Prenatal hydroxyurea shows no adverse pregnancy outcomes

Researchers have found no adverse impacts from taking hydroxyurea during pregnancy among sickle cell patients, presenting their findings at the American Society of Hematology 2025 Annual Meeting.¹

According to the authors, these findings provide reassurance about a lack of harm from prenatal hydroxyurea exposure during unplanned pregnancies or when it is needed to manage sickle cell complications in pregnant patients. However, they still recommended discontinuing the drug before pregnancy in case of unknown effects.

“Overall, the rate of live births was better than that seen in previous studies, and we had no maternal mortality, even though these patients were highly symptomatic,” said Anoosha Habibi, MD, lead study author and associate professor at Hôpitaux Universitaires Henri Mondor. “Based on these findings, we call for a pragmatic approach.”

Hydroxyurea use in sickle cell disease

Sickle cell complications prevented by hydroxyurea include painful vaso-occlusive crises and tissue damage. Current guidelines recommend women stop taking the drug 3 to 6 months before conception. Patients can receive blood transfusions as an alternative to hydroxyurea, but this option is not available in all countries and may not be safe in some patients.

The study was conducted to assess outcomes in women taking hydroxyurea during pregnancy. There were 245 pregnancies across 183 women attending 77 medical centers between 2009 and 2025 in Europe that were assessed.

Hydroxyurea use for multiple years before conception was reported in most of these women, with 84% taking hydroxyurea when they became pregnant. According to investigators, this indicates many of the pregnancies were possibly unplanned.

Pregnancy and birth outcomes

After exclusion of voluntary abortions, current pregnancies, and those discontinuing hydroxyurea use before conception, there were 178 pregnancies included in the final analysis. Live births were reported in three-fourths of these cases, with no instances of maternal death or hydroxyurea-related newborn malformations observed.

A rate of 17% was reported for miscarriage in patients taking hydroxyurea, which did not significantly differ from the prevalence reported in the general population. Preterm birth results were the same, with a rate of 17%. Maternal medical reasons led to 2 pregnancy terminations in hydroxyurea-exposed patients.

There were also 2 fetal deaths reported, the first of which was a late-term miscarriage before 21 weeks’ gestation, while the second while a stillbirth at 34 weeks’ gestation. Neither of these deaths were linked to hydroxyurea exposure.

Implications

These results indicated no evidence of adverse outcomes because of prenatal hydroxyurea use. Investigators concluded that hydroxyurea may be reasonable to use during pregnancy when sickle cell disease complications are more likely, and blood transfusion is not an option.

“In higher-resourced settings, we can manage treatment interruption and provide safe transfusions for most patients, but in many regions… the safety of transfusion is limited, or the access is simply unavailable,” said Habibi. “In those contexts, asking women to stop hydroxyurea may actually put them in danger of vaso-occlusive crises.”

Broader recommendations

This data adds to a growing body of evidence about managing sickle cell disease among pregnant patients, which was highlighted in global guidelines published by the World Health Organization in July 2025.² These guidelines highlighted the impact of sickle cell disease in low- and middle-income countries, where 95% of maternal mortality was reported in 2020.

To improve sickle cell disease management, investigators recommended that evidence-based policies be implemented. Additionally, further research is needed to fill evidence gaps about improving outcomes in this population.

“Pregnant women with [sickle cell disease] deserve skillful care that effectively manages the risks associated with their pregnancy, while supporting as positive an experience of pregnancy, childbirth, and the postnatal period as possible,” wrote investigators.

References

1. Study shows no clear evidence of harm from hydroxyurea use during pregnancy. American Society of Hematology. December 6, 2025. Accessed December 19, 2025. https://www.eurekalert.org/news-releases/1108371
2. Krewson C. WHO issues new global guidelines for managing sickle cell disease in pregnancy. Contemporary OB/GYN. July 28, 2025. Accessed December 22, 2025. https://www.contemporaryobgyn.net/view/who-issues-new-global-guidelines-for-managing-sickle-cell-disease-in-pregnancy