What is included in the prenatal testing of hemophilia A carriers?

Updated: Jan 14, 2019
  • Author: Douglass A Drelich, MD; Chief Editor: Srikanth Nagalla, MBBS, MS, FACP  more...
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Answer

For prenatal testing, carriers whose mutation has been identified can have chorionic villus sampling at approximately 10-12 weeks' gestation or amniocentesis at 16-20 weeks' gestation to obtain fetal cells for DNA analysis or for linkage studies. If DNA analysis cannot be performed, then fetal blood obtained by fetoscopy at approximately 20 weeks' gestation can be assayed for factor VIII level.

All of those procedures carry a risk ranging from a low of 0.5% for maternal-fetal complications to a high of 1-6% for fetal death from fetoscopy. These procedures should be undertaken only after patients receive intense genetic and obstetric counseling. Genetic counseling before the woman becomes pregnant is ideal and may help couples make informed decisions before conception.

Noninvasive prenatal diagnosis using quantitative digital polymerase chain reaction testing of free fetal DNA in the maternal circulation has been reported. However, this technique remains a research tool. [24]

If the fetus is a female, the couple may elect to carry the pregnancy to term because carriers rarely have bleeding problems. If the fetus is a severely affected male, the couple must make a decision about continuing the pregnancy to term. With pregnancies that will be carried to term, prenatal diagnosis allows for planning of delivery so as to minimize the risk of intracranial hemorrhage (eg, avoidance of vacuum devices). [24]


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