Leisure-time physical activity before pregnancy and risk of hyperemesis gravidarum: a population-based cohort study.

Introduction: Women who experience severe nausea and vomiting in early pregnancy are less likely to participate in leisure-time physical activity (LTPA) during pregnancy. Whether LTPA before pregnancy is associated with hyperemesis gravidarum (HG) has not yet been studied. The aim of the study was to estimate associations between prepregnancy LTPA and HG in pregnancy.

Methods: We present data from 37,442 primiparous women with singleton pregnancies enrolled in The Norwegian Mother and Child Cohort Study. Prepregnancy LTPA was self-reported by questionnaire in pregnancy week 17. HG was reported in week 30 and defined as prolonged nausea and vomiting in pregnancy requiring hospitalisation before the 25th gestational week. We estimated the crude and adjusted associations between LTPA and HG using multiple logistic regression. We assessed effect modification by prepregnancy BMI or smoking by stratified analysis and interaction terms.

Results: A total of 398 (1.1%) women developed HG. Before pregnancy 56.7% conducted LTPA at least 3 times weekly, while 18.4% of women conducted LTPA less than once a week. Compared to women reporting LTPA 3 to 5 times weekly, women reporting no LTPA before pregnancy had an increased odds of HG (adjusted odds ratio (aOR) 1.69; 95% confidence interval (CI), 1.20 to 2.37). LTPA-HG associations differed by prepregnancy BMI but not by prepregnancy smoking.

Discussion: Lack of LTPA before pregnancy was associated with an increased odds of HG. Due to few cases of HG and thereby low statistical power, one need to be cautious when interpreting the results of this study.