During this event, Dr Laura García de Miguel, Medical Director at Clínica Tambre, discussed the effects of BMI on fertility and explained what you can do to improve your outcomes.
Dr García started by introducing Clínica Tambre, where the entire team aims to create a diagnosis to achieve pregnancy for each patient. The team specializes in complex cases, with over 45 years of experience, working with patients from more than 80 countries. They have helped create families with more than 15,000 babies.
Clínica Tambre’s state-of-the-art laboratories and operating theatres use the latest technologies. The team excels in advanced reproductive treatments, including pre-genetic diagnosis, time-lapse monitoring, Fenomatch, and methods to ensure the best donor-to-recipient matches. The team also studies sperm quality with Comet Fertility and ensures correct sample handling with RiWitness. If necessary, the team investigates infections and receptivity using endometrial solutions.
The ideal range is 18.5 to 24.9. Less than 18.5 is underweight, which can cause ovulation problems. Overweight is classified as 25–30, obesity as 30–35, and severe obesity as more than 35. Being overweight or underweight can lead to anovulatory cycles and other impacts on fertility.
Weight matters in fertility because it affects both fertility and pregnancy outcomes. In 2019, 52% of adults in Europe were overweight.
Weight matters in fertility because it affects both fertility and pregnancy outcomes. In 2019, 52% of adults in Europe were overweight. There is always a BMI and fertility connection: if BMI is not in the ideal range, the risk of fertility problems increases. The recommended BMI for higher chances of conception is 18.5 to 24.9. A BMI over 30 can lead to conception difficulties and increased pregnancy risks, including diabetes and high blood pressure.
How does weight impact fertility? Hormonal imbalances due to excess estrogen can block hormone secretion by the hypothalamus and pituitary, leading to irregular or non-ovulatory cycles. It may also increase the risk of polyps and hinder development. Polycystic ovary syndrome (PCOS), common in overweight women, affects ovulation and egg quality.
In men, being overweight can lead to lower sperm quality, reduced quantity, impaired mobility, and affected morphology. This can reduce fertilization rates and embryo quality. Maintaining a healthy BMI in men can improve outcomes in fertility treatments.
For treatments like IVF, being overweight can lower hormonal response. Obesity reduces stimulation effectiveness, even if the ovarian reserve is good. Higher dosages may be needed, but the response to treatment can still be reduced. Obesity increases risks and difficulty during procedures like egg collection and embryo transfer. Outcomes may include lower fertilization rates, fewer high-quality embryos, and reduced implantation rates. Evidence shows that implantation rates are lower in patients with a BMI over 30.
Pregnancy can also be affected by obesity. Maternal complications include increased risks of hypertension and gestational diabetes, as well as a higher likelihood of Caesarean sections, preterm delivery, and perinatal mortality. Babies face higher risks of malformations and high birth weight.
Maintaining a healthy BMI reduces risks and supports better pregnancy outcomes, improving fertility success rates while enhancing overall health and well-being.
A balanced diet and regular exercise are key to maintaining a healthy BMI. This improves ovarian and sperm function, reduces risks, and increases fertility success rates. The weight goal before pregnancy is to maintain a BMI between 18.5 and 24.9. Lifestyle changes such as a balanced diet and physical activity are essential. A healthy BMI can reduce risks and improve the chances of success in achieving pregnancy.
While BMI is not the only factor affecting pregnancy, improving it can significantly increase the likelihood of success.
Most clinics set a BMI rule for IVF, and the limits differ by country. Fertility Clinics Abroad’s guide to BMI limits for IVF reports that “NHS IVF in the UK is funded at a BMI of 19 to 30, private UK clinics usually treat to 35 and some to 40, US clinics set 35 to 45 with hospital units going higher, and no European country except Serbia limits IVF by BMI in law.” The guide also lists which clinics in Spain, Greece, North Cyprus and the Czech Republic assess patients above 35 case by case.
The optimal BMI range is 19 to 24. A BMI of 28 is a bit higher than the optimal range, but not excessively so. If we work in parallel with fertility treatments, as well as improving diet and lifestyle, we can achieve much better outcomes.
Let’s calculate your BMI. With a weight of 76 kilograms and a height of 1.69 meters, your BMI is 26.6. This is close to the normal range. However, if you can incorporate some exercise and reduce your weight slightly, it would be even better.
In our clinic, we wouldn’t delay treatment for a BMI in this range. While weight loss isn’t mandatory, working on improving weight in parallel with treatments, with the help of a dietitian and regular exercise, can prepare you better for the process.
The exact link between BMI and egg quality isn’t entirely clear, but metabolic issues can have an impact. A BMI over 25 isn’t considered a significant concern unless it moves into the obesity range. Obesity, from an endocrinological perspective, can cause hormonal imbalances, leading to increased risks of anovulatory cycles—when periods occur, but ovulation doesn’t happen correctly. This, in turn, reduces the probability of natural conception.
Stimulation dosage during fertility treatments is carefully selected, not just based on ovarian reserve but also weight. For instance, I recently had a young patient with a good AMH level who was overweight. While her ovarian reserve was excellent, her weight was a factor that required adjusting the stimulation dosage.
When BMI is higher, response to stimulation might be less effective, which can reduce the probability of pregnancy. This is particularly relevant in IVF stimulation protocols.
PCOS is indeed frustrating as it’s a leading cause of difficulties in conceiving and often impacts weight. Not all women with PCOS struggle with weight, but many do. You can consult an endocrinologist to explore treatments that regulate glucose and insulin metabolism, such as metformin. Also, consider diets like intermittent fasting, which have shown significant benefits for both weight and overall health.
