Women's prepregnancy lipid levels and number of children: a Norwegian prospective population-based cohort study

Objective To study prepregnancy serum lipid levels and the association with the number of children. Design Prospective, population-based cohort. Setting Linked data from the Cohort of Norway and the Medical Birth Registry of Norway. Participants 2645 women giving birth to their first child during 1994-2003 (488 one-child mothers and 2157 women with births) and 1677 nulliparous women. Main outcome measures ORs for no and one lifetime pregnancy (relative to pregnancies) obtained by multinomial logistic regression, adjusted for age at examination, education, body mass index (BMI), smoking, time since last meal and oral contraceptive use. Results Assessed in quintiles, higher prepregnant triglyceride (TG) and TG to high-density lipoprotein (TG:HDL-c) ratio levels were associated with increased risk of one lifetime pregnancy compared with having children. Compared with the highest quintile, women in the lowest quintile of HDL cholesterol levels had an increased risk of one lifetime pregnancy (OR 1.7, 95% CI 1.2 to 2.4), as were women with the highest low-density lipoprotein (LDL) cholesterol, TG and TG:HDL-c ratio quintiles (compared with the lowest) (OR 1.2, 95 /o CI 0.8 to 1.7; OR 2.2, 95% CI 1.5 to 3.2; and OR 2.2, 95% CI 1.5 to 3.2, respectively). Similar effects were found in women with BMI >= 25 and the highest LDL and total cholesterol levels in risk of lifetime nulliparity. Conclusion Women with unfavourable prepregnant lipid profile had higher risk of having no or only one child. These findings substantiate an association between prepregnant serum lipid levels and number of children. Previously observed associations between low parity and increased cardiovascular mortality may in part he due to pre-existing cardiovascular disease lipid risk factors.