Association of Obesity With Longer Time to Pregnancy.

OBJECTIVE: To assess whether obesity is associated with increased time to pregnancy in a cohort of participants who were stopping their contraceptive method to attempt pregnancy. METHODS: We performed a secondary analysis of the FACT (Fertility After Contraceptive Termination) study. This prospective analysis included 432 participants, aged 18-35 years, who discontinued contraception to become pregnant, were sexually active with a male partner, and provided pregnancy status data within the first 12 months in the study. The primary outcome, time to pregnancy, was measured beginning with discontinuation of contraception to estimated pregnancy date. We used Cox proportional hazard models to assess associations of normal (lower than 25.0), overweight (25.0-29.9), and obese (30 or higher) body mass index (BMI) and time to pregnancy while controlling for potential confounding factors. RESULTS: After adjusting for confounders, participants with BMIs 30 or higher were noted to have prolonged time to pregnancy compared with those with BMIs lower than 25 (adjusted hazard ratio [aHR] 0.62; 95% CI 0.44-0.89). The median time to pregnancy for participants with normal BMIs was 5.3 months (95% CI 3.8-6.4) compared with 8.2 months (95% CI 6.8-10.8) for participants with obesity. Pregnancy rates at 1 year were 76.4% (95% CI 69.7-82.6%), 69.5% (95% CI 60.5-78.1%), and 59.1% (95% CI 51.0-67.4%) for participants with BMIs lower than 25, 25-29.9, and 30 or higher, respectively. Menstrual irregularity was also associated with decreased fertility (aHR 0.67; 95% CI 0.46-0.97). CONCLUSION: Compared with participants with normal BMIs, we observed increased time to pregnancy for participants with obesity stopping contraception with the intention to become pregnant. Understanding the reasons for this association will be helpful to inform patients and guide clinical practice. FUNDING SOURCE: The FACT Study was funded, in part, by Bayer, CooperSurgical, and the Society of Family Planning.

The Operant Plantar Thermal Assay: A Novel Device for Assessing Thermal Pain Tolerance in Mice.

Pain is a multidimensional experience of sensory-discriminative, cognitive, and affective processes; however, current basic research methods rely heavily on response to threshold stimuli, bypassing the supraspinal processing that ultimately gives rise to the pain experience. We developed the operant plantar thermal assay (OPTA), which utilizes a novel, conflict-based operant task requiring evaluation and active decision-making to obtain reward under thermally aversive conditions to quantify thermal pain tolerance. In baseline measures, male and female mice exhibited similar temperature preferences, however in the OPTA, female mice exhibited greater temperature-dependent tolerance, as defined by choice time spent in an adverse thermal condition to obtain reward. Increasing reward salience (4% vs 10% sucrose solution) led to increased thermal tolerance for males but not females. To determine whether neuropathic and inflammatory pain models alter thermal tolerance, animals with chronic constriction injury (CCI) or complete Freund's adjuvant (CFA), respectively, were tested in the OPTA. Surprisingly, neuropathic animals exhibited increased thermal tolerance, as shown by greater time spent in the reward zone in an adverse thermal condition, compared with sham animals. There was no effect of inflammation on thermal tolerance. Administration of clonidine in the CCI model led to increased thermal tolerance in both injured and sham animals. In contrast, the non-steroidal anti-inflammatory meloxicam was anti-hyperalgesic in the CFA model, but reduced thermal pain tolerance. These data support the feasibility of using the OPTA to assess thermal pain tolerance to gain new insights into complex pain behaviors and to investigate novel aspects of analgesic efficacy.