Snapshot A 26-year-old G2P1 woman presents to her regular obstetrics checkup at 12 weeks gestation. She had been tolerating the pregnancy without issue. Her first pregnancy did not have any complications, and she had delivered a boy at 39 weeks via spontaneous vaginal delivery. On ultrasound, she is noted to have oligohydramnios. Further evaluation shows that the fetus has polycystic kidneys. (Oligohydramnios) Introduction Overview amniotic fluid is essential for fetal growth and development, protecting the fetus from trauma and infection, and aids the development of fetal lungs polyhydramnios abnormally high volume of amniotic fluid oligohydramnios abnormally low volume of amniotic fluid Overview of Polyhydramnios vs Oligohydramnios Polyhydramnios Oligohydramnios Epidemiology 1% of all pregnanices 11% of all pregnanices Etiology Congenital anomaly (most common) fetal gastrointestinal tract blockage (esophageal atresia and other intestinal atresia) Twin-twin transfusion syndrome Maternal diabetes Rupture of membranes (most common) Fetal urinary tract blockage (polycystic kidneys, posterior urethral valves, and renal agenesis) Maternal substance abuse Prognosis Usually associated with good prognosis Mortality rate is high, particularly if diagnosed in the first trimester Oligohydramnios can increase the fetal risk for chest wall fixation and pulmonary hypoplasia Prognosis polyhydramnios and oligohydramnios on their own are associated with good prognosis however, depending on the etiology, such as renal agenesis where mortality is 100%, prognosis varies Presentation Symptoms often asymptomatic may have abdominal discomfort if severe Physical exam large uterus (polyhydramnios) Imaging Ultrasound indication all patients findings can assess for amniotic fluid index (AFI) calculated by dividing the abdomen into four quadrants and using the largest vertical pocket of fluid to estimate the total volume polyhydramnios AFI > 24 cm oligohydramnios AFI < 7 cm fetal structure survey may also visualize any congenital abnormalities Differential Twin-twin transfusion syndrome key distinguishing factor monozygotic twin pregnancy with anastomotic vessel shunting from one fetus to another Treatment Medical prostaglandin synthetase inhibitors indication to reduce amniotic fluid volume maternal discomfort preterm labor modalities indomethacin complications closure of ductus arteriosus monitor with fetal echocardiograph with Doppler closure resolves within 24 hours of discontinuing indomethacin Surgical transabdominal amniocentesis indication polyhydramnios maternal discomfort preterm labor complications placental abruption fetal maternal hemorrhage fetal pneumothorax risk of infection transcervical amnioinfusion indications oligohydramnios to improve detection of fetal structural anomalies to prevent serious complications if severe short-term improvement complications amniotic fluid embolism maternal respiratory distress delivery at 37-38 weeks indications idiopathic olighydramnios Complications Oligohydramnios chest wall fixation pulmonary hypoplasia