Background: Sociodemographic studies of hyperemesis gravidarum are conflicting. During the last few years, there has been a clinical impression in Norway that immigrants are more afflicted than ethnic Norwegians.
Methods: Of 175 patients hospitalized with the diagnosis hyperemesis gravidarum 1993-1997, 120 had complete records and were compared to a control group of 115 patients without hyperemesis gravidarum, drawn at random from the labor ward protocol.
Variables: Ethnicity, age, height, weight at the beginning and at the end of pregnancy, body mass index, gravidity, parity, smoking, gestational age at labor, birth weight, placental weight. The patient's first name was used as an indication of ethnicity. Having a non-Norwegian name means, in the majority of cases, being a first generation immigrant from a developing country.
Statistics: SPSS statistical package for regression analyses, the chi-square test with Yates correction and the Mann-Whitney U-test.
Results: Risk factors for hyperemesis: non-Norwegian name (OR 3.4, 95% CI 1.5-7.6), female sex of the infant (OR 2.6, 95% CI 1.3-5.3), gravidity number (OR 1.4, 95% CI 1.1-1.9). These two last variables were of significance only in patients with a Norwegian name. The hyperemesis group had a lower weight gain and birth weight. In a stepwise multiple regression birth weight (g) was dependent on weight increase (kg) (B=19.0, p=0.001), weight in early pregnancy (kg) (B=8.0, p =0.02) and parity (B= 107.1, p=0.02). Hyperemesis, when corrected for weight increase, did not influence birth weight.
Conclusions: Risk factors vary between different populations. Hyperemesis patients are at risk of having infants with reduced growth.