Purpose: To evaluate the burden of illness caused by hyperemesis gravidarum (HG) and association of readmissions due to HG with maternal, environmental and pregnancy-related factors, and different pregnancy outcomes.

Methods: Data of women with HG diagnosis in Finland, 2005-2017, were retrieved from health-care registers. Associations between readmissions due to HG and age, gravidity, parity, pre-pregnancy body mass index (BMI), smoking, marital status, socioeconomic status, municipality population, assisted reproductive technology (ART), and number and sex of fetuses were analyzed in pregnancies resulting in delivery. Admissions and readmissions due to HG in deliveries, gestational trophoblastic disease, ectopic pregnancies, miscarriages and pregnancy terminations were calculated.

Results: 10,381 pregnancies with HG diagnosis were identified: 9518 live births, 31 stillbirths, 8 cases of gestational trophoblastic disease, 16 ectopic pregnancies, 299 miscarriages, and 509 pregnancy terminations. Both outpatients and inpatients were included. Readmission occurred in 60% of pregnancies, inpatient readmission in 17%. Parity of ≥ 5, multiple gestation and female sex of fetus were associated with higher odds of readmission, maternal age 36-40 years, BMI ≥ 35 kg/m², smoking and ART with lower odds of readmission. Of the 9549 pregnancies resulting in delivery, 33% involved at least one outpatient visit or inpatient episode after the first trimester, and 8% in the third trimester.

Conclusion: The majority of women suffering from HG needed repeated medical care, often persisting after the first trimester. Our results provide practical information allowing clinicians to prepare for symptom duration beyond the first trimester and emphasize the importance of planning for eventual long-term treatment.