What are the risks of oligohydramnios to the baby?

Risks of Oligohydramnios to the Baby

Oligohydramnios significantly increases the risk of stillbirth (2.6-fold), neonatal death, and multiple serious complications including pulmonary hypoplasia, fetal compression syndrome, and growth restriction. 1, 2

Mortality Risks

• Stillbirth risk is increased with an odds ratio of 2.6 in pregnancies complicated by oligohydramnios, representing the most critical mortality concern 1, 2
• Neonatal death within 28 days occurs more frequently, with an odds ratio of 3.18 compared to pregnancies with normal amniotic fluid 3
• The combination of fetal growth restriction with oligohydramnios creates particularly high mortality risk, warranting delivery between 34-37 weeks 1, 2

Severe Structural and Developmental Complications

• Pulmonary hypoplasia develops from prolonged oligohydramnios, particularly when occurring early in pregnancy, and can be devastating to neonatal survival 4
• Fetal compression syndrome (Potter sequence) results from chronic compression, causing characteristic facial features, limb contractures, and skeletal deformities 4
• These structural complications are most severe when oligohydramnios occurs before viability or persists throughout pregnancy 5, 4

Growth and Prematurity Complications

• Low birth weight (< 2.5 kg) occurs more frequently with an odds ratio of 2.10, with mean birth weight reduced by approximately 162 grams 3
• Preterm birth risk increases with an odds ratio of 2.73, often necessitated by worsening fetal status requiring early delivery 3
• Fetal growth restriction commonly accompanies oligohydramnios, particularly when caused by uteroplacental insufficiency 1, 2

Intrapartum and Immediate Neonatal Risks

• NICU admission rates are significantly elevated, occurring in 50% of cases with oligohydramnios versus 23-36% in those with normal fluid 6, 3
• Fetal distress during labor occurs more frequently, increasing cesarean delivery rates from 33% to 47% 6
• Umbilical cord compression during labor is more common due to reduced fluid cushioning, leading to non-reassuring fetal heart rate patterns 5

Underlying Anomaly Associations

• Genitourinary anomalies are the most common structural causes, including renal agenesis, multicystic dysplastic kidneys, and posterior urethral valves 1, 2
• Chromosomal abnormalities may be present, warranting karyotype consideration when oligohydramnios is detected 5
• A detailed fetal anatomical survey focusing on the genitourinary system is essential to identify these structural causes 2

Twin-Specific Risks

• In monochorionic twins, oligohydramnios in one sac indicates potential twin-twin transfusion syndrome with 10-30% risk of neurologic injury and 10% risk of co-twin demise 2
• The "stuck twin" phenomenon in severe cases predicts significant mortality risk requiring specialized management 1

Critical Clinical Pitfalls

• The severity of outcomes correlates with the degree and duration of oligohydramnios, with MVP < 1 cm representing severe disease requiring intensified surveillance 2
• Isolated oligohydramnios at term (without growth restriction or other complications) shows less dramatic differences in Apgar scores and pH, though stillbirth risk remains elevated 1, 2
• Delaying delivery after 34 weeks when oligohydramnios is associated with abnormal fetal surveillance significantly increases stillbirth risk 2