What are some risk factors for hyperemesis gravidarum?

Unfortunately, a history of hyperemesis gravidarum in previous pregnancies is a significant risk factor for experiencing it in subsequent pregnancies. In studies that attempt to quantify the risk, the recurrence rate is as low as 15% and as high as 81%, partly related to the variety of definitions studies use for hyperemesis gravidarum.^[1] Infection with Heliobacter pylori might increase the risk or severity of hyperemesis gravidarum during pregnancy, and treatment of a confirmed infection is recommended.^[2] Other factors that may increase the risk of hyperemesis gravidarum include carrying a female fetus, family history of hyperemesis gravidarum, carrying more than one fetus, black or Asian ethnicity, type I diabetes, and younger age.^[3]