When diminished amnionic luid is first identiied before the mid-second trimester, particularly before 20 to 22 weeks, pulmonary hypoplasia is a signiicant concern. he underlying etiology is a major factor in the prognosis for such pregnancies. Severe oligohydramnios secondary to a renal abnormality generally has a lethal prognosis. If a placental hematoma or chronic abruption is severe enough to result in oligohydramnios-the chronic abruption-oligohydramnios sequence (CAOS)-it commonly also causes growth restriction (Chap. 41, p. 768). he prognosis for this constellation is similarly poor. Oligohydramnios that results from membrane rupture in the second trimester is reviewed in Chapter 42 (p. 821).
Initially, an evaluation for fetal anomalies and growth is essential. In a pregnancy complicated by oligohydramnios and fetal-growth restriction, close fetal surveillance is important because of associated morbidity and mortality (Chap. 44, p. 855). Oligohydramnios detected before 36 weeks' gestation in the presence of normal fetal anatomy and growth is generally managed expectantly in conjunction with enhanced fetal surveillance. However, evidence of fetal or maternal compromise will override potential complications from preterm delivery. Antepartum management of oligohydramnios may include maternal hydration. In a recent review of 16 trials of pregnancies with apparent isolated oligohydramnios, oral or intravenous hydration was associated with significant improvement in the AFI. However, it was not clear whether this translated into better pregnancy outcomes (Gizzo, 2015).
Amnioinfusion, discussed in Chapter 24 (p. 475), may be used intrapartum to help resolve variable fetal heart rate decelerations. It is not considered treatment for oligohydramnios per se, although the decelerations are presumed secondary to umbilical cord compression resulting from lack of amnionic luid. Amnioinfusion is not the standard of care for other etiologies of oligohydramnios and is not generally recommended.
he term borderline AFI or borderline oligohydramnios is somewhat controversial. It usually refers to an AFI between 5 and 8 em (Magann, 2011; Petrozella, 2011). Through the mid-third trimester, an AFI value of 8 em is below the 5th percentile on the Moore nomogram (see Fig. 11-1). Petrozella and colleagues (2011) found that pregnancies between 24 and 34 weeks with an AFI between 5 and 8 em were not more likely than those with an AFI above 8 em to be complicated by maternal hypertension, stillbirth, or neonatal death. That said, higher rates of preterm delivery, cesarean delivery for a nonreassuring fetal heart rate pattern, and fetal-growth restriction were found. Wood and colleagues (2014) similarly reported a higher rate of fetal-growth restriction in pregnancies with borderline AFI. Thus, results evaluating pregnancy outcomes with borderline AFI have been mixed. Magann and associates (2011) concluded that evidence is insuicient to support fetal testing or delivery in this setting.
Abele H, Starz S, Hoopmann M, et al: Idiopathic polyhydramnios and postnatal abnormalities. Fetal Diagn Ther 32(4) :251, 2012
American College of Obstetricians and Gynecologists: Ultrasound in pregnancy. Practice Bulletin No. 175, December 2016
Biggio JR Jr, Wenstrom D, Dubard MB, et al: Hydramnios prediction of adverse perinatal outcome. Obstet Gynecol 94:773, 1999