Hyperemesis Gravidarum: Risk of Recurrence in Subsequent Pregnancies.

This study aimed to examine whether the recurrence risk of hyperemesis gravidarum (HG) is modified by the timing of diagnosis, the severity of illness, and interpregnancy interval. The Kaiser Permanente Southern California 1998-2020 longitudinally linked medical records were used to examine the recurrence risk of HG in the first two (n = 93,444) and first three (n = 17,492) successive pregnancies. The timing of diagnosis- and the severity of illness-specific recurrence risks were examined by estimating the adjusted relative risks (aRR). The risks of HG in the second pregnancy among patients with and without previous HG were 23.8% and 3.4%, respectively (aRR: 8.20; 95% confidence interval [CI]: 7.52, 8.94). The recurrence risk persisted regardless of the trimester at diagnosis and the gestational age of delivery in the first pregnancy. The recurrence risk was greater for patients with metabolic disturbances requiring in-hospital treatment (30.0%) than those managed on an outpatient basis (18.6%) in the first pregnancy (aRR: 10.84 95% CI: 9.66, 12.16). Although Asian/Pacific Islander (RR = 12.9) and White (RR = 8.9) patients had higher HG recurrence risk regardless of the gestational age at delivery in the first pregnancy, all patients had significant recurrence risk only if their first pregnancy was delivered after 32 weeks of gestation. African American patients had the highest recurrence rate (34.4%). HG recurrence risk was unaffected by interpregnancy interval and correlated with the number of previous pregnancies complicated by HG. There is an increased recurrence risk of HG in subsequent pregnancies that is influenced by race/ethnicity and gestational age at delivery. The number of pregnancies complicated by HG synergistically adds to the recurrence risk.