ORIGINAL ARTICLE Gestational carrier BMI and reproductive, fetal and neonatal outcomes: are the risks the same with increasing obesity? K Coyne 1 , LD Whigham 2 , K O'Leary 1,3 , JK Yaklic 1 , RA Maxwell 1 and SR Lindheim 1 OBJECTIVE: Data suggest that female obesity impairs uterine receptivity and increases the risk of fetal and neonatal mortality. We analyzed the reproductive outcomes of gestational carriers (GCs) undergoing donated oocytes and assisted reproductive technology according to body mass index (BMI). DESIGN: A retrospective analysis of 163 GCs undergoing 226 in vitro fertilization (IVF) and embryo transfer cycles. METHODS: GCs undergoing in vitro fertilization and embryo transfer cycles were analyzed and divided according to their BMI (healthy weight: 20 - 24.9 kg m –2 (n = 77 in 114 cycles); overweight: 25 - 29.9 kg m –2 (n = 55 in 71 cycles); and obese: 30 - 35 kg m –2 (n = 31 in 41 cycles)). All GCs underwent a complete medical evaluation and were cleared for pregnancy before being selected. Overweight and obese GCs also underwent a metabolic screening, including an oral glucose tolerance test and lipid profile. The main outcomes measured were clinical pregnancy and live birth rates, antenatal and neonatal outcomes. RESULTS: Clinical pregnancy and live birth rates were similar despite increasing BMI. There were no statistically significant differences in the implantation rates, clinical pregnancy rates or live birth rates per embryo transfer among patients in the three BMI groups. In the healthy weight, overweight and obese GCs, the clinical pregnancy rates per GC were 72%, 84% and 79%, and per embryo transfer rates were 52%, 49% and 56%, respectively; P = NS. The live birth rates per GC were 70%, 84% and 75%, and per embryo transfer rates were 50%, 49% and 53%, respectively; P = NS. Twin rates were similar between the groups (35%, 31% and 29%, respectively; P = NS). There were no differences in gestational diabetes, preterm admissions or cesarean section rates. Neonatal intensive care unit admissions were similar (11%, 13% and 12%, respectively; P = NS), and no maternal, neonatal or infant mortality occurred. CONCLUSIONS: These data show that increasing obesity does not impair the reproductive outcome in GC cycles. Larger sample size is indicated to verify these findings. Furthermore, this study suggests that the standard metabolic screening used for GCs may lead to selection of healthier patients compared with women of comparable BMI who conceive outside of a fertility clinic setting, indicating the metabolic profile, rather than BMI, may better explain differences in pregnancy outcomes. International Journal of Obesity advance online publication, 8 September 2015; doi:10.1038/ijo.2015.159 INTRODUCTION Obesity is the most common chronic disease in the United States and affects 4600 million adults worldwide. 1 Of the overweight and obese population in the United States, 35% and 60%, respectively, are women of reproductive age. 2 Obesity increases the risk of diabetes, hypertension, cardio- vascular disease, cerebrovascular disease, pancreatitis, sleep apnea, cancer and musculoskeletal disease. 3 In addition, the adverse effects of being overweight or obese on reproduction include menstrual dysfunction, ovulation and decline in natural fecundity. 4,5 Furthermore, obesity is now the most common complication of pregnancy in developed and developing countries. 6,7 In the United States, 12 - 38% of pregnancies are in overweight women and 11 - 40% are in obese women. 7 In the United Kingdom, a third of pregnant women are overweight or obese, while in China and India, 16 and 26% of pregnancies are in overweight or obese women. 7–10 The detrimental effects of obesity have also been reported in assisted reproduction, including suboptimal responses to ovarian stimulation and pregnancy outcomes in patients undergoing ovulation induction, in vitro fertilization (IVF) and ovum donation. 9,11 Maternal adiposity is associated with a range of adverse pregnancy outcomes regardless of the mode of concep- tion. These outcomes include gestational diabetes, pre-eclampsia, preterm birth, neonatal morbidity, such as fetal macrosomia, and childhood obesity with its host of metabolic disorders, including type 2 diabetes and cardiovascular disease. 10 These adverse effects may be especially pronounced in women with a body mass index (BMI) 430 kg m –2 , central adiposity and polycystic ovarian syndrome. 2,9 Data also suggest that even modest increases in maternal BMI are associated with an increased risk of fetal death, stillbirth and infant death. 8 The prevalence of assisted reproduction and use of gestational carriers (GCs) or surrogates, women who carry a pregnancy and give birth for another woman or couple, is on the rise. The number of assisted reproductive therapy (ART) cycles performed in the United States has increased by 32%, from 115,392 cycles in 2002 to 151,923 in 2011. 12 GCs were involved in ~ 1% of ART cycles using fresh non-donor embryos in the United States from 2005 to 2011. 13 Interestingly, according to the most recent Centers for Disease Control ART National Summary Report, the percentages of transfers that resulted in live births for ART cycles that used GCs 1 Department of Obstetrics and Gynecology, Boonshoft School of Medicine, Wright State University, Dayton, OH, USA; 2 Paso del Norte Institute for Healthy Living, El Paso, TX, USA and 3 Wright-Patterson USAF Medical Center, Dayton, OH, USA. Correspondence: Dr SR Lindheim, Department of Obstetrics and Gynecology, Boonshoft School of Medicine, Wright State University, 128 E. Apple Street, Suite 3811, Dayton, OH 45409, USA. E-mail: Steven.lindheim@wright.edu Received 22 April 2015; revised 11 July 2015; accepted 20 July 2015; accepted article preview online 20 August 2015 International Journal of Obesity (2015), 1 – 5 © 2015 Macmillan Publishers Limited All rights reserved 0307-0565/15 www.nature.com/ijo