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Down syndrome maternal serum marker screening after 18 weeks' gestation
Françoise Muller1, Sophie Dreux, Jean-François Oury
1Service de Biochimie, Hôpital Ambroise Paré, Boulogne, France. francoise.muller@apr.ap-hop-paris.fr
Prenatal Diagnosis
|November 9, 2002
Summary
Maternal serum screening for Down syndrome using alpha-feto protein (AFP) and beta-human chorionic gonadotrophin (beta-hCG) is effective later in pregnancy. This screening is feasible from 18 weeks gestation, offering benefits to women with late prenatal care access.
Area of Science:
- Prenatal diagnostics
- Biochemistry
- Genetics
Background:
- Late access to prenatal care can limit screening options for Down syndrome.
- Maternal serum screening is a common method for assessing Down syndrome risk.
Purpose of the Study:
- To establish reference values for AFP and beta-hCG in later pregnancy.
- To assess the diagnostic accuracy of maternal serum marker screening from 18-35 weeks gestation for Down syndrome.
Main Methods:
- Analyzed 4072 sera from unaffected pregnancies and 118 from Down syndrome-affected pregnancies.
- Established reference values for alpha-feto protein (AFP) and free beta-human chorionic gonadotrophin (beta-hCG).
- Evaluated screening performance using a 1/250 risk cut-off.
Main Results:
- A detection rate of 72.9% with a 7.51% false-positive rate was achieved at 18-35 weeks gestation.
- These results were comparable to those from earlier screening (14-17 weeks).
- Detection rates varied by maternal age, with higher rates in women aged 35 and over (84.8%).
Conclusions:
- Maternal serum marker screening for Down syndrome is feasible and effective from 18 weeks gestation onwards.
- This extended screening window can benefit women who access prenatal care later in pregnancy.
- The study confirms the utility of AFP and beta-hCG screening in later gestation for Down syndrome risk assessment.