Polyhydramnios

Symptoms

• Often, there are no noticeable symptoms, especially if the condition is mild or develops slowly.
• Sensation of a uterus or abdomen that feels larger than expected for your stage of pregnancy.
• Fundal height measurement larger than expected during a prenatal check-up.
• Shortness of breath (dyspnea), particularly when lying down, associated with moderate to severe cases.
• Abdominal discomfort or a feeling of tightness.
• Uterine contractions or irritability, which could indicate preterm labor.
• Swelling (edema) in the lower extremities, vulva, or abdominal wall.
• Heartburn (pyrosis) and constipation due to pressure from the enlarged uterus.
• Difficulty for your healthcare provider to feel your baby's parts or hear the fetal heart clearly during an examination.
• Severe shortness of breath or inability to breathe comfortably (emergency symptom).
• Regular, painful uterine contractions, which are signs of preterm labor (emergency symptom).
• A sudden gush of fluid from your vagina, suggesting premature rupture of membranes (PROM) (emergency symptom).
• A sudden decrease in your baby's movements (emergency symptom).

Causes & Risk Factors

• Idiopathic: In 50-60% of cases, particularly mild polyhydramnios, no specific cause is identified.
• Maternal Diabetes: Poorly controlled diabetes (pre-existing or gestational) can lead to increased fetal urination.
• Fetal Anomalies: Conditions that impair fetal swallowing (e.g., anencephaly, esophageal atresia, duodenal atresia, facial clefts, thoracic masses) or increase fetal urine production (e.g., fetal anemia causing a high-output cardiac state, Bartter syndrome, sacrococcygeal teratoma).
• Multiple Gestation: Twin-to-twin transfusion syndrome (TTTS) in monochorionic twin pregnancies, where the recipient twin develops polyuria.
• Fetal Infections: Infections such as parvovirus B19, cytomegalovirus (CMV), toxoplasmosis, or syphilis, which can lead to fetal anemia or high-output states.
• Placental Tumors: A rare type of placental tumor called chorioangioma.
• Genetic/Chromosomal Syndromes: Conditions like Trisomy 18 or Trisomy 21 (Down syndrome).
• Polyhydramnios results from an imbalance in amniotic fluid dynamics, where conditions increase fluid production (fetal urination, lung secretions) or decrease fluid removal (fetal swallowing).
• Maternal Diabetes Mellitus: Both pre-gestational and gestational diabetes.
• Fetal Anomalies: Especially those affecting swallowing or increasing urine output, such as gastrointestinal obstruction, central nervous system abnormalities, neuromuscular disorders, thoracic masses, high-output cardiac states, and chromosomal abnormalities (e.g., Trisomy 21, 18).
• Fetal Anemia: For example, from Rh isoimmunization or parvovirus B19 infection.
• Placental Chorioangioma: A type of placental tumor.
• Multiple Gestation: Particularly monochorionic twin pregnancies with Twin-to-Twin Transfusion Syndrome (TTTS) in the recipient twin.
• Poor Glycemic Control: In women with maternal diabetes, this is a modifiable risk factor.
• The majority of mild polyhydramnios cases are idiopathic, meaning no specific risk factor or cause is identified.

Diagnosis

• Medical History: Review of your medical history for conditions like diabetes or isoimmunization, and any history of polyhydramnios or fetal anomalies in prior pregnancies. Family history of genetic conditions may also be reviewed.
• Physical Examination: Your healthcare provider may measure your fundal height, which might be greater than expected for your gestational age. They may also note a tense, smooth uterine wall or difficulty feeling fetal parts or hearing the fetal heart.
• Obstetric Ultrasound: This is the primary diagnostic tool.
• Amniotic Fluid Volume Assessment: Measurement of the Amniotic Fluid Index (AFI) or Single Deepest Pocket (SDP) to meet diagnostic criteria (AFI ≥ 24 cm or SDP ≥ 8 cm).
• Detailed Fetal Anatomic Survey: A comprehensive ultrasound to identify any structural anomalies in your baby, particularly in the gastrointestinal, central nervous, or cardiac systems.
• Fetal Biometry: Measurements of your baby's size to assess for macrosomia (a larger-than-average baby).
• Doppler Studies: May be used to assess for fetal anemia (e.g., Middle Cerebral Artery Peak Systolic Velocity - MCA-PSV) or to evaluate twin pregnancies for conditions like TTTS.
• Maternal Blood Tests: Glucose screening/testing for gestational diabetes, an antibody screen to detect red cell alloimmunization, and serology for infections if suspected (e.g., TORCH panel, Parvovirus B19).
• Invasive Fetal Testing (Amniocentesis): May be offered for fetal karyotype, microarray, or testing for specific genetic syndromes or infections, especially in cases of moderate to severe polyhydramnios or when fetal anomalies are present.
• Upon diagnosis, current guidelines recommend a comprehensive ultrasound evaluation for fetal anomalies, screening for gestational diabetes, and checking for red cell antibodies. Amniocentesis for karyotype/microarray should be offered, particularly in moderate to severe cases or when fetal anomalies are present.

Treatment Options

• Watchful Waiting (Expectant Management): Recommended for mild, idiopathic polyhydramnios without maternal symptoms or evidence of fetal compromise. This involves serial ultrasound surveillance of amniotic fluid volume and fetal growth, and potentially antenatal fetal testing (e.g., Non-Stress Test, Biophysical Profile) in the third trimester.
• Medical Treatment (Indomethacin): A medication that reduces fetal urine output. It may be considered for symptomatic polyhydramnios, typically before 32 weeks of gestation. Use is generally avoided after 32 weeks due to risks to the fetal heart and other complications. Evidence for improved perinatal outcomes is weak.
• Amnioreduction (Therapeutic Amniocentesis): An ultrasound-guided procedure to remove excess amniotic fluid. It is indicated for severe maternal symptoms (e.g., respiratory distress), preterm labor, or extreme uterine distention to relieve symptoms and potentially prolong pregnancy. Risks include premature rupture of membranes, preterm labor, placental abruption, and infection.
• Treatment of Underlying Cause: This includes strict glycemic control for maternal diabetes, intrauterine fetal transfusion for severe fetal anemia, or fetoscopic laser ablation for Twin-to-Twin Transfusion Syndrome (TTTS).
• A diagnosis of polyhydramnios generally warrants consultation with or transfer of care to a Maternal-Fetal Medicine (MFM) specialist.
• Current guidelines recommend against treatment for mild, idiopathic polyhydramnios. Amnioreduction is the preferred initial treatment for severe symptoms or preterm labor. Indomethacin may be considered for symptomatic polyhydramnios before 32 weeks but should not be used for more than 48-72 hours. Delivery timing should be individualized, with uncomplicated mild cases not recommended before 39 weeks, and moderate/severe cases potentially considering delivery between 37 and 39 weeks.

Frequently Asked Questions