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

Abstract

OBJECTIVE: The World Health Organization defines obesity as BMI ≥ 30 kg/m. The Japan Society for the Study of Obesity (JASSO) defines obesity as BMI ≥ 25 kg/m. The objective of this study was to examine the effect of BMI on infertility treatment in Japanese women based on JASSO criteria.DESIGN: Retrospective studyMATERIALS AND METHODS: 616 patients undergoing infertility treatment from June 2006 to June 2007 were allocated into 3 main groups according to the JASSO criteria: low (n= 112), normal (n= 460), and high (n= 44) BMI. They were further subdivided by treatment into 2 subgroups: no in vitro fertilization (IVF) (n= 302) and IVF (n= 314). The main outcome measures were pregnancy rate (PR), ongoing pregnancy rate (OPR), and miscarriage rate (MR). Statistical testing included Student's t-test, Pearson's chi square test, and Fisher's exact test.RESULTS: PR was significantly lower in the high BMI group (22/44, 50%) than in the normal BMI group (318/460, 69.1%; P<0.05). Low BMI had no significant impact on fertility. Compared to IVF patients with normal BMI (n= 238), IVF patients with high BMI (n = 25) had: a tendency towards lower PR (5/25, 20% vs. 55/238, 23.1%), OPR (3/5, 60% vs. 41/55, 74.5%.), MR (2/5, 40% vs. 14/55, 25.5%), and fertilization rate (115/219, 52.5% vs. 1658/2832, 58.5%); a significant reduction in the number of oocytes retrieved (8.8±5.7 vs. 11.9±8.8; P<0.05) and the number of good quality embryos (33/90, 36.7% vs. 656/1118, 58.7%; P<0.05); and a significant increase in the cancellation rate due to poor response or lack of fertilization (5/25, 20% vs. 18/238, 7.6%; p<0.05).CONCLUSIONS: Obesity has a deleterious effect on fertility. This is clearly obvious among high BMI women seeking IVF, who showed fewer retrieved oocytes, a deterioration in embryo quality. No significant difference was observed in the implantation rate between normal BMI and high BMI women. However, the low fertilization and cleavage rates, possibly due to the bad quality embryos, may explain the poor outcomes in high BMI women. OBJECTIVE: The World Health Organization defines obesity as BMI ≥ 30 kg/m. The Japan Society for the Study of Obesity (JASSO) defines obesity as BMI ≥ 25 kg/m. The objective of this study was to examine the effect of BMI on infertility treatment in Japanese women based on JASSO criteria. DESIGN: Retrospective study MATERIALS AND METHODS: 616 patients undergoing infertility treatment from June 2006 to June 2007 were allocated into 3 main groups according to the JASSO criteria: low (n= 112), normal (n= 460), and high (n= 44) BMI. They were further subdivided by treatment into 2 subgroups: no in vitro fertilization (IVF) (n= 302) and IVF (n= 314). The main outcome measures were pregnancy rate (PR), ongoing pregnancy rate (OPR), and miscarriage rate (MR). Statistical testing included Student's t-test, Pearson's chi square test, and Fisher's exact test. RESULTS: PR was significantly lower in the high BMI group (22/44, 50%) than in the normal BMI group (318/460, 69.1%; P<0.05). Low BMI had no significant impact on fertility. Compared to IVF patients with normal BMI (n= 238), IVF patients with high BMI (n = 25) had: a tendency towards lower PR (5/25, 20% vs. 55/238, 23.1%), OPR (3/5, 60% vs. 41/55, 74.5%.), MR (2/5, 40% vs. 14/55, 25.5%), and fertilization rate (115/219, 52.5% vs. 1658/2832, 58.5%); a significant reduction in the number of oocytes retrieved (8.8±5.7 vs. 11.9±8.8; P<0.05) and the number of good quality embryos (33/90, 36.7% vs. 656/1118, 58.7%; P<0.05); and a significant increase in the cancellation rate due to poor response or lack of fertilization (5/25, 20% vs. 18/238, 7.6%; p<0.05). CONCLUSIONS: Obesity has a deleterious effect on fertility. This is clearly obvious among high BMI women seeking IVF, who showed fewer retrieved oocytes, a deterioration in embryo quality. No significant difference was observed in the implantation rate between normal BMI and high BMI women. However, the low fertilization and cleavage rates, possibly due to the bad quality embryos, may explain the poor outcomes in high BMI women.