Positive Prenatal Carrier Screening Result for Hemophilia: Obstetric Management Considerations
SUMMARY:
Hemophilia A and B are inherited bleeding disorders caused by a deficiency of clotting factor VIII (hemophilia A) or IX (hemophilia B) activity. Because they are X-linked, these conditions primarily affect males. Female carriers have varying levels of clotting factor activity and are at risk for excessive bleeding. In pregnancy, factor VIII levels rise which may reduce the risk of bleeding in hemophilia A carriers. There are special considerations for the care of hemophilia A and B carriers in pregnancy and childbirth due to potential bleeding in both the mother and the neonate.
Background
- Hemophilia A affects 1 in 6,500 males | Hemophilia B affects 1 in 30,000 males
- Symptoms in affected males range from mild to severe
- Prolonged bleeding
- Poor healing after injury or trauma
- Intracranial hemorrhage
- Spontaneous bleeding in joints
- Genetic female (46, XX) hemophilia carriers are at risk for
- Spontaneous bruising
- Menorrhagia
- Delayed healing after major trauma
- Postpartum hemorrhage
- Hemophilia A and B are included in the ACMG’s “Tier 3” recommendations for carrier screening, which should be offered to all patients who are pregnant or are considering pregnancy (see ‘Related ObG Topics’ below)
Genetics
- Hemophilia A and B are X-linked conditions
- Associated with pathogenic variants in the F8 (Hemophilia A) and F9 (Hemophilia B) genes
- For the offspring of female carriers
- Males have a 50% chance to be affected
- Females have a 50% chance to be carriers
- All daughters of affected males will be carriers
Diagnosis and Carrier Testing
- Diagnosis in affected males is established by clotting factor assays and may include genetic testing
- Hemophilia A: deficiency of clotting factor VIII with normal von Willibrand
sfactor
- Hemophilia B: deficiency of clotting factor IX
- Hemophilia A: deficiency of clotting factor VIII with normal von Willibrand
- Genetic testing of F8 or F9 is required to confirm carrier status in at-risk females
- An affected male should be the first person tested in a family in order to guide testing of other family members
- Normal factor levels do not rule out carrier status or risk for bleeding complications in at-risk females
Pregnancy Management for Hemophilia Carriers
- Factor VIII or IX clotting activity should be measured
- Prior to pregnancy
- Before any diagnostic procedures
- In the third trimester prior to delivery
- Hemophilia carriers are at an increased risk for bleeding with procedures or after spontaneous pregnancy loss, as well as during delivery and postpartum
- Prophylactic treatment with desmopressin or clotting factor concentrate is recommended prior to any uterine evacuation procedure
- Carrier status is not associated with increased risk of miscarriage
- Iron deficiency should be corrected early in pregnancy
- Referral for consultation with a high-risk obstetrician/hematologist and consideration of a multidisciplinary team at delivery if indicated
- Counsel about risk to offspring
- If fetus is male (by ultrasound or NIPS), offer prenatal diagnosis for familial hemophilia variant via CVS or amniocentesis
- External cephalic version is not recommended
Delivery Management
- Use of neuraxial anesthesia and mode of delivery should include
- Input from multidisciplinary team
- Shared patient decision making for obstetrical care
- Plan for administration of clotting factor concentrate (VIII or IX) at delivery if third trimester factor levels are <50%
- TXA or DDAVP (used to raise factor VIII levels) if clinically indicated
- The use of thromboprophylaxis (if indicated) should be discussed with hematology service
- Continue clotting factor replacement at least 5 days postpartum
If Fetus Affected Male or Prenatal Diagnosis Was Declined
- No fetal scalp electrodes or fetal blood sampling
- Consider unassisted vaginal delivery (no forceps or vacuum extractions) or planned cesarean delivery
- Collect cord blood at delivery for factor level and/or genetic testing
- Avoid circumcision until hemophilia A is excluded
- Postpartum vaccines
- Should be administered unless not recommended by hematology service
- Prolonged pressure should be given to the injection site
KEY POINTS:
- Hemophilia carriers are at increased risk for hemorrhage during delivery and postpartum
- Delivery should occur in a medical center with available support from a multidisciplinary team
- Male infants of hemophilia carriers have a 50% chance of being affected
- Neonates should be treated as if they are at risk for bleeding until affected status is ruled out
Learn More – Primary Sources:
Locate a Genetic Counselor or Genetics Services:
Locate a Maternal Fetal Medicine Specialist
Maternal Fetal Medicine Specialist Locator-SMFM
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