Consanguinity and the risk of hyperemesis gravidarum in Norway

Background. Hyperemesis gravidarum (HG) is a condition that occurs in the first half of pregnancy, and is manifested by severe vomiting, electrolyte disturbances and weight loss. Previous studies have suggested the potential role of genetic factors in the aetiology of HG. We hypothesise that consanguineous relations between parents increase the risk of HG due to the increased risk of homozygosity in HG-associated alleles in a fetus. Moreover, we examine whether ethnic variations in the occurrence of HG can be attributed to consanguinity. Methods. All Norwegian, Pakistani and Turkish primiparous women with singleton pregnancies registered in the Norwegian Medical Birth Registry (MBRN) from 1967 to 2005 comprised the sample. Data on HG and potential confounders were obtained from MBRN. Multiple logistic regression was used to study associations between the degrees of relationship between women and their partners and the prevalence of HG. Crude and adjusted odds ratios (OR) with 95% confidence intervals (CI) were calculated. Results. The prevalence of HG was 0.9, 2.2 and 1.9% in Norwegian, Pakistani and Turkish women, respectively. Norwegian (OR =0.93; 95% CI: 0.42-2.09), Pakistani (OR =1.08; 95% CI: 0.68-1.74) and Turkish (OR =1.08; 95% CI: 0.44-2.67) women related to their partners as first cousins had similar risks of HG as non-related women after adjustment for potential confounders. Conclusions. Consanguinity was not associated with HG in this study. The differences in the occurrence of HG between Norwegian, Pakistani and Turkish women are not attributed to consanguinity.