Do BMI and age affect IVF and fertility? Clínica Tambre answer your questions

We recently ran a poll asking what you’d like to know more about from our partner leading fertility specialists. Of all the suggested topics: you wanted more information on age and weight when trying to conceive.

With this in mind, we’ve turned to trusted fertility clinic Clínica Tambre in Madrid, Spain, who delve into optimal weight for fertility and IVF success, as well as what age (and ovarian reserve) means for fertility.

So, we want to know: alongside age, how much does weight really affect fertility?

BMI and fertility

Body weight can play an important role in fertility and conception.

Adipose (fatty) tissue produces oestrogen, so the more adipose tissue there is, the higher the levels of this hormone can become in the body. In response, the brain decreases the production of two hormones, LH and FSH, which stimulate the ovaries. As a result, the ovaries can enter a state of rest and ovulation may stop. Without ovulation, fertilisation and pregnancy are not possible.

A higher body mass index (BMI) is also associated with a greater chance of miscarriage in the first three months of pregnancy (the risk is even higher when the BMI is over 25).

Weight can affect male fertility, too. Adipose tissue produces inflammation, which can affect both the quantity and mobility of sperm.

Is it safe to lose weight while trying to conceive?

Losing weight while trying to conceive is recommended and safe, as long as it is done under the supervision of a (fertility) nutritionist and with a well-balanced diet, so that no nutrients are missing.

If you’re otherwise healthy, how important is your BMI when TTC?

A BMI above 25 is related to a decrease in fertility and an increase in the first-trimester miscarriage rate.

For IVF, why is a BMI of 30 (marking obesity) a cut-off for the NHS? Is this based on scientific evidence?

It is a cut-off that the NHS has determined, but this is related to studies in the scientific literature that correlate BMI with the success of assisted reproduction techniques.

What are the consequences of a higher BMI in terms of stopping the embryos from implanting or anything else?

A high BMI is related to hyperestrogenism (increased levels of estrogens in the blood), which alters the ovarian response to ovarian stimulation medication and can also alter the quality of the endometrium (womb lining).

Does weight prevent people from being able to have IVF or IUI?

Excess weight and obesity can lower the success of IVF and IUI.

Exercise during IVF

What kind of exercise is advisable during IVF Stimulation and the two-week wait?

Gentle exercise is good, such as walking, yoga, swimming (pre transfer), etc.

High-intensity exercise and vigorous physical activity should be avoided during ovarian stimulation, as there may be a risk of follicle rupture, ovarian torsion and/or abdominal pain.

Is it possible that too much physical exercise can have a negative effect on fertility?

For women, intense physical exercise can lower reproductive capacity because it can cause disorders like amenorrhea (absence of menstruation), which indicates the absence of ovulation and with that the impossibility of becoming pregnant.

For men who do very intense physical exercise and consume steroids or anabolic agents, this can sometimes reduce the testosterone hormone levels, as well as diminishing the size of the testicles and the number of sperm, therefore causing male infertility.

Ovulation and anovulation

In your twenties, how long is it likely to take to ovulate, having just come off the pill?

Most women without health problems in their twenties ovulate correctly in the first cycle after stopping the pill. Studies show that in the following three cycles, 98% of women have ovulated.

Ovarian reserve and age

Is it possible to improve your ovarian reserve without hormone injections?

The ovarian reserve unfortunately cannot be improved by drugs or lifestyle changes because it is something that is genetically determined.

When you have a low AMH level, how can you improve egg quality and health?

In cases of low ovarian reserve, the only thing we know is that ovarian quality is closely related to age.

Clinical studies have shown that adopting a healthy lifestyle and adding specific fertility supplements, such as antioxidants and vitamins increases the percentage of eggs that develop into good quality embryos.

Why do miscarriages occur more often?

Miscarriage has increased mainly because of the rising average age at which women begin to seek pregnancy, which is above 30 years in almost all European countries. The increase in maternal age is the main cause of genetic abnormalities in embryos, which in turn is the main cause of miscarriage. Before the age of 30, the risk of suffering a miscarriage is less than 10%, whereas after the age of 42, the risk is almost 75%.

In recent years, there has also been an increase in maternal pathologies related to miscarriage, such as diabetes, thrombophilia, antiphospholipid syndrome and hypertension. Excess weight or malnutrition also play a role. From the male point of view, there are studies that show that exposure to toxins from work or excessive consumption of coffee, tea and chocolate can cause alterations in the sperm that can increase the risk of miscarriage.

What advice do you have for someone trying to conceive at 40 or older?

From 40 onwards, the quality and quantity of the eggs is worse and this leads to a decrease in fertility. The chances of achieving a natural pregnancy are much lower so, if pregnancy is not achieved, it is advisable not to wait more than 6 months before consulting an assisted reproduction clinic.

In addition, after 40 the risk of complications is greater, so it is very important to control all modifiable risk factors such as diet and lifestyle to try to reduce all other risks. Weight control is very important because it is related to an increase in hypertension and gestational diabetes during pregnancy, which are two more frequent pathologies in women over 40.

A big thanks to Clinica Tambre for their insightful answers to these topical questions on the effects of age and weight on IVF / fertility.

If you’d like to find out more from their fantastic team of experts, you can message them here.