Lactose metabolism and time to pregnancy

Objective: To investigate whether, in the absence of galactosemia, relatively high intestinal lactase activity or low activity of an enzyme involved in galactose catabolism reduces fertility, as it does in the presence of galactosemia. Design: Retrospective cohort study. Setting: Healthy women selected from the community. Patients: Fifty-three married women. Intervention: Urinary galactose after an oral lactose challenge (a measure of intestinal lactase activity), erythrocyte galactose-1-phosphate uridyltransferase (transferase) activity, and transferase polymorphisms by isoelectric focusing. Main Outcome Measure: Pregnancy rate (number of pregnancies divided by number of months at risk) in the 12 months after stopping use of birth control to become pregnant. Results: Relatively high urinary galactose was not related to a decreased rate of pregnancy during the first 12 months (greater than or equal to 24.6 compared with less than or equal to 14.3 mg: relative risk [RR] = 1.9; 95% confidence interval [CI] = 0.86 to 4.0). Relatively high transferase activity was not related to an increased rate of pregnancy (greater than or equal to 19.5 compared with less than or equal to 17.2 mu mol/h per g hemoglobin: RR = 1.1; 95% CI = 0.56 to 2.4). Low-activity transferase polymorphisms were not related to a decreased rate (RR = 1.2, 95% CI = 0.58 to 2.5). Conclusion: Our study does not support the hypothesis that the biologic variation in galactose metabolism that exists in the general population influences infertility.