Increased Weight Decreases Success of IVF

Posted on February 9, 2015 by Inception Fertility

In the recent past, more than one research team has reached similar conclusions: A higher body mass index (BMI) leads to lower fertility treatment success rates. Reporting at the 70th Annual Meeting of the American Society for Reproductive Medicine (ASRM), the researchers presented findings from three different studies.1

One donor, several recipients.

  • 63 percent had a BMI of less than 25
  • 24 percent had a BMI between 25 and 30
  • 8 percent had a BMI between 30 and 35
  • 5 percent had a BMI greater than 35

Controlling for other factors such as age and number of embryos transferred, the researchers found that a higher BMI was linked with a lower live birth rate. Those with higher BMIs saw the greatest impact. A BMI greater than 35 translated to a 21 percent lower live birth rate.

Donor egg cycles. Also reporting on donor egg cycles—but not comparing donations from a single donor—investigators at Duke University Medical Center used data from the Society for Assisted Reproductive Technologies (SART) reporting system during the years from 2008 to 2010. 1 In recipients with a BMI less than 25, the live birth rate was more than 50 percent. That rate dropped by 10 percent in those with a BMI between 40 and 45.

The patients’ own eggs. The same team of Duke researchers also looked at IVF cycles—between 2008 and 2010—where women used their own eggs. The effect was similar: Birth rates ranged from 31 percent in patients who had a BMI under 25 to 21 percent in those with a BMI over 50.

Although links between BMI and in vitro fertilization (IVF) outcomes have been previously known, these studies help expand our understanding about the importance of weight management in fertility treatment.

Other impacts of obesity. On the heels of these reports come findings that tie maternal obesity to greater odds of having a baby with kidney and urinary tract birth defects. The findings were presented at the 2014 Annual Meeting of the American Society of Nephrology. Prior research has linked maternal obesity to other health problems including newborn heart or neural tube defects.2

In addition, a recent population-based cohort study of 1.8 million singleton infants showed that infant mortality rates at least doubled in women with BMIs of 35 or greater compared to normal weight women.3 Although present, the risks were not as high in women who were overweight, but not obese; the risks increased with increasing BMI.

During pregnancy, the obese mother’s risks increase as well, and include high blood pressure, preeclampsia (which can lead to stroke or death), and gestational diabetes. 4

According to the American College of Obstetrics and Gynecologists (ACOG), about eight percent of reproductive-aged women are extremely obese.

Why weight? How extra weight impacts pregnancies and birth outcomes isn’t yet fully known. However, researchers do know that extra weight can influence a body’s hormonal or biochemical milieu. It alters the metabolism of carbohydrates and fats, for example, which can lead to insulin resistance—a condition that makes it harder for glucose to enter cells. Insulin resistance can also lead to diabetes. Changes like these may create a uterine environment that’s less “friendly” for eggs or embryos, making healthy development more challenging.4

Reducing your risks. It’s clear to see why getting your weight to a healthy range is a top priority before becoming pregnant. It can help prevent complications and is even more important if you’ve experienced complications with a previous pregnancy.

Even if you’re successful getting pregnant and carrying your baby to term, research suggests that overweight mothers my inadvertently program their babies in utero to become overweight themselves.4

If you have trouble getting off all the weight you’d like to before pregnancy, you can make a difference by containing your weight gain during pregnancy. You may find it helpful to join a support group—maybe one made up of other women who are facing similar challenges. Also, talk with your doctor about dietary changes as well as safe ways to incorporate more exercise into your daily routine. Small changes can make a big difference.


  1. ASRM: Weight Impacts Success of Donor Egg Cycles. 10-20-14.
  2. MedlinePlus: Kidney, Urinary Birth Defects Tied to Obesity in Moms-to-Be.
  3. Johansson, Stefan et al. Maternal Overweight and Obesity in Early Pregnancy and Risk of Infant Mortality: a Population Based Cohort Study in Sweden. BMJ?: British Medical Journal 349 (2014): g6572. PMC. Web. 10 Dec. 2014.
  4. ACOG: Obesity and Pregnancy FAQs. June 2013.
  5. Kasim K, Roshdy A. Body Mass Index and Pregnancy Outcome after Assisted Reproduction Treatment. International Journal of Reproductive Medicine. Vol. 2014, Article ID 257974, 5 pages, 2014. doi:10.1155/2014/257974.

- The PFC Team

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