In more challenging cases, discuss newer medications with an endocrinologist. These include injectable treatments that help reduce appetite and facilitate faster weight loss. Combining these approaches under expert guidance can be very effective.
That is a very intelligent question. Of course, I know that complexity and genetics can differ significantly between populations. For example, I work with African women, and their body structure is very different from Europeans. I am not as strict with these women because I understand their complexity and genetics.
However, I always try to be honest and explain that, if they can reduce weight, change their lifestyle, or do whatever is within their control, it will help improve their chances of pregnancy. The sooner they can make these changes, the better.
Yes, it is important to consider each case individually. At our clinic, we always welcome everyone. Some patients find it extremely frustrating and desperate when they cannot find a clinic to accept their case.
Sometimes we recommend reducing weight before starting treatment, or we may stimulate ovaries and create embryos first. For the transfer, which has the most significant impact on implantation, we might recommend postponing until conditions are more optimal. This way, patients feel they are progressing, which helps maintain motivation to work on lifestyle changes.
It is always important to share your weight and height with your doctor, in addition to information about your ovarian reserve, AMH levels, and antral follicle count. These parameters are essential for selecting the best stimulation treatment plan for you.
In this situation, the challenges may include reduced implantation rates, a higher risk of diabetes, and a higher risk of high blood pressure disorders during pregnancy. That is why it is so important to address BMI and overall health in preparation for treatment.
I am deeply sorry for what you have gone through. If you had a consultation with me, I would explain that weight is not the principal cause of infertility or pregnancy complications in cases like yours. The neonatal asphyxia was a multifactorial issue, unrelated to your weight, and you should discuss it with the medical team that managed your delivery.
Similarly, the miscarriage was caused by chromosomal abnormalities (Trisomy 18), not your weight. However, reducing your BMI from 28 to 25 and working with a clinic in parallel can increase your chances of having a successful pregnancy.
At this stage, the main concern is your age, as it significantly impacts egg quality and fertility outcomes. Working closely with a specialist is essential to optimize your chances.
That is not correct. Reducing weight, if we are overweight, is always welcome as long as it is done under expert supervision. Having blood tests and taking supplements if necessary makes the process safe. Losing weight is not a risk, even during pregnancy. Overweight patients can continue reducing weight during pregnancy as long as they are supervised by a dietician or expert. This is always safe and highly recommended before pregnancy.
Implantation rates are always less probable when BMI is higher than normal. The recommendation is to try to reduce weight, follow a healthy lifestyle, and make lifestyle changes to improve the chances of success.
For patients older than 38, we traditionally use Pergoveris, which works very well. Also, because Menopur is no longer available in Spain, Pergoveris is frequently used. Regarding 6.2 pmol/L (which converts to about 0.8 ng/mL), a dose of 300 units is recommended. Higher dosages, beyond 300 units, do not significantly increase the response or produce more eggs, so 300 units is considered the maximum dosage.
Endometriosis is one of the major causes of infertility. It impacts the quality and quantity of eggs, which affects IVF success. Adenomyosis, on the other hand, affects the walls of the uterus and reduces the implantation rate. For patients with adenomyosis, we need to use specific protocols to reduce its activity and improve the chances of successful implantation.
Losing a significant amount of weight, such as 20–30 kilograms, is not a risk, especially if you are severely obese. It is always safer to reduce weight rather than continue with obesity, which can increase the risk of cardiac diseases, strokes, and other complications. Weight loss, even if significant, is highly recommended for improving overall health and fertility outcomes.
Menopur is produced abroad, and there is currently a legal issue with its production. This is a worldwide situation. Some countries still have access to existing stock, but new production has been halted. It is expected that this situation will be resolved within a year or 2. Menopur remains an excellent medication and is still used in other countries where stock is available.
We recommend tests for liver function, TSH, anaemia, and vitamin levels. These ensure the body is in perfect condition and that weight reduction does not negatively impact overall health.
The question seems to ask about the maximum BMI that is still acceptable. I’ve had many patients unable to reduce their weight. Some patients with a BMI over 38, though not ideal medically, have successfully delivered healthy babies. It’s always a balance between the psychological perspective and helping a woman achieve her dream of starting a family. Each case is individualized, considering other parallel risks or factors.
The ideal BMI for a donor egg transfer is under 25. However, due to the impact of obesity on society, we cannot always restrict this. While a BMI of less than 28 is preferable, it’s crucial not to exceed 32. This too should be personalized, depending on the individual’s overall health.
Obesity can influence the uterine environment, alter progesterone levels, and create an anovulatory environment. These hormonal imbalances reduce implantation chances. If you’re interested, you can contact our clinic for further details or studies on this topic.
Yes, it can be helpful for many patients. From my perspective, obesity is never the sole cause of challenges—it is one of many multifactorial issues. The goal is to understand the individual and adapt their lifestyle, diet, and exercise for the best outcome. However, don’t feel guilty or think obesity is the only problem. The aim is to reduce health risks for both the pregnancy and the future.
It depends on where you are treated. Fertility Clinics Abroad’s guide to BMI limits for IVF reports that NHS IVF in the UK is funded at a BMI of 19 to 30, private UK clinics usually treat to 35 and some to 40, US clinics set 35 to 45 with hospital units going higher, and no European country except Serbia limits IVF by BMI in law. Clinics abroad mostly work to 35 for own-egg IVF, and a number of clinics in Spain, Greece and North Cyprus assess patients above 35 case by case.
