Having a body mass index (BMI) outside of the healthy range can affect your chances of conceiving through IVF. Understand the reasons behind IVF BMI limits, and how you can optimise your BMI to improve fertility.
What is BMI?
Body Mass Index (BMI) is a measure of body fat based on your height and weight. It serves as a general indicator of healthy weight ranges. A BMI between 18.5-24.9 is considered normal, indicating a healthy weight. If your BMI falls below 18.5, you are considered underweight; a BMI between 25-29.9 is classified as overweight, and a BMI of 30 or above is considered obese. Understanding where you stand can help you take actionable steps towards a healthier lifestyle and improved fertility. The NHS has a handy tool to help you calculate your BMI based on your height and weight.
How can your BMI affect your chances of successful IVF?
Your BMI can significantly impact your chances of successful IVF. Studies show that women with increased BMI have worse IVF outcomes than women with a normal BMI.
Both underweight and overweight conditions can pose challenges. A high BMI, specifically over 30, is often linked to lower egg quality and higher risks of implantation failure. Excess body fat can cause hormonal imbalances and ovulation issues, reducing the likelihood of conception. Additionally, a high BMI increases the risk of complications during pregnancy, such as gestational diabetes, preeclampsia, and hypertension, which can affect both mother and baby.
On the other hand, a low BMI, below 19, can also disrupt hormonal balance and lead to irregular menstrual cycles, making it difficult to conceive. It can result in poor egg quality and insufficient endometrial lining development, crucial for implantation.
Achieving a BMI within the healthy range of 20-25 optimises your fertility by ensuring balanced hormones, regular ovulation, and a supportive environment for pregnancy.
Age also plays a role, with one study revealing that BMI can greatly affect the pregnancy outcomes of women aged 30–38 years specifically.
Why are there often IVF restrictions for people with a high BMI?
IVF restrictions for people with a high BMI are often in place due to the associated lower success rates and increased health risks. For NHS-funded IVF, BMI limits typically range between 19-30. This is because a higher BMI can lead to complications such as reduced egg quality, implantation failure, and higher miscarriage rates. Moreover, obesity can contribute to hormonal imbalances and ovulation issues, further diminishing the chances of successful conception.
Additionally, women with a high BMI are at a greater risk of developing pregnancy-related complications like gestational diabetes, preeclampsia, and hypertension. These risks not only affect the mother’s health but also the wellbeing of the baby. Private clinics may offer more flexibility, but many still recommend weight loss for those with a BMI over 35 before starting treatment.
By addressing weight issues and striving for a healthier BMI, you can improve your fertility and overall health, making your IVF journey safer and more successful.
Is there an optimal BMI when trying to conceive?
Most fertility experts agree that maintaining an optimal BMI between 19-25 offers the best chances for IVF success and healthy pregnancy. This BMI range supports balanced hormone levels, regular ovulation, and overall reproductive health, minimising the risks associated with both underweight and overweight conditions. Studies suggest that both very low and very high BMI levels are associated with a higher risk of infertility. Research has also found that women who are obese or overweight take longer to conceive and have a higher risk of fertility issues compared to women with a normal BMI. Achieving and maintaining this BMI can significantly reduce the likelihood of complications such as ovulation disorders, hormonal imbalances, and poor egg quality.
Being within this range also lowers the risk of pregnancy-related issues like gestational diabetes and hypertension, creating a healthier environment for both mother and baby. If your BMI falls outside this range, making gradual lifestyle changes through a balanced diet and regular exercise can help. Remember, every step you take towards a healthier BMI is a step towards optimising your fertility and enhancing your chances of a successful IVF journey.
Can a low BMI also affect fertility?
Studies show that having a low BMI, specifically below 19, can significantly impact fertility due to several physiological disruptions. Low body weight often correlates with reduced levels of essential reproductive hormones, such as oestrogen and progesterone, leading to irregular or absent menstrual cycles. This hormonal imbalance can prevent ovulation, making it difficult to conceive. A low BMI can also result in poor endometrial lining development, which is crucial for the implantation of a fertilised egg. Women with low BMI may also experience nutritional deficiencies that negatively affect egg quality, further reducing the chances of a successful pregnancy. Plus, the body’s response to low energy availability can lead to a condition known as hypothalamic amenorrhea, where the brain signals the body to conserve energy, halting reproductive functions. Maintaining a BMI within the healthy range can help ensure regular ovulation, a well-nourished endometrium, and overall better fertility outcomes.
How can you improve your BMI and overall health for IVF treatment?
Making lifestyle changes to reach a healthier BMI before fertility treatment can significantly increase your chances of success.
Maintain a healthy diet, reducing intake of processed foods
Maintaining a healthy diet is essential for improving your BMI and overall health, especially when preparing for IVF treatment. Focus on consuming nutrient-dense foods like vegetables, fruits, lean proteins, and whole grains while reducing the intake of processed foods high in fats and sugars.
Processed foods and those with saturated and trans-fatty acids can contribute to weight gain and other health issues that may affect fertility. Whereas opting for low glycemic index (GI) carbohydrates can help keep blood sugar levels stable. Studies show both insulin sensitivity and glucose metabolism can significantly affect ovulation and female fertility. Low GI foods, such as whole grains, legumes, and non-starchy vegetables, provide sustained energy and support overall metabolic health, creating a favourable environment for conception. Read more about how to create a healthy fertility diet plan with our blog.
Limit alcohol and caffeine consumption
Limiting alcohol consumption is crucial for improving your BMI and overall health, especially when preparing for IVF, as alcohol contains a lot of calories. Excessive alcohol intake can impair fertility in both men and women, with studies showing consumption of as few as four alcoholic drinks per week is associated with a decrease in IVF birth rate.
To enhance your chances of conceiving, reduce alcoholic beverages and cut back on caffeine from coffee, cola, and energy drinks, as there are some suggestions that high levels of caffeine may be detrimental. Instead, opt for water, herbal teas, and other non-caffeinated options. These changes not only support a healthier BMI but also create a more balanced and supportive environment for your fertility journey. Discover more about the impact of drinking when trying to conceive with our guide.
Stick to a regular exercise routine
Sticking to a regular exercise routine is vital for achieving an optimal BMI and enhancing your overall health, especially when preparing for IVF. Engaging in moderate activities like brisk walking, swimming, or cycling helps you manage weight effectively and boosts your fitness levels. Regular exercise can improve cardiovascular health, reduce stress, and balance hormones. These benefits collectively create a healthier environment for conception. Regular exercise not only supports your fertility journey but also empowers you to take control of your wellbeing, making every step towards IVF success more achievable and fulfilling. It’s best to keep to low-impact exercise, especially if undergoing IVF treatment.
Start taking the right fertility supplements
If you’re considering IVF, the quality of the eggs is of utmost importance as it significantly influences the potential success of conception. To enhance egg quality, incorporating specific female fertility supplements into your daily habits could be beneficial. Essential supplements like folic acid and vitamin D should be started in preparation for IVF or conceiving naturally, and should be continued for optimal results.
Impryl is a supplement designed to promote egg quality and overall reproductive health. It’s formulated with nutrients backed by research that support your body’s metabolic balance, creating an ideal environment for egg development and offering protection against DNA damage. This helps to ensure the highest quality eggs are produced. Avoid taking multiple different multivitamins while taking Impryl, as many of these can potentially upset the delicate metabolic balance required for optimal development of eggs and sperm.
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Regular self-care through diet, exercise and research-backed supplements gives you the best chances of optimising your BMI for successful IVF treatment while also nurturing your overall wellbeing. By taking proactive steps now, you can take control of your fertility journey and give yourself the healthiest possible odds of conception.
References
Liu, X., Shi, S., Sun, J. et al. The influence of male and female overweight/obesity on IVF outcomes: a cohort study based on registration in Western China. Reprod Health 20, 3 (2023). https://doi.org/10.1186/s12978-022-01558-9
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