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Risk of chromosomal abnormalities in patients with idiopathic polyhydramnios
K Brady1, W J Polzin, J N Kopelman
1Department of Obstetrics and Gynecology, Madigan Army Medical Center, Tacoma, Washington.
Insights
Idiopathic polyhydramnios, a condition of excess amniotic fluid, is linked to a higher incidence of fetal chromosomal abnormalities. Fetal chromosomal analysis is recommended for pregnant patients diagnosed with this condition.
Area of Science:
- Obstetrics and Gynecology
- Prenatal Diagnosis
- Medical Genetics
Background:
- Idiopathic polyhydramnios is defined as excess amniotic fluid in singleton pregnancies with normal fetal anatomy and maternal screening.
- The incidence of unexplained polyhydramnios in a primary care population was evaluated.
Purpose of the Study:
- To determine the incidence of chromosomal abnormalities in patients diagnosed with idiopathic polyhydramnios.
- To assess the diagnostic yield of amniocentesis in cases of unexplained polyhydramnios.
Main Methods:
- Prospective investigation of 5038 deliveries over a 2-year period.
- Sonographic identification of idiopathic polyhydramnios (Amniotic Fluid Index ≥ 25 cm).
- Amniocentesis performed on 125 patients with idiopathic polyhydramnios for chromosomal analysis.
Main Results:
- An incidence of 2.5% for unexplained polyhydramnios was observed.
- Four chromosomal abnormalities (3.2%) were detected in the 125 patients undergoing amniocentesis.
- Detected abnormalities included two cases of trisomy 18 and two cases of trisomy 21.
Conclusions:
- The incidence of aneuploidy in idiopathic polyhydramnios (3.2%) is significantly higher than in live births (0.59%).
- Fetal chromosomal analysis is recommended for all obstetric patients with sonographic evidence of idiopathic polyhydramnios.
Abstract:
This prospective investigation was designed to assess the incidence of chromosomal abnormalities in patients with idiopathic polyhydramnios. Polyhydramnios was defined as 25 cm or greater in total vertical height in all four quadrants (amniotic fluid index) in any nonreferral patient (ie, primary care population) undergoing sonographic examination with a singleton pregnancy, normal fetal anatomical survey, normal glucose screening, and negative antibody screen. During the 2-year period from May 1, 1988 through April 30, 1990, 5038 gravidas delivered at Madigan Army Hospital Center. Unexplained polyhydramnios was detected sonographically in 125 patients, an incidence of 2.5%. After obtaining informed written consent, amniocentesis was performed in all patients. Within this group (N = 125), four chromosomal abnormalities (incidence of 3.2%) were detected. There were two trisomy 18 and two trisomy 21 fetuses. None of the four patients had maternal serum alpha-fetoprotein screening performed. The incidence of aneuploidy in patients with idiopathic polyhydramnios (3.2%) is much higher than the reported incidence of major karyotype abnormalities in live births (0.59%). We conclude that fetal chromosomal analysis should be considered in all obstetric patients with sonographic evidence of idiopathic polyhydramnios.