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Overweight: how it affects IVF treatment and pregnancy
Article written by Dr Katharina Spies, Medical Director at Vida Fertility
The link between overweight and fertility is one of the most frequently asked questions in the field of assisted reproduction.
Many patients come to us concerned because they have been trying to get pregnant for some time and wonder whether their weight might be a factor. Others have already begun fertility assessments and want to know whether they can start IVF, whether they need to lose weight first, or whether overweight might reduce their chances of getting pregnant.
We spoke to Dr Katharina Spies about whether overweight affects female and male fertility.
At Vida Fertility, we don’t just look at a BMI figure. We assess age, ovarian reserve, ovulation, hormonal status, metabolic health, semen analysis (if there is a male partner) and the safety of the treatment.
- 1. Does overweight affect fertility?
- 2. Why can overweight cause infertility?
- 3. How does overweight affect IVF?
- 4. Do I need to lose weight before starting fertility treatment?
- 5. What are the chances of getting pregnant if you are overweight?
- 6. Pregnancy risks associated with overweight
- 7. Frequently asked questions about overweight and fertility
- 7.1. How does being overweight affect fertility?
- 7.2. Can I undergo IVF if I am obese?
- 7.3. Does overweight affect male fertility?
- 7.4. What is the recommended BMI for IVF?
- 7.5. Does overweight affect hormonal medication in assisted reproduction?
- 7.6. Can my fertility treatment be cancelled because of my weight?
- 8. Are there any fertility clinics specialising in treating overweight patients?
- 9. Our fertility treatments
- 10. The best fertility clinics in Spain
Does overweight affect fertility?
Yes. overweight can affect fertility because fatty tissue plays a role in hormonal and metabolic processes. When a person is overweight, this can lead to insulin abnormalities, low-grade inflammation, changes in hormone levels and problems with ovulation.
In some women, this results in irregular cycles, a lack of ovulation or difficulty in becoming pregnant. In others, ovulation continues, but there may be other associated factors, such as insulin resistance, polycystic ovary syndrome, SOMP, thyroid disorders or increased obstetric risk.
However, whilst overweight can impair fertility, it should not be considered an absolute cause without a comprehensive fertility assessment.
Why can overweight cause infertility?
Overweight can be a cause of infertility in both men and women.
Overweight and female fertility
In women, it can disrupt ovulation, affect egg quality, alter the hormonal environment of the endometrium and increase the risk of complications during pregnancy. It may also mean that some treatments require more careful planning.
How does overweight affect ovulation?
Obesity can disrupt ovulation because adipose tissue plays a role in hormonal metabolism and can influence oestrogen production, insulin resistance and the balance between the hormones that regulate the menstrual cycle.
Does overweight reduce egg quality?
Obesity can influence the metabolic environment in which oocytes mature.
This does not mean that all women with overweight have poor-quality eggs or that they cannot achieve pregnancy. Oocyte quality also depends on age, ovarian reserve, genetics, lifestyle and medical history
In some patients, excess adipose tissue is associated with low-grade inflammation, oxidative stress, hormonal imbalances and insulin resistance – factors that can affect oocyte maturation and, consequently, egg quality.
Does being overweight affect embryo implantation?
In some women with overweight, there may be less favourable endometrial receptivity, abnormalities in blood supply, increased systemic inflammation or hormonal changes that hinder synchronisation between the embryo and the endometrium. This can affect the chances of implantation, even when good-quality embryos are transferred.
Nevertheless, embryo implantation is a complex process and does not depend solely on weight. Other factors also play a role, including embryo quality, oocyte quality, the condition of the uterus, the presence of polyps or fibroids, the endometrial microbiota in selected cases, and other immunological or thrombophilic factors where indicated.
Does overweight increase the risk of miscarriage?
Obesity is associated with an increased risk of pregnancy loss, particularly where there is insulin resistance, hormonal imbalances, low-grade chronic inflammation or associated metabolic conditions, such as type 2 diabetes or hypertension.
However, it is important to note that miscarriage is a multifactorial process.
- Maternal age
- The genetic quality of the embryo
- Uterine abnormalities
- Endocrine factors
- Immunological factors
- Thrombophilic factors
- Male factors may also play a role
Therefore, we should not attribute a pregnancy loss solely to the patient’s weight.
Overweight and male fertility
In men, overweight and male fertility are also linked. Being overweight may be associated with poorer semen quality, hormonal abnormalities, lower testosterone levels, erectile dysfunction or increased sperm DNA fragmentation.
Does weight affect semen quality?
This can result in lower sperm concentration, reduced motility, abnormalities in morphology or reduced fertilising capacity.
Furthermore, overweight may be associated with insulin resistance, systemic inflammation, oxidative stress and erectile dysfunction – factors which can also affect the likelihood of achieving pregnancy.
Infertility may be female, male , mixed, or linked to other factors. This is why it is important to carry out a preliminary assessment using the necessary fertility tests for each individual case.
A comprehensive diagnosis enables the most appropriate treatment to be chosen: ranging from lifestyle changes and metabolic optimisation to techniques such as IVF or ICSI when indicated.
How does overweight affect IVF?
Obesity can influence various stages of in vitro fertilisation treatment. During ovarian stimulation, some patients may require adjustments to their medication or may have a less predictable ovarian response. At the time of egg retrieval, the medical team must assess the safety of the anaesthesia and the technical difficulty of the procedure.
It can also affect endometrial preparation, implantation and the risk of complications once pregnancy has been achieved. This does not mean that IVF is not possible, but rather that it must be carried out using a well-planned strategy.
When discussing IVF in patients with a high body mass index, the key is to assess whether the treatment can be carried out safely, what risks are involved and what aspects we can optimise before starting.
Do I need to lose weight before starting fertility treatment?
It depends on each individual case. For some patients, losing weight before starting treatment can improve ovulation, reduce metabolic risks and better prepare the body for pregnancy. For others, particularly those of advanced reproductive age or with low ovarian reserve, delaying treatment for many months may reduce their chances of success.
That is why, at Vida Fertility, we do not provide a standardised answer. There are patients for whom we recommend a nutrition programme