008. Polyhydramnios was defined as either AFI ≥ 25 cm or a maximum vertical pocket (MVP) ≥ 8 cm even in the presence of AFI < 25 cm. The cohort was stratified into four groups based on the maximal AFI noted during the pregnancy: < 25 cm but with MVP ≥ 8 cm; 25-29.9 cm; 30-34.9 cm; and ≥ 35 cm. Data were collected to determine the frequency of the following adverse pregnancy outcomes: prenatally diagnosed congenital anomalies, fetal aneuploidy, preterm delivery, Cesarean delivery, low birth weight, 5-min Apgar score < 7 and perinatal mortality.

RESULTS: Higher AFI was associated with a statistically significant increase in the frequency of adverse pregnancy outcomes. The most severe form of polyhydramnios, as based on the maximal AFI (≥ 35 cm; n = 67), was associated with the highest rates of prenatally diagnosed congenital anomalies (79%), preterm delivery (46%), small-for-gestational-age neonate (16%), aneuploidy (13%) and perinatal mortality (27%). No significant association between degree of polyhydramnios and adverse outcome was demonstrated in cases of idiopathic polyhydramnios (n = 253).

CONCLUSIONS: There is an association between the frequencies of a variety of adverse pregnancy outcomes and the severity of polyhydramnios as reflected by the maximal AFI.