Becoming a surrogate is an incredibly beautiful and selfless act. It’s an opportunity for you to give the gift of new life to another family, but it’s also a lot of responsibility. As a surrogate, you’re carrying the hopes and dreams of the Intended Parents who have often been through a long process making this pregnancy happen, so they deserve the very best chances for a successful outcome.

Women who have decided to become surrogates are sometimes surprised to face stringent health criteria, particularly when it comes to their height to weight ratio. And while being overweight does not necessarily disqualify you as a surrogate, a Body Mass Index (BMI) of 33 or less is required by most fertility clinics. You can determine your BMI by dividing your weight in kilograms by your height in meters squared or using our BMI calculator

Scientific research has shown that your BMI can provide an accurate indication of your overall health and whether you might be at risk of any health issues.  

This is extremely important for getting pregnant, especially with third-party reproductive technology. And it’s even more important when you’re carrying someone else’s baby! 

A BMI between 18.5 – 24.9 is considered healthy and indicates a normal height to weight ratio. A BMI of 26 or 27 suggests that you are about 20 percent overweight, which can carry moderate health risks. A BMI of 30 and higher is considered obese. 

Here’s an overview of why a healthy BMI is important for all women who are considering surrogacy.

Health risks associated with high BMI

In a nutshell—the higher your BMI, the greater your risk of developing health problems. In most cases, it means you have a higher percentage of body fat, which may increase your risk of cardiovascular disease, high blood pressure, and high cholesterol. Other issues can include sleep apnea, hypertension, arthritis, diabetes, gestational diabetes, and many forms of cancer.

Obviously, these are serious conditions that can harm not only the health of your surrobaby, they also put your own health at risk. But there are even more problems associated with pregnancy when your BMI is high. 

Being overweight or obese can affect nearly all the components of the reproductive system, from the function of your eggs to the quality of embryos and even your uterus itself. Higher body fat is also associated with an increased risk of miscarriage in the first trimester and recurrent miscarriages. 

Even women trying to conceive naturally have a much lower rate of success if their BMI is over 29. 

Lower IVF success rates

Several studies have shown that being obese can reduce the success of IVF outcomes. A high BMI is linked to a lower fertility rate, usually due to problems with ovulation. It can also lead to lower success rates with fertility treatments, including IVF, along with a higher rate of miscarriage.

One particular study from the American Society for Reproductive Medicine found a proven link between weight and infertility. Women of normal weight who underwent IVF had an implantation rate of 24%, while the rate for overweight women was only 15%. This finding was backed by previous studies that have also suggested overweight women require higher doses of fertility medications, are less likely to get pregnant and have higher miscarriage rates.

Lower embryo implantation rates

Obesity reduces endometrial receptivity. Women with higher BMIs are found to have significantly lower implantation, pregnancy, and live births rates, along with a substantially higher rate of miscarriage compared to women of healthy BMI. 

A large European study that investigated women undergoing egg donation treatment found that being obese reduces the embryo implantation rate, which can compromise the rate of conception. The study authors concluded that high body fat reduces uterine receptivity during embryo implantation, which means the implantation is less likely to be successful. 

As a result, they advised that a healthy weight is crucial for anyone trying to get pregnant, whether through natural or third-party reproduction. 

Lower response to medication used to regulate ovulation

Being overweight or obese can reduce your body’s response to fertility treatment. A higher weight has been shown to decrease your response to the medication used to induce ovulation, which is a big problem for a surrogate. Obese women undergoing IVF often require higher doses of gonadotrophins (FSH), respond poorly to ovarian stimulation, and have fewer eggs (oocytes) harvested. 

Though dosing changes could improve chances for a successful pregnancy, high BMI is also associated with poor-quality embryos and a lower rate of fertilization.

Greater need for carefully measured dosing 

The rate at which the body clears drugs increases with body size, which means people with higher body mass have different dosing requirements. It can be challenging to calculate the proper dosage of fertility drugs because most drug dosages are based on data from women of average weight.

Having a higher BMI can also place a more significant strain on your liver and kidneys, so they may not function as efficiently when processing and eliminating fertility drugs. This pushes your risk of medical issues up even higher. 

Multiple pregnancies

Multiple pregnancies are much more likely with IVF procedures due to the number of embryos implanted. In women of healthy BMI, the risk of complications carrying twins or triplets is already increased above that of a singleton, but this risk is even greater if the woman has a high BMI. 

An enjoyable surrogacy experience

You can see why a healthy BMI is so crucial for a healthy pregnancy! Carrying a baby is quite a task for a woman’s body, and a growing fetus needs you to be in the best health possible. 

At Family Source, we want all of our surrogates to enjoy their surrogacy from preconception right through to birth and beyond. A healthy BMI means you’re much more likely to sail through your pregnancy and simply look forward to creating a little life! 

Staci Swiderski, CEO and owner of Family Source Consultants has been involved in the field of reproductive medicine since 2002. Staci has vigorously grown the comprehensive egg donation and gestational surrogacy agency to become a worldwide leader in the third-party reproduction field. Staci is a former intended parent herself. She and her husband welcomed their son via gestational surrogacy in 2005. Additionally, Staci had the experience of assisting an infertile couple (AKA Recipient Parents) build their family through her efforts as an egg donor, with her donation resulting in the births of their son and daughter.