Extremities of body mass index and their association with pregnancy outcomes in women undergoing in vitro fertilization in the United States.
OBJECTIVE
To investigate the associations among underweight body mass index (BMI), pregnancy, and obstetric outcomes among women using assisted reproductive technology (ART).


METHODS
Retrospective cohort study using national data and log binomial regression.


METHODS
Not applicable.


METHODS
Women undergoing IVF in the United States from 2008 to 2013.


METHODS
None.


METHODS
Pregnancy outcomes (intrauterine pregnancy, live birth rates) per transfer, miscarriage rate per pregnancy, and low birth weight and preterm delivery rates among singleton and twin pregnancies.


RESULTS
For all fresh autologous in vitro fertilization (IVF) cycles in the United States from 2008 to 2013 (n = 494,097 cycles, n = 402,742 transfers, n = 180,855 pregnancies) reported to the national ART Surveillance System, compared with normal weight women, underweight women had a statistically significant decreased chance of intrauterine pregnancy (adjusted risk ratio [aRR] 0.97; 95% confidence interval [CI], 0.96-0.99) and live birth (aRR 0.95; 95% CI, 0.93-0.98) per transfer. Obese women also had a statistically decreased likelihood of both (aRR 0.94; 95% CI, 0.94-0.95; aRR 0.87; 95% CI, 0.86-0.88, respectively). Among cycles resulting in singleton pregnancy, both underweight and obese statuses were associated with increased risk of low birth weight (aRR 1.39; 95% CI, 1.25-1.54, aRR 1.26; 95% CI, 1.20-1.33, respectively) and preterm delivery (aRR 1.12; 95% CI, 1.01-1.23, aRR 1.42; 95% CI, 1.36-1.48, respectively). The association between underweight status and miscarriage was not statistically significant (aRR 1.04; 95% CI, 0.98-1.11). In contrast, obesity was associated with a statistically significantly increased miscarriage risk (aRR 1.23; 95% CI, 1.20-1.26).


CONCLUSIONS
Among women undergoing IVF, prepregnancy BMI affects pregnancy and obstetric outcomes. Underweight status may have a limited impact on pregnancy and live-birth rates, but it is associated with increased preterm and low-birth-weight delivery risk. Obesity negatively impacts all ART and obstetric outcomes investigated.
Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, School of Medicine, Emory University, Atlanta, Georgia; Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia. Electronic address: jennifer.kawwass@emory.edu.
Jennifer F
JF
Kawwass
Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia.
Aniket D
AD
Kulkarni
Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, School of Medicine, Emory University, Atlanta, Georgia; Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia.
Heather S
HS
Hipp
Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia.
Sara
S
Crawford
Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, School of Medicine, Emory University, Atlanta, Georgia; Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia.
Dmitry M
DM
Kissin
Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, School of Medicine, Emory University, Atlanta, Georgia; Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia.
Denise J
DJ
Jamieson
D000022:Abortion, Spontaneous / Q000209:etiology; D000328:Adult; D001724:Birth Weight; D015992:Body Mass Index; D016208:Databases, Factual; D005260:Female; D005298:Fertility; D005307:Fertilization in Vitro / Q000009:adverse effects; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007246:Infertility / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D050498:Live Birth; D009765:Obesity / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D016017:Odds Ratio; D011247:Pregnancy; D018873:Pregnancy Rate; D059285:Pregnancy, Twin; D047928:Premature Birth / Q000209:etiology; D012189:Retrospective Studies; D012307:Risk Factors; D013851:Thinness / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States
IVF; miscarriage; outcomes; preterm; underweight
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