Objective: To evaluate the association patterns and quantify the effects of lifestyle on time to pregnancy (TTP).
Design: Observational study.
Setting: Teaching hospitals in Hull, United Kingdom.
Patient(s): Two thousand and one hundred twelve consecutive pregnant women.
Intervention(s): A questionnaire inquiring about TTP, contraceptive use, pregnancy planning, previous subfertility/pregnancies, age, and lifestyle characteristics of either partner.
Main outcome measure(s): We compared TTP, conception rates, and relative risk of subfecundity between subgroups with different lifestyle characteristics.
Result(s): We found that TTP was significantly longer if the woman or partner smoked >15 cigarettes/day (P<.001 and.04, respectively), the partner consumed >20 alcohol units/week (P<.001), the woman's body mass index was >25 kg/m(2) (P<.001), their coffee and/or tea intake was >6 cups/day (P=.04), or if they were socially deprived (P<.001). Each of these effects remained unchanged after adjusting for the potential confounders. The relative-risks of subfecundity with each of these variables ranged between 1.4 to 1.9 (1.4 to 3.6 after adjustment). The effects of coital frequency and recreational drug use were insignificant. Couples who had >4 negative lifestyle variables had a sevenfold longer TTP; their conception probabilities fell by 60%, and they were 7.3-fold more likely to be subfecund than those without negative variables.
Conclusion(s): Lifestyle has a significant and cumulative impact on fecundity. Dose-dependent effects occur with smoking, alcohol, and tea/coffee consumption. Appropriate counseling could result in substantial reductions in the referrals for fertility investigations and treatments.