AUTHORS:  Sneed ML, Uhler ML, Grotjan HE, et al.
PLACE OF STUDY:  Lutheran General Hospital, Park Ridge, Illinois, USA
PUBLICATION:  Human Reproduction
PUBLICATION DATE:  May 2008 
ABSTRACT:

BACKGROUND: The objective of this study was to examine the effect of BMI on IVF outcomes. METHODS: This was a retrospective analysis of all patients undergoing IVF from 1st January 2005 to 1st March 2006 in a large private practice using a single IVF laboratory. The patients underwent standard protocols for controlled ovarian hyperstimulation and embryology parameters. The main outcome measure was clinical pregnancy rate. RESULTS: A total of 2167 fresh, non-donor IVF cycles were queried, but to minimize bias, only the first treatment cycle for each patient was analyzed (n = 1273). The data were examined by multiple regression models that included BMI and Age as main effects plus a BMI x Age interaction. When examined as a main effect, BMI did not appear to have a major effect on IVF outcome, but there was a significant BMI x Age interaction. At younger ages, a high BMI had a pronounced negative influence on fertility, but this effect diminished as the patient age increased. Clinical pregnancy rates decreased with increasing BMI and increasing Age. CONCLUSIONS: In younger patients undergoing IVF, BMI has a significant negative impact on fertility that diminishes as patients reach their mid thirties. After Age 36, BMI has a minimal impact on fertility.

EXPLANATION AND SUMMARY OF FINDINGS:

Body mass index (BMI) is a measure of a person’s weight status.  BMI is calculated using a person’s weight and height [weight (in kilograms)/height (in meters)2].  The BMI number obtained (see link to BMI calculator below), determines if a given person is in the underweight, normal weight, overweight, obese, or morbidly obese category.  As a premise to the study, the authors point out that there is an obesity epidemic in the USA, with up to 40% of adult women being obese or morbidly obese.  Furthermore, the authors state that obesity has been linked to infertility and poor reproductive outcome (maternal complications in pregnancy such as miscarriage, gestational diabetes, pregnancy-induced hypertension...).  The authors add that the effect of obesity on IVF outcome is controversial, with some studies suggesting a decrease in pregnancy and live birth (delivery) rates, while others have shown no difference.  In the present study, the authors divided 1272 women undergoing IVF into 4 weight status categories based on BMI (underweight, normal, overweight, or obese).   The average age of patients in the study was 34.4 years.  Using a statistical model, the authors evaluated IVF outcome (response to hormone stimulation, number of eggs retrieved, pregnancy and live birth rates...) as a function of BMI (in other words, they wanted to see if a person’s BMI affects any of these parameters).  What they found was thatBMI (weight status) alone does not seem to affect IVF outcome.  However, the authors did find that when BMI (weight status) and age are evaluated together (BMI x age), IVF outcome varies, with higher BMI at younger age having a negative effect on IVF results, which is no longer seen in older reproductive age (over 36 years of age).  The authors conclude that weight status is an important factor in IVF success in younger patients, while age is a more dominant factor in IVF success than weight status in older women (over 36 years old).

 WHAT DR. MOR THINKS:  
   
Maintaining a balanced healthy lifestyle is important.  Routine exercise, combined with a balanced diet, is essential for your general and reproductive health.  If you can, strive towards a normal BMI (18.5-24.9).  Doing so from a young age will result in better reproductive health and a reduction in risk for many medical problems.  Set yourself realistic goals for childbearing.  If you are young and overweight or obese, delaying childbearing for several months is appropriate, provided you begin a regimented weight loss program, until your targeted BMI is reached.  If you are over the age of 35, delaying childbearing may not be a good idea irrespective of your weight status.  In such cases, attempting to get pregnant should be combined with a weight loss program.
The CaliforniaCenter for Reproductive Health can help you in achieving your weight and reproductive goals.  Please contact us for additional information.

Centers for Disease Control BMI calculator:
www.cdc.gov