The influence of body mass index (BMI) on pregnancy outcomes among Japanese infertile women

Abstract

The World Health Organization defines obesity as BMI ≥30 kg/m2. Japan Society for the Study of Obesity (JASSO) defines obesity as BMI≥25 kg/m2. The objective of this study was to examine the effect of BMI on infertility treatment among Japanese women based on JASSO criteria. Retrospective study 859 patients undergoing infertility treatment from June 2006 to March 2010 were allocated into 3 main groups according to JASSO criteria:low (n = 152), normal (n = 648), and high (n = 59) BMI. They were further subdivided by treatment into 2 subgroups: no in vitro fertilization (IVF) (n = 421) and IVF (n = 438). The main outcome measures were pregnancy rate (PR), ongoing pregnancy rate (OPR), and miscarriage rate (MR). Statistics testing included Student's t-test, Pearson's chi square test. PR was significantly lower in the high BMI group (32/59, 54.2%) than in the normal BMI group (440/648,67.9%; P<0.05). Low BMI group showed no significant impact on fertility. Compared to IVF patients with normal BMI (n = 332), IVF patients with high BMI (n = 34) had a tendency towards lower PR (11/34, 32.3% vs. 117/332, 35.2%), OPR (6/11, 54.5% vs. 99/117, 84.6%), higher MR (5/11,45.4% vs.18/117, 15.3%), lower fertilization rate (164/301, 52.5% vs. 2257/3898, 57.9%); a significant reduction in the number of oocytes retrieved (8.8 vs. 11.7 ;P<0.05), in the number of good quality embryos (47/116, 40.5% vs. 873/1517,57.5%; P<0.05) and a significant increase in the number of bad quality embryos (29/116, 25% vs. 173/1517, 11.4%; P<0.05). Obesity has a deleterious effect on fertility.