Objective: To assess the effect of moderate obesity on the outcome of induction of ovulation with low dose gonadotrophin in women with polycystic ovary syndrome (PCOS).
Design: Retrospective analysis of women with PCOS treated consecutively. An analysis of the impact of obesity on outcome of pregnancy using data from the North West Thames Regional (NWTR) obstetric database was included for comparison.
Setting: Induction of ovulation clinic at the Samaritan Hospital for Women (St. Mary's Hospital Group).
Subjects: 100 women with clomiphene-resistant anovulation associated with PCOS. 75 were of normal weight (BMI 19-24.9 kg/m2, lean group) and 25 were moderately overweight (BMI 25-27.9 kg/m2, obese group).
Interventions: Induction of ovulation using low doses of gonadotrophins with small, stepwise increments in dosage as required.
Main outcome measures: Rates of ovulation, pregnancy and miscarriage; daily and total doses of gonadotrophin required for induction of ovulation.
Results: The proportion of ovulatory cycles was significantly greater in the lean group (77%) compared with the obese group (57%) (chi 2 9.8, P less than 0.001). Obese women required larger doses of gonadotrophin to achieve ovulation (P less than 0.001). The proportion of women who achieved at least one pregnancy was similar in the two groups (39% vs 48%) but miscarriage was more frequent in the obese group (60% vs 27%; P less than 0.05). This difference was independent of the baseline and/or mid-follicular luteinizing hormone (LH) concentration either before or during treatment. Analysis of data from the North West Thames Health Region obstetric database confirmed an increased risk of miscarriage in moderately obese women which was independent of maternal age.
Conclusions: Moderate obesity in women with PCOS, treated with low dose gonadotrophin, is associated with an increased risk of miscarriage. This is reflected in the results of analysis of the effect of obesity on outcome of pregnancy in the general population. It is therefore important to encourage weight reduction in obese women with PCOS before considering therapy to induce ovulation.