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Aneuploidy in twin gestations: when is maternal age advanced?
1Department of Obstetrics, Gynecology, University of Maryland, Baltimore, USA.
Obstetrics and Gynecology
|February 1, 1997
Summary
Women with twin gestations aged 31 have a fetal aneuploidy risk similar to 35-year-old singleton pregnancies. Invasive prenatal diagnosis for fetal aneuploidy is recommended for all twin pregnancies at age 31.
Area of Science:
- Maternal-fetal medicine
- Prenatal diagnostics
- Genetics
Background:
- Maternal age is a primary risk factor for fetal aneuploidy.
- Twin gestations have unique considerations for aneuploidy screening.
- Dizygotic twinning rates vary by maternal age and race.
Purpose of the Study:
- To identify the maternal age for twin gestations with aneuploidy risk comparable to singleton pregnancies at age 35.
- To account for age and race-specific dizygotic twinning rates.
Main Methods:
- Utilized known aneuploidy risks and dizygotic twinning rates by maternal age and race.
- Calculated fetal aneuploidy risk in twin gestations at term and second trimester.
- Employed previously published calculation methodologies.
Main Results:
- At maternal age 31, the risk of at least one aneuploid twin at term is 1/193, similar to singletons at age 35 (1/192).
- For twin gestations at amniocentesis (age 31), aneuploidy risk is 1/190 (white) and 1/187 (African-American), lower than singletons (1/135).
Conclusions:
- Invasive prenatal diagnosis for fetal aneuploidy should be offered to all women with twin gestations at age 31.
- Race is not a determining factor for offering invasive prenatal diagnosis in this age group.