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Risk of fetal chromosomal abnormalities in idiopathic polyhydramnios
1Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taitong, Taiwan, R.O.C.
Insights
Fetal chromosome analysis is recommended for pregnancies with idiopathic polyhydramnios, as it reveals a higher incidence of chromosomal abnormalities than previously thought. This testing can prevent unnecessary interventions and the delivery of infants with genetic conditions.
Area of Science:
- Prenatal Diagnosis
- Medical Genetics
- Obstetrics
Background:
- Polyhydramnios (excess amniotic fluid) is often linked to fetal anatomical defects, prompting genetic testing.
- However, chromosome analysis in cases of idiopathic polyhydramnios (no apparent cause) is frequently overlooked.
- This study evaluates the necessity of genetic testing in pregnancies with idiopathic polyhydramnios.
Purpose of the Study:
- To determine the incidence of chromosomal abnormalities in fetuses with idiopathic polyhydramnios.
- To assess the clinical utility of fetal chromosome analysis in these pregnancies.
Main Methods:
- Genetic amniocentesis or percutaneous umbilical blood sampling was performed on 33 pregnancies with idiopathic polyhydramnios (26-34 weeks gestation).
- Level II sonography was used to identify fetal anatomical defects, and autopsy findings were compared with prenatal ultrasound results in four cases with abnormal karyotypes.
Main Results:
- Chromosomal abnormalities were detected in 7 of 33 (21.2%) cases of idiopathic polyhydramnios.
- After excluding cases with maternal age over 34 and false idiopathic diagnoses, the incidence of abnormalities in younger mothers was 8.3% (2/24).
- Three cases initially diagnosed as idiopathic polyhydramnios were found to have fetal anatomical defects upon re-examination.
Conclusions:
- The incidence of chromosomal abnormalities in idiopathic polyhydramnios is significantly higher than the risk associated with maternal age alone (34 years).
- Fetal chromosome analysis is recommended for pregnancies with idiopathic polyhydramnios.
- This testing can help avoid unnecessary Cesarean sections and the delivery of infants with undetected chromosomal abnormalities.
Background:
Polyhydramnios is often associated with fetal anatomical abnormalities; thus chromosome analysis is indicated for fetuses with those indications. However, chromosome analysis for patients with idiopathic polyhydramnios is often overlooked. This is an attempt to evaluate the necessity for chromosome analysis in pregnancies with idiopathic polyhydramnios.
Methods:
Genetic amniocentesis or percutaneous umbilical blood sampling was done in 33 cases with idiopathic polyhydramnios which appeared at 26 to 34 weeks' gestation. To exclude false idiopathic polyhydramniotic cases, a level II sonographic examination was carefully performed for those fetuses with abnormal chromosome. Autopsy ultrasound examination and X-ray examination were done in four neonates with abnormal karyotypes, and the results were compared with prenatal sonographic findings.
Results:
Seven (21.2%) out of the 33 cases were, surprisingly found to have chromosomal abnormalities. Three out of the seven cases were diagnosed to have fetal anatomical defects, at a repeated level II sono-graphic examination. The incidence of fetal chromosome abnormalities in idiopathic polyhydramnios was 13.3% (4/30). After 7 cases of women older than 34 years and 3 cases with false idiopathic polyhydramnios were excluded, the incidence of chromosomal abnormalities in pregnancies of those under 34 years of age with idiopathic polyhydramnios was 8.3% (2/24).
Conclusions:
According to the results of this study and other papers, the incidence of chromosomal abnormalities in fetuses with idiopathic polyhydramnios is much higher than that for maternal age specific risk at 34 years of age. Therefore fetal chromosome analysis for pregnancies with idiopathic polyhydramnios is recommended to avoid unnecessary Cesarean sections and deliveries of viable babies with abnormal chromosomes.