Home Health/Medical Dr. Payne on BMI and IVF

Dr. Payne on BMI and IVF

Q & A with Dr. John Frederick Payne,  MD 

Reproductive Endocrinologist & PREG Partner

Discusses BMI and IVF

Why is BMI so important in terms of getting pregnant via IVF?

The prevalence of obesity is a worldwide epidemic. In the U.S. almost ⅔ of women and ¾’s of men are overweight or obese.  And nearly 50% of women of reproductive age are obese, or overweight.  So, it’s a big problem in America and obviously, that means it’s a big problem for the patients we are seeing for reproduction.

We know obesity increases the regular risk for health issues like hypertension, diabetes, heart disease, sleep apnea, respiratory problems, osteoarthritis, and cancer. Obese people, in general, have an elevated mortality rate over individuals of normal weight.  The definition of obesity is the degree of body fat that a person has, which is strongly associated with insulin resistance, and categorized by Body Mass Index or BMI.

Explain the Importance of BMI

A normal BMI is 19-24, BMI less than 19 is considered underweight, and a BMI of 20-25 is considered overweight. A BMI of greater than 30 places you in one of three categories of obesity, Category 1 BMI 30-35, Category 2 BMI 35-40, and Category 3 BMI over 40.  Regarding reproduction, many underweight or overweight and obese women will have no problem getting pregnant.  But others will have a problem conceiving and most often it is due to ovulation problems.  Thin women could have an eating disorder that would require medical treatment resulting in natural ovulation.  Women with BMI in the obese range can have irregular menstrual cycles and not be ovulating.  However, even if the obese woman has normal ovulation cycles, they will still have a lower pregnancy rate than a normal-weight woman.  So, ovulation or not ovulating is not the only problem for overweight or obese women in conceiving and delivering.   

Being overweight or obese often causes ovulatory dysfunction.  Many times, both the ovulatory function and pregnancy chances will improve after the weight loss, so we are always going to encourage weight loss.  But weight loss will not always result in pregnancy, but weight loss should help reduce the other medical risks mentioned earlier.  In obese women undergoing fertility treatments, obesity is associated with higher doses of medications being required to induce ovulation or stimulate the ovaries for IVF.  This is correlated with fewer mature follicles and a decreased chance for ovulation.  Similar doses of fertility medicine just do not seem to reach and affect the ovarian follicles in the same manner as it would in a thinner person.  Because obesity impairs the ovarian responsiveness to the natural stimulation, it typically takes an increased duration and increased amount of the medicine to be administered, resulting in increased costs (of these expensive fertility medications). Sometimes obese women can have a higher number of canceled cycles and a decreased number of eggs retrieved.  

Is PCOS a factor in overweight patients?

PCOS women will many times have a much higher number of eggs retrieved because of the PCOS. An obese woman with regular menstrual cycles still can experience a decreased chance to get pregnant every month as compared to normal-weight women.  There is an association between PCOS and obesity with most women with PCOS being obese. PCOS affects about 8-10% of women with infertility usually causing oligoovulation or anovulation.  But not all women with PCOS are overweight and many women will have signs of insulin resistance. We treat women with PCOS through a combination of a low-calorie diet, exercise, trying to have weight loss, and also metformin if they have some resistance or pre-diabetes. Metformin works synergistically with the ovulation induction medicines such as Clomid or Letrozole and we can help most women ovulate. 

Why Is BMI so significant?

There have been studies that clearly show obesity lowers pregnancy rates. One study reported a 4% lower response pregnancy rate per a point increase in BMI, so every point your BMI goes up your natural conception rate goes down by 4% a month in this one study.  Even with IVF which has the highest chance for pregnancy, obese women have a reduced chance of live birth compared to normal-weight women.  The success rate can be maybe 12% to 25% lower in obese patients compared to normal BMI’s less than 25.  Some of those IVF studies found that there is a 2% decrease in the live birth rate for every 1 unit increase in BMI.

So a higher BMI, or obesity really affects pregnancy chances?

Yes, this is why we try to encourage weight loss.  Obesity also alters the egg morphology and can reduce fertilization rates in some but not all and can impair embryo quality.  So it’s not just about the lower response you might observe sometimes, but the eggs aren’t as good, which leads to a lower pregnancy rate.   Studies have found the decreased pregnancy rate in obese women that did IVF using their own egg can be overcome by using donor eggs.  The oocyte quality is a primary reason obese women get pregnant at a lower rate, but maybe not the only reason.  There is also some data that shows obesity can alter the endometrial function so that implantation of embryos after an embryo transfer is lower.   It can be harder to get pregnant because the endometrium is not as receptive. Obesity is also linked to an increase in miscarriages.  

Obesity is strongly associated with pregnancy and prenatal complications including gestational diabetes, preeclampsia, stillbirth, cesarean delivery, shoulder dystocia, fetal distress, early prenatal death, as well as, small and large for gestational infants.  Women that conceive via IVF are also at risk for preeclampsia, gestational diabetes, cesarean delivery, and pre-term delivery.  

In men with obesity, there can be changes in testosterone levels and other hormones that are important for reproduction, leading to issues such as low sperm count and low sperm motility as compared to normal-weight men.  

Management of Obesity?

Lifestyle modification is basically combining diet, exercise, and behavioral modification. To have weight loss, you must take in fewer calories and burn more calories one way or another.  There are medical treatments for weight loss and there is bariatric surgery. There were over 100,000 bariatric procedures in the U.S. of 340,000 bariatric procedures worldwide in 2011. Bariatric surgery is probably the most effective way for women to lose weight with a BMI of over 40.  But after bariatric surgery, women are recommended to delay pregnancy for at least a year if not longer during the rapid weight loss phase.  The problem with postponing pregnancy to a better pre-conceptual weight is trying to balance the risk of declining fertility with advancing age.  What might be ok for younger women might be inappropriate for older women who do not have the time needed for proper weight loss. But for all women, we would prefer that they are as healthy as they can be when they are trying to conceive and are going through fertility treatment.  At the end of the day, we want a healthy mother and a healthy baby, so the weight loss is going to optimize that.  But sometimes due to advancing age or diminished ovarian reserve we must move forward with fertility treatment if we want to have any chance for a woman to use her own eggs (rather than an egg donor).  

Are there BMI limits for IVF?

With IVF our BMI cutoff is 45 due to the inability to safely administer the anesthesia required for the IVF egg retrieval under IV sedation. Some women with a lower BMI may not be a good candidate for IV anesthesia due to a compromised airway or other medical comorbidities.   Obesity can also cause difficulty with ovarian visualization using the transvaginal ultrasound making ovarian stimulation monitoring difficult and transvaginal ultrasound-guided egg retrieval impossible. In those cases, we may not be able to perform IVF until weight loss occurs.

In summary, we would love for people to all be a normal BMI including our infertility patients, but the closer to normal BMI patients are when they present for infertility evaluation and treatment, the better their chances are for getting pregnant, staying pregnant, and having a healthy conclusion to their pregnancy. Many obese men and women are fertile, but obesity in women is associated with ovulatory dysfunction, reduced ovarian responsiveness to ovulation induction medicines, altered egg, and endometrial functions, and lower birth rates.  Obese women are at an increased risk of developing maternal and fetal complications during pregnancy.  Obesity in men may be associated with impaired reproductive function. Lifestyle modifications in both men and women are the first line in treatment for obesity followed by medical therapy and then bariatric surgery. Bariatric surgery works best if BMI is over 40, but pregnancy should be deferred for at least one year during the rapid weight loss phase.

PREG  has 3 IVF Surgery Centers (Greenville, Columbia & Lowcountry) and a total of 5 offices with satellite offices in Asheville & Spartanburg.

866.725.7734

Images: Unpslash.com

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