Polyhydramnios is a pathological excess of amniotic fluid. Common causes of polyhydramnios include fetal anomalies, gestational diabetes, multiple gestations, and congenital infections. Patients are often asymptomatic but may present with enlarged uterine size for gestational age, dyspnea, extremity swelling, or uterine contractions. Diagnosis is made based on ultrasound findings of an excessive amniotic fluid index ≥ 24 cm or single deepest pocket ≥ 8 cm. Polyhydramnios is associated with significant neonatal and maternal morbidity and mortality. Mild cases can resolve spontaneously; management of moderate-to-severe cases can include fetal monitoring, amnioreduction, administration of medications such as NSAIDs (e.g., indomethacin), and labor induction.
Last updated: 31 May, 2022
Polyhydramnios is an abnormally high level of amniotic fluid Amniotic fluid A clear, yellowish liquid that envelopes the fetus inside the sac of amnion. In the first trimester, it is likely a transudate of maternal or fetal plasma. In the second trimester, amniotic fluid derives primarily from fetal lung and kidney. Cells or substances in this fluid can be removed for prenatal diagnostic tests (amniocentesis). Placenta, Umbilical Cord, and Amniotic Cavity in the amniotic sac.
Normal physiologic conditions:
Two major causes of polyhydramnios:
Fundal heights throughout pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care in normal cases (left) and pregnancies complicated by polyhydramnios (right). The fundal height (FH) is the length between the pubic symphysis Pubic Symphysis A slightly movable cartilaginous joint which occurs between the pubic bones. Vagina, Vulva, and Pelvic Floor: Anatomy and the top of the fundus Fundus The superior portion of the body of the stomach above the level of the cardiac notch. Stomach: Anatomy. The FH measured in centimeters should be approximately equal to the fetus’ gestational age Gestational age The age of the conceptus, beginning from the time of fertilization. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last menstruation which is about 2 weeks before ovulation and fertilization. Pregnancy: Diagnosis, Physiology, and Care in weeks. For example, at 28 weeks, the FH should be ~ 28 cm. A discrepancy of > 3 cm is suspicious for polyhydramnios. The image on the left shows where the fundus Fundus The superior portion of the body of the stomach above the level of the cardiac notch. Stomach: Anatomy is located at different gestational ages throughout a normal pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care. The image on the right shows a potential progression of fundal growth in a pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care complicated by polyhydramnios. Notice how the FH at 28 weeks is significantly higher in the pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care complicated by polyhydramnios compared to a normal pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care.
Image by Lecturio.Classification of polyhydramnios | Amniotic fluid Amniotic fluid A clear, yellowish liquid that envelopes the fetus inside the sac of amnion. In the first trimester, it is likely a transudate of maternal or fetal plasma. In the second trimester, amniotic fluid derives primarily from fetal lung and kidney. Cells or substances in this fluid can be removed for prenatal diagnostic tests (amniocentesis). Placenta, Umbilical Cord, and Amniotic Cavity index (AFI) | Single deep pocket (SDP) |
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Mild | 24–29.9 cm | 8–11.9 cm |
Moderate | 30–34.9 cm | 12–15.9 cm |
Severe | ≥ 35 cm | ≥ 16 cm |
The photo demonstrates the measurement of a vertical pocket of amniotic fluid Amniotic fluid A clear, yellowish liquid that envelopes the fetus inside the sac of amnion. In the first trimester, it is likely a transudate of maternal or fetal plasma. In the second trimester, amniotic fluid derives primarily from fetal lung and kidney. Cells or substances in this fluid can be removed for prenatal diagnostic tests (amniocentesis). Placenta, Umbilical Cord, and Amniotic Cavity, which is used in the assessment of amniotic fluid Amniotic fluid A clear, yellowish liquid that envelopes the fetus inside the sac of amnion. In the first trimester, it is likely a transudate of maternal or fetal plasma. In the second trimester, amniotic fluid derives primarily from fetal lung and kidney. Cells or substances in this fluid can be removed for prenatal diagnostic tests (amniocentesis). Placenta, Umbilical Cord, and Amniotic Cavity volume. If this was the deepest fluid pocket present, it would be known as the single deepest pocket (SDP); values ≥ 8 cm are classified as polyhydramnios.
Image: “Demonstration of the technique to measure a single vertical pocket of liquor” by Kinare A. License: CC BY 2.0