Obesity and fertility: a literature review of the association between parental obesity at the time of conception and embryo quality

Obesity [body mass index (BMI) ≥30 kg/m2] has been shown to be a risk factor in reducing the rate of successful in vitro fertilization (IVF) outcomes. In this systematized literature review, we investigate whether embryo quality specifically is affected by single-parent obesity (maternal or paternal) and obesity in both parents at the time of conception. We systematically searched for studies published over the last 10 years that graded embryo quality in conventional IVF and intracytoplasmic sperm injection procedures. Studies that did not use measured weight and height for BMI calculation were excluded. Ten eligible articles were found across 13 public databases. Comparing the results of 1845 couples, both female and male obesity independently caused faster preimplantation embryo development (P <0.05). The fertilization rate was not affected by either female, male, or combined parental obesity (P>0.05). Day 3 embryo quality does not seem to be affected by either female or male obesity alone. The 2 studies that investigated the effect of combined parental obesity on embryo quality reached contradictory findings. Male, but not female, >7% BMI reduction following bariatric surgery significantly increased the number of top-quality embryos compared with their results before surgery (P<0.05). We conclude that embryos of couples with single-parent obesity are not of lower quality compared with those of normal-weight parents. Combined parental obesity may affect embryo quality. BMI reduction could lead toward a successful outcome in obese infertile couples, regardless of whether they are undergoing IVF or not.