Replacement therapy helped pregnant woman manage hem B
Case study details successful delivery without bleeding complications
Note: This story was updated June 11, 2025, to correct the number of weeks the woman in the case study was pregnant to 36.
A woman carrying a hemophilia B genetic mutation received regular factor IX (FIX) replacement therapy during pregnancy and successfully delivered her baby with no severe bleeding complications, a case study reported.
Due to a history of bleeding associated with miscarriages and vaginal bleeding during pregnancy, the 37-year-old woman sought care at a hospital in Tokyo. Although severe bleeds are rarely seen in female hemophilia carriers during pregnancy, the hospital’s approach to treatment and monitoring could be a guide for similar cases, according to the research team.
“We believe that this case can provide obstetricians with novel insights on the management of pregnant women with hemophilia,” they wrote.
The study, “Successful management with regular factor IX replacement during pregnancy in a hemophilia B carrier: A case report,” was published in the Journal of Obstetrics and Gynaecology Research.
Hemophilia is a rare disorder marked by uncontrolled bleeding episodes driven by deficiency in certain clotting proteins. In hemophilia B, excessive bleeding is caused by mutations in the F9 gene, which encodes FIX, a protein important in blood clotting. Factor replacement therapies, which supply the missing clotting factors, are generally considered the gold standard treatment for hemophilia.
Hemophilia B less common in women
Although hemophilia B is more common in boys and men because of the way the disease is disease is inherited, girls and women who carry F9 mutations can also experience bleeds.
The researchers described the case of a pregnant woman who was a hemophilia B carrier.
Her brother and uncle had been diagnosed with hemophilia B, and she likely inherited the genetic mutation from her mother, who was asymptomatic. At age 25, she showed abnormally low FIX activity on diagnostic blood tests, indicating that she was also a carrier.
Symptoms first arose when the woman experienced a miscarriage 10 weeks into pregnancy, her second early-term miscarriage. Her clinical team removed the contents of her uterus with a procedure called uterine evacuation. Although this did not cause excessive bleeding after her first miscarriage, it did after her second.
Clinicians initially controlled the bleeding with a transfusion of fresh, frozen plasma and a minimally invasive procedure used to block blood flow in the uterine artery. Four days later, the bleeding recurred, and the team administered BeneFIX (nonacog alfa), a FIX replacement therapy, which stopped the bleeding entirely.
Soon after her second miscarriage, the woman conceived for a third time. She experienced genital bleeding and a buildup of blood between the early placental tissue and the wall of the uterus, called a subchorionic hematoma. Testing revealed that her FIX activity levels were 15.8% of normal values.
“Due to difficulty in controlling massive bleeding in the previous miscarriage, management was changed with FIX replacement and monitoring at the start of the subsequent pregnancy,” the team wrote.
While BeneFIX kept bleeding under control, her FIX activity levels remained low. Clinicians treated her with Alprolix (eftrenonacog alfa), another lab-made FIX replacement therapy that’s engineered to last longer in the body (extended half-life therapy). At this point, genetic testing also confirmed her hemophilia B carrier status.
After 36 weeks of gestation, she experienced preeclampsia, a pregnancy complication characterized by high blood pressure. She had an unplanned cesarean section, during which she received Novact M, a plasma-derived FIX replacement therapy.
“This approach resulted in a successful delivery without any severe hemorrhagic complications,” they wrote. Throughout and immediately after surgery, the therapy maintained her FIX activity levels at around 50%, which is within normal bounds.
In the week following birth, the woman received maintenance therapy with a combination of extended half-life and plasma-derived FIX. Weekly extended half-life treatments continued for a month after surgery. Although the child, a girl, did not have any signs of postnatal bleeding, a test of her FIX activity at six months indicated she is likely also a hemophilia B carrier.
“Regular monitoring and factor replacement should be considered for pregnant women with hemophilia, particularly those with specific medical histories, as observed in the present patient,” the researchers wrote.
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