Becoming a surrogate is not a cup of tea for everyone. It’s a serious commitment involving time, emotions and physical stress. Only a truly compassionate woman who has experienced motherhood herself can embark on this life-changing journey. However, just willing to become a surrogate is not enough to walk this path. A surrogate mother has to be healthy and meet certain criteria to be considered ideal for this role. One of these criteria is having a healthy BMI.
Why the criteria and what’s with BMI?
Almost all surrogacy contracts (especially those done by the agencies) mandates that the surrogate meet some basic requirements. While these requirements vary case to case, it looks something like this:
- Age between 21-37 years
- Have a BMI (body mass index) within the range of 18 to 32
- Has given birth to a baby of her own
- Have no prior history of major complications during previous pregnancies
- Must not be a smoker
- No prior record of drug abuse
- Do not have criminal background
- Be a citizen or a permanent resident of the country

Now, BMI remains a key factor when considering a surrogate candidate. You may already know the reason behind this.
BMI is directly related to body weight and shows the overall picture of our heath. Here’s what different BMI categories indicate:
- BMI lower than 18.5 = Underweight
- BMI between 18.5 and 24.9 = Normal
- BMI between 25.0 and 29.9 = Overweight
- BMI over 30.0 = Obese
An underweight category indicates that the person is not consuming enough calories while an overweight/obese category implies the perosn is consuming more calories than he/she is spending up.
Why Low BMI is a Red Flag for To-be-Surrogates
A woman with a low BMI or in the underweight category means at risk of certain complications. The primary concern here is increased chances of preterm birth and the risk of a Small Gestational Age Baby.
Being underweight also means that the person might be suffering from deficiency of important micro and macro elements in her body. These elements are very important for the hormone levels which in turn impact various physical changes during a pregnancy. A nutrient deficiency also implies that the baby won’t get the adequate levels of nutrients while gestating.
These factors can put both the mother and the baby in danger which is the last thing expected in a surrogacy journey.
How Does a High BMI Impact a Surrogate’s Pregnancy?
A higher BMI also exposes the surrogate and the baby to several risk factors.
For example, a higher BMI category can lead to complications during surrogate pregnancy such as:
- Difficulties getting pregnant
- High blood pressure, preeclampsia, blood clotting
- Being pregnant past the due date
- Difficulties during labor
- Longer postpartum hospital stay
- Longer postpartum recovery
- Increase chances of cesarean-section
- Miscarriage or stillbirth/pre-term birth
- Increase chances of infections
- Obstructive sleep apnea
- Gestational Diabetes
- Postpartum hemorrhage
A gestational diabetes is where the pregnant woman develops diabetes during pregnancy. This can increase a woman’s risk of developing type 2 diabetes. When gestational diabetes occurs, low blood sugar may develop in the unborn baby. In turn, the woman and the baby are at risk of certain complications. A BMI above 35 (class II obesity) may increase the amount of time needed to get pregnant by100%, while being underweight (BMI below 19) can increase the timeline by 400%.
Gestational hypertension is another risk that could be very concerning during surrogate pregnancy. If not treated properly, gestational hypertension could lead to preeclampsia, which is another serious complication. Moreover, gestational carriers undergo medication courses in order to prepare their body for IVF embryo transfer and pregnancy. The medical protocol is usually prescribed and overseen by the intended parents’ chosen IVF clinic.
It is evident that IVF candidates with a very high BMI do not respond well to the medication. This can lead to a canceled or failed IVF cycle or take more attempts to conceive. Since surrogacy is already an emotionally demanding process, such scenarios can be very frustrating for the intended parents and all the parties involved.
So, How Do You Find Out Your BMI?
Calculating your BMi is pretty simple. You just need to know your weight, height and have a calculator by your side. Here is the formula:
Imperial system:
BMI = (703 x weight in lbs)/ (height in inches x height in inches)
Metric system:
BMi = weight in Kg/(height in meter x height in meter)
Example: If a surrogate weighs 130 lbs (~59 kg) and is 5ft 6 (~1.70m) inches tall, she would have a BMI of:
BMI = (703 X 130)/(66 X 66)
= (91,390)/(4,356)
= 20.98
OR
= 59/(1.70 x 1.70)
= 20.41 (errors due to unit conversion)

You could also use many resources available on the internet to find your BMI, such as the CDC provided BMI calculator.
What can be done to lower your BMI
While a very low or very high BMI is an obstacle for becoming a surrogate, it can be changed by resorting to a healthier lifestyle.
Consult your physician or check with a registered dietician about lifestyle changes, adopting a healthy diet and doing effective exercise.
Conclusion
There are many requirements you need to meet to become a surrogate and a healthy BMI is a key one. A very high or very low BMI can get you and the baby into several risks.
Chances are, your surrogacy agency will carefully screen your physical parameters before accepting your application. If your BMI is off the chart and is preventing you from becoming a surrogate, you should try lifestyle changes to get back in shape.
Also read: Things You Need to Keep in Mind If You are Planning on Breastfeeding Your Baby