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How Weight Can Affect Fertility and IVF Treatment Success in Women

weight and infertility in women
Weight can have a significant impact on all aspects of your mental and physical health, particularly when it comes to fertility. This article explains how obesity and being underweight can affect infertility and IVF treatment and how you can achieve and maintain a healthy weight that’s conducive to achieving a successful full-term pregnancy.

How Being Overweight or Obese Affects Your Fertility

Before delving into the pregnancy and fertility complications associated with obesity, it’s important to have an understanding of what it means to be overweight or obese. Body Mass Index (BMI) is the main formula used to calculate your weight in relation to your height.

Although there’s some controversy in terms of whether BMI is a completely accurate indication of good health, it’s still a helpful tool that can contribute to the much bigger picture of a patient’s health. According to the World Health Organization (WHO), a healthy BMI is anywhere between 18.5 to 24.5. A BMI that ranges between 25.0 to 29.9 is considered overweight. Patients with a BMI rating of over 30.0 or higher are considered to be obese.

Worldwide obesity rates have been on the rise for decades with approximately 40% of the world’s adult population being classified as obese. Moreover, Statistics Canada has reported that approximately 62% of Canadian adults are either overweight or obese.

Unfortunately, overweight or obese adults—both men and women—can have a much harder time successfully achieving full-term pregnancy and live birth as a direct result. Here’s how being overweight or obese can negatively impact fertility including infertility and IVF treatment.

Impact on Hormone Levels

Obesity can lead to anovulation, a condition that prevents the ovaries from producing a mature follicle and releasing the egg. Classified as an endocrine organ, adipose tissue (also known as body fat) produces a variety of different hormones. Estrogen and leptin are two of the hormones produced by fat cells. Overproduction of these hormones can cause abnormalities in the menstrual cycle and lead to anovulation.

Obesity can also increase the risk of miscarriage and poor neonatal and maternal pregnancy results. It increases health risks for procedures that require anesthesia, including IVF treatment. Procedures that require anesthesia or any form of sedation are therefore reserved for patients with a BMI of 40 and under.

Increase in Insulin Resistance

Obesity increases insulin resistance due to a pronounced lack of tissue response. This makes it extremely difficult and nearly impossible for the cells in the body to properly absorb sugar, which can lead to high or low blood sugar levels. In addition to causing type 2 diabetes in adults, high blood sugar levels can hinder ovulation and embryo development. High blood sugar levels can also weaken the quality of eggs produced and it’s also linked to cardiovascular disease.

Affects Your Partner’s Fertility

Studies have shown that obese or overweight men have a higher chance of being infertile than men of a healthy weight. Obesity in men has been linked to lower testicular function, low motility sperm, and lower testosterone levels. As a result, obese or overweight men are less likely to produce viable enough sperm that will result in a positive IVF treatment or infertility treatment outcome. To increase the chances of achieving a successful and healthy full-term pregnancy, it’s important that both partners are in good physical health.

Obesity Reduces Chances of Conception

Obesity can have a severely negative impact on the success of IVF treatment. Obese patients require significantly higher doses of medication that’s required to stimulate the ovaries. Yet, the chances of a successful embryo implantation are significantly lower and the chances of suffering a miscarriage are higher.

How Being Underweight Affects Your Fertility

What does it mean to be underweight? Having a BMI of 18.5 or lower classifies you as being underweight. In addition to posing potentially serious health risks, being underweight can be just as detrimental to the success of infertility and IVF treatments as being overweight or obese.

Women with a low BMI can suffer from abnormal menstrual cycles, irregular ovulation, or they may not menstruate at all due to extremely low hormonal production. Here are a few important factors to take into consideration if you’re underweight and trying to get pregnant.

Lifestyle Modifications

Making a few minor lifestyle modifications that aid in reaching a healthy weight can help increase your chances of achieving a successful full-term pregnancy either naturally or through infertility treatment and counselling. Pregnancy can place a huge toll on your body between all of the hormonal changes and the need to support a growing fetus. With that in mind, it’s important that you do everything in your power to maintain good health and achieve a healthy body weight before trying to get pregnant.

Impact on Fertility and Hormones

Just like being overweight or obese, being underweight can also cause severe hormonal changes in women that can make it harder or impossible to achieve a pregnancy. Underweight women are at a higher risk of having reduced estrogen levels. Combined with irregular menstrual cycles and the inability to ovulate, this can prolong the conception process by a year or longer.

Understandably, some women just have naturally fast metabolisms and have a hard time gaining weight. Other women may suffer from body image issues such as dysmorphia or eating disorders that may prevent them from gaining weight. If this is the case, then it’s important to consult with your doctor immediately, so that they can map out a feasible health plan to get you to a healthy weight to conceive a child.

Increased Chance of Preterm Birth

What is preterm birth? Preterm birth occurs when the baby is born prematurely or before it’s fully developed. Also known as premature birth, preterm birth typically occurs any time before the 37 week mark (9 months) of pregnancy. At this point, the baby isn’t fully developed yet and will most likely require significant medical attention. There are three types of preterm birth that are linked to underweight women getting pregnant:
  • Extremely preterm birth, which occurs after less than 28 weeks
  • Very preterm, which occurs between the 28- to 32-week mark
  • Moderate to late preterm which occurs between 32-37 weeks

Infertility Counselling and Treatment at ONE Fertility Kitchener Waterloo

At our fertility clinic, we have a fairly simply philosophy when it comes to providing quality infertility counselling to our patients. We use a compassionate evidence-based medical approach to create a custom-tailored treatment plan that suits your specific needs. ONE Fertility Kitchener Waterloo takes on a patient-focused approach to providing excellent infertility treatment and care. Contact us today to learn more.


4271 King St East, Suite 200
Kitchener, ON
N2P 2X7

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