Folic acid should be taken at a daily dose of 400 mcg or, in those who are obese, 5 mg. There is debate about the restriction of fertility treatment to women who are overweight, although there is no doubt that obesity has a significant adverse impact on reproductive outcome. It influences not only the chance of conception but also the response to fertility treatment and increases the risk of miscarriage, congenital anomalies and pregnancy complications [1]. The British Fertility Society guidance suggests that treatment should be deferred until the BMI is less than 35 kg/m2, although in those with more time (e.g. less than 37 years, normal ovarian reserve) a weight reduction to a BMI of less than 30 kg/m2 is preferable [2]. Even a moderate weight loss of 5–10% of body weight can be sufficient to restore fertility and improve metabolic parameters.