Amniotic fluid index versus single deepest vertical pocket as a screening test for preventing adverse pregnancy outcome
A Cochrane review 1 included 5 studies with a total of 3,226 women with singleton pregnancies. There were no difference between amniotic fluid index (AFI) and single deepest vertical pocket (SDP) in the prevention of poor peripartum outcomes, including admission to a neonatal intensive care unit (RR 1.04, 95% CI 0.85 to 1.26; 5 trials, n=3,226); an umbilical artery pH of less than 7.1; the presence of meconium; an Apgar score of less than 7 at five minutes; or caesarean delivery. However, with AFI significantly more cases of oligohydramnios were diagnosed (RR 2.39, 95% CI 1.73 to 3.28; I2=59%), and more women had inductions of labor (RR 1.92, 95% CI 1.50 to 2.46) and caesarean delivery for fetal distress (RR 1.46, 95% CI 1.08 to 1.96).
A multicenter randomized controlled trial 2 included 1052 pregnant women with a term singleton pregnancy. Women were assigned randomly to AFI or SDP measurement for estimation of amniotic fluid volume. Oligohydramnios was defined as AFI ≤ 5 cm or the absence of a pocket measuring at least 2 × 1 cm. The diagnosis of oligohydramnios was followed by labor induction. Postpartum admission to a neonatal intensive care unit was similar between groups (4.2% [n = 21] vs 5.0% [n = 25]; RR 0.85, 95% CI 0.48 to1.50). In the AFI group, there were more cases of oligohydramnios (9.8% [n = 49] vs 2.2% [n = 11]; RR 4.51, 95% CI 2.2 to 8.57; P < 0.01) and more cases of labor induction for oligohydramnios (12.7% [n = 33] vs 3.6% [n = 10]; RR 3.50, 95% CI 1.76 to 6.96; P < 0.01) than in the SDP group. Moreover, an abnormal cardiotocography was seen more often in the AFI group than in the SDP group (32.3% [n = 161] vs 26.2% [n = 132]; RR 1.23, 95% CI 1.02 to 1.50; P = 0.03). The other outcome measures were not significantly different between the two groups.
Comment: The quality of evidence is downgraded by imprecise results (few outcome events).
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