The use of hydroxyurea may be safe up to the time of conception in women with sickle cell disease (SCD) wishing to become pregnant, a new study published in the American Journal of Hematology found. However, clinicians should continue to advise caution on its use during pregnancy.

Hydroxyurea is often used to reduce pain crises, acute chest syndrome, and blood transfusions in patients with sickle cell disease. Although the treatment may have potentially detrimental effects on fertility and birth outcomes, there are little data regarding its effects when taken during pregnancy.

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In the present study, a team of researchers from the United States assessed pregnancy outcomes in women with sickle cell disease using hydroxyurea. The researchers collected the pregnancy history, corresponding hydroxyurea use, and pregnancy outcomes in 1285 women with sickle cell disease, aged 18 to 45 years.

Of these 1285 women, 737 became pregnant. The total number of pregnancies was 1788. Of these, 1079 led to live births, 394 to miscarriages, 40 to stillbirths, and 207 to abortions. Forty-eight pregnancies were ongoing during the study. Outcome information was missing for 20 pregnancies. Of the live births, miscarriages, and stillbirths, 241 (15.9%) were conceived while the women were using hydroxyurea.

Statistical analyses revealed that more than 3 pregnancies, severe disease, a history of stillbirth or miscarriage, and chronic kidney disease at enrollment were significantly associated with miscarriage or stillbirth. 

The use of hydroxyurea during conception and pregnancy was associated with an increase in the odds ratio of miscarriage or stillbirth. However, this was not the case when hydroxyurea was used only during conception. 

When the researchers analyzed live births only, they found that the use of hydroxyurea during conception and pregnancy was associated with a birth weight of less than 5.5 pounds in full-term babies. Hydroxyurea use was not associated with prematurity or serious medical problems at birth.


Kroner BL, Hankins JS, Pugh N, et al; Sickle Cell Disease Implementation Consortium. Pregnancy outcomes with hydroxyurea use in women with sickle cell disease. Am J Hematol. Published online February 10, 2022. doi:10.1002/ajh.26495