Oligohydramnios

Expect an unhappy tracing - Oligohydramnios raises the risk of umbilical cord compression, fetal heart rate decelerations, nonreactive tracings, meconium aspiration, and cesarean delivery. Continuous electronic fetal monitoring is the read on how much time you have. Treat a labor epidural as your cesarean anesthetic in waiting and keep it dense enough to extend.

Maternal hydration matters - 1 to 2 L of oral or IV fluid during labor transiently raises amniotic fluid volume and reduces cord compression. When the OB asks for a bolus in this setting, there is a mechanism behind it.

Protect uteroplacental perfusion - This fetus has no fluid reserve and a cord that is already being squeezed. Keep left uterine displacement, treat hypotension promptly rather than watching it, and avoid letting the mother run dry.

Gestational age at diagnosis - Second-trimester oligohydramnios is far more likely to reflect a fetal or maternal anomaly and carries mortality as high as 90%, with pulmonary hypoplasia accounting for 87% of those deaths. Third-trimester diagnosis is idiopathic in about half of cases and carries an 85.3% survival rate. The number tells you what kind of delivery room you are walking into.

Have neonatal help present - Pulmonary hypoplasia after prolonged severe oligohydramnios means severe respiratory insufficiency from the first breath. Renal agenesis with the Potter sequence produces respiratory distress within an hour of birth and is not survivable. Do not let the neonatal team be a phone call away.

Find the cause - Ultrasound for maximum vertical pocket and fetal anatomy; look specifically for bladder outlet obstruction, posterior urethral valves, dysplastic kidneys, or renal agenesis, and for ruptured membranes. In a monochorionic twin pregnancy, oligohydramnios in one sac with polyhydramnios in the other is twin-twin transfusion syndrome (TTTS) until proven otherwise.

Timing of delivery - For isolated oligohydramnios with intact membranes, current recommendations support delivery at 37 weeks. Antepartum surveillance is weekly maximum vertical pocket measurement plus nonstress tests, with serial growth scans.

Oligohydramnios is a decreased amniotic fluid volume for gestational age — a maximum vertical pocket under 2 cm, or an amniotic fluid index under 5 cm. From about 16 weeks fetal urine becomes the dominant source of amniotic fluid, so genitourinary causes lead the list: bladder outlet obstruction, dysplastic kidneys, renal agenesis. It complicates 4.4% of pregnancies at term and under 1% of preterm pregnancies.

The deficit matters two ways. Mechanically, the cord loses its cushion, so labor brings umbilical cord compression, fetal heart rate decelerations, nonreactive tracings, meconium aspiration, and cesarean delivery. Developmentally, low fluid during the 16 to 24 week window when terminal sacs are forming produces pulmonary hypoplasia, plus limb contractures from compression of fetal parts.