Table 13 Impact of amniotic fluid volume assessment for oligohydramnios and associated interventions on stillbirth and perinatal outcomes

Hofmeyr et al. 2002 [126]

Japan, USA.

Review (Cochrane). 2 studies included (N = 78 women).

Assessed the impact of improved maternal hydration (drinking 2 litres water or intravenous fluids) on amniotic fluid volume and subsequent perinatal outcomes in women with oligohydramnios and normal amniotic fluid volume.

Increased amniotic fluid volume after hydration (women with oligohydramnios): weighted mean difference (WMD) = 2.01 (95% CI: 1.43–2.60)

Increased amniotic fluid volume after hydration (women with normal amniotic fluid volume): WMD = 4.5 (95% CI: 2.92–6.08)

IV hypotonic hydration (women with olighydramnios):

increased amniotic fluid volume=WMD 2.3 (95% CI: 1.36–3.24)

Isotonic intravenous hydration: [NS]

Nabhan et al. 2008 [121]

UK, USA.

Review (Cochrane). 4 RCTs included (N = 3125 women).

Compared the predictive value of AFI (intervention) versus single-deepest vertical pocket (comparison) methods of amniotic fluid volume assessment in anticipating adverse perinatal outcomes.

Fetal acidaemia: [NS]

Presence of meconium: [NS]

Apgar < 7 at 5 min: [NS]

Caesarean section: [NS]

Diagnosis of oligohydramnios: RR[Random] = 2.33 (95% CI: 1.67–3.24)

Induction of labour: RR[Fixed] = 2.10 (95% CI: 1.60–2.76)

Caesarean for fetal distress: RR[Fixed] = 1.45 (95% CI: 1.07–1.97)

Intervention studies

Alfirevic et al. 1997 [123]

UK. Liverpool Women's Hospital.

RCT. Singleton, uncomplicated pregnancies (N = 500) with gestational age ≥ 290 days.

Compared the impact of fetal monitoring by either AFI and computerised cardiotocography (intervention), or maximum pool depth and computerised cardiotocography (controls).

PMR: 0/250 in both groups [NS]

Chauhan et al. 1995 [125]

USA.

RCT. Pregnant women 26–42 wks' gestation in early labour.

Compared impact on perinatal outcomes of AFI on admission during early labour (intervention) vs. no AFI (controls).

Caesarean section for fetal distress: RR = 1.3 (95% CI: 1.1–1.7, P = 0.02).

[29/447 vs. 14/436 in intervention vs. control groups, respectively.]

LBW, macrosomia, Apgar <7, and admissions to the neonatal intensive care unit: [NS].

Oral et al. 1999 [124]

Turkey.

RCT. Singleton, uncomplicated pregnancies (N = 101) of gestational age ≥ 290 days.

Compared the impact of either AFI and computerised cardiotocography (intervention) vs. maximal vertical pocket and computerised cardiotocography (controls). Electronic fetal heart monitoring was performed in all patients.

PMR: Maximal amniotic fluid vertical pocket appeared to be slightly better than AFI for identifying the post-term pregnancy at risk for abnormal perinatal outcome.

Observational studies

Anandakumar et al. 1993 [115]

Singapore. National University Hospital.

Prospective cohort study. High-risk pregnant women (N = 565).

To evaluate the role of the AFI, used along with NST and fetal acoustic stimulation test, when required, in prediction of adverse pregnancy outcome.

PMR: 6/25, 4 in very low AFI (<5 cm) group (3/4 had reactive NST <7 days before death, P < 0.001 after controlling for NST results).

Baron et al. 1995 [117]

USA.

Prospective cohort study. Pregnant women > 26 wks gestation who had an intrapartum AFI measurement.

Compared rates of adverse fetal and neonatal outcomes in women diagnosed with oligohydramnios via AFI (cases) vs. women with normal AFI (controls).

Meconium staining: RR = 0.67 (95% CI: 0.49–0.92) in cases vs. controls, respectively.

Variable decelerations: RR = 1.44 (95% CI: 1.12–1.87) in cases vs. controls, respectively.

C-section for fetal distress: RR = 6.83 (95% CI: 1.55–30.4). cases vs. controls, respectively.

Neonatal complications: No difference between groups.

Sensitivity and specificity of oligohydramnios diagnosis for Caesarean delivery for fetal distress: 78% and 74%, respectively.

Kreiser et al. 2001 [180]

USA.

Retrospective study. Low-risk singleton pregnancies (N = 150) > 30 wks' gestation with decreased AFI. Pregnancies (N = 57) with very low AFI (≤ 5 cm); N = 93 with borderline AFI (>5 cm but < 2.5^th percentile).

Compared the impact in pregnancies with low AFI (intervention) vs. those with borderline AFI (controls).

PMR: 0 in both groups [NS]

Locatelli et al. 2004 [116]

Italy.

Prospective study. Uncomplicated, singleton pregnant women (N = 3050) with a non-anomalous fetus reaching 40 wks' gestation recruited from 1997–2000. All women underwent semi-weekly monitoring of AFI until delivery. Oligohydramnios (N = 341).

Compared the rate of oligohydramnios in gestations with adverse perinatal outcome, including 5-min Apgar score < 7; umbilical artery pH < 7.0; Caesarean section for fetal distress; or fetal death (cases) vs. favorable outcome (controls).

Oligohydramnios: 33/167 (19.8%) vs. 308/2883 (10.7%) in cases and controls, respectively; P = 0.001).

Morris et al. 2003 [120]

UK. University teaching hospital.

Prospective, double-blind cohort study. Pregnant women (N = 1584) ≥40 wks of gestation were subjected to ultrasound assessment.

To compare predictive ability single ultrasound scan to detect a single deepest pool of AFI<2 cm (exposed) vs. AFI<5 cm (unexposed) in anticipating subsequent adverse pregnancy outcome.

PMR: 0 in both groups.

An AFI <5 cm but not a single deepest pool <2 cm was significantly associated with birth asphyxia or meconium aspiration.

Sensitivity of AFI < 5 cm for major adverse outcome: 28.6%

Myles et al. 1992 [118]

USA.

Prospective cohort study. N = 218 pregnant women on whom AFI was performed (N = 125 with greater volume in upper quadrants; N = 93 with greater volume in lower quadrants).

Assessed the predictive value of distribution of amniotic fluid measured by the 4-quadrant method, comparing perinatal outcomes among women with greater amniotic fluid volume in upper quadrants (intervention) vs. lower quadrants (comparison).

Meconium staining: 32.8% vs. 9.7% in intervention vs. comparison groups, respectively (P < 0.0001).

1-min Apgar <7: 12.0% vs. 2.2% in intervention vs. comparison groups, respectively (P < 0.007).

Umbilical arterial pH<7.20: 29.6% vs. 8.9% in intervention vs. comparison groups, respectively (P < 0.0105).

Umbilical venous pH <7.20: 8.9 vs. 0% in intervention vs. comparison groups, respectively (P < 0.0398).

Sherer et al. 1996 [181]

USA.

Retrospective database study. N = 352 nonhypertensive, nondiabetic pregnant women delivering at < 32 wks' gestation with amniotic fluid measurement performed as part of BPP <24 hours before delivery.

Assessed association of low AFI with fetal movements.

Low AFI associated with reduced fetal movements (P < 0.0001).

Higher incidence of chorioamnionitis in patients with no fetal movements (P < 0.005)

Youssef et al. 1993 [119]

Egypt.

Observational study. Fetuses (N = 174) within one wk of delivery.

Compared the impact of the single largest vertical pocket (oligohydramnios = depth < 1 cm) (study group) vs. the 4-quadrant amniotic fluid index (oligohydramnios ≤5 cm) (controls).

The AFI was more sensitive in predicting mortality (87.5%) and the following measures of perinatal morbidity: low 5-minute Apgar score (88.8%), fetal distress during labour (86.6%), meconium-stained amniotic fluid (63.6%), and the presence of fetal growth restriction (79.4%).