ASH 2025 Reassurance for pregnant SCD patients taking hydroxyurea

medwireNews: Taking hydroxyurea for sickle cell disease (SCD) shortly before or during pregnancy was not associated with worse maternal or neonatal outcomes in the prospective ESCORT-HU and ESCORT-HU Extension cohort studies.

Reporting the findings at the 67th ASH Annual Meeting & Exposition, investigator Anoosha Habibi (Hôpitaux Universitaire Henri-Mondor, Créteil, France) said that in almost 250 pregnancies exposed to hydroxyurea, there were no maternal deaths and no treatment-related malformations among newborns.

“These results are quite reassuring,” she told the audience in Orlando, Florida, USA. “Accidental or early exposure to hydroxyurea may not be as harmful as previously feared.”

Habibi continued: “Although discontinuation of [hydroxyurea] is recommended when pregnancy is planned, [hydroxyurea] may be continued when transfusion is not an alternative, particularly in patients with a history of [delayed hemolytic transfusion reactions].”

She explained that “SCD patients planning pregnancy are generally advised to discontinue [hydroxyurea] 3 to 6 months before conception,” but “evidence regarding [hydroxyurea]-associated teratogenicity in humans remains limited and inconclusive.”

The ESCORT-HU (2009–2019) and ESCORT-HU Extension (2020–2025) noninterventional cohort studies were conducted in 77 centers across France, Greece, Germany, and Italy as part of a post-marketing commitment to the European Medicines Agency following the approval of hydroxyurea for SCD.

Of the 3145 patients enrolled in the studies, 1733 (55%) were women, and just under half of them (45%; n=785) were of childbearing age (18–45 years). The majority of these women were not using contraception despite the hydroxyurea treatment.

A total of 245 pregnancies in 183 women were reported during the studies, of which 207 were in women with hydroxyurea exposure and just 36 were in women who had stopped hydroxyurea before conception (the status was unknown for two). The mean age at pregnancy was 30.7 years and the mean hydroxyurea dose was 16 mg/kg per day.

Hydroxyurea treatment was stopped in the first trimester in 61.8% of patients and in the second trimester in 6.5%. In 2.0% of patients, treatment was started in the second trimester, and 9.3% continued treatment throughout pregnancy.

Only one congenital malformation was reported during the course of the studies – a case of pyelocaliceal junction abnormality in an infant of a woman exposed to hydroxyurea for the first 2 weeks of her pregnancy. But this was not considered related to the treatment by the investigators.

There were no maternal deaths during the studies, in either the hydroxyurea exposed or nonexposed groups, a finding that the presenter described as “remarkable,” as maternal mortality is known to be higher among SCD patients than the general population.

Overall, 74% of pregnancies – both among women with and without hydroxyurea exposure – resulted in live births, with miscarriages occurring in a respective 17% and 22% of cases.

Of the nine women who received hydroxyurea throughout their pregnancy and had a live birth, five were to term and four premature.

There was just one case of stillbirth, in a woman exposed to hydroxyurea during the first month of pregnancy. But Habibi highlighted that “no evident malformation or causal relationship with hydroxyurea exposure was reported by the investigators.”

Twelve percent of women in the hydroxyurea-exposed group opted for voluntary abortions compared with none in the nonexposed group. Three pregnancies were terminated due to medical reasons – two in the exposed group and one in the nonexposed group. All were required because of the severity of maternal complications, reported the presenter.

She concluded that “further studies including larger numbers of hydroxyurea-exposed pregnancies and long-term follow-up of children are needed.”

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67th ASH Annual Meeting & Exposition; Orlando, Florida USA: 6–9 December 2025