This study looks at how the medicine hydroxyurea affects pregnant women with sickle cell disease (SCD) and their babies. Hydroxyurea helps treat SCD by stopping red blood cells from sickling, which is when they get a funny shape that can make people sick. Doctors worry that hydroxyurea might hurt pregnant women or their babies, but we don't know for sure because most of the information comes from lab tests, not real people. So, this study will check medical records from before June 20, 2019, to see what happened to women and their babies when the moms used hydroxyurea during pregnancy or breastfeeding. The goal is to understand if the medicine is safe for moms and their babies.

• This study uses old medical records up to June 20, 2019, so no new visits are needed.
• Participants' information must be about pregnancies or breastfeeding with SCD, exposed to hydroxyurea.
• No direct compensation is mentioned, but it helps learn about medicine safety during pregnancy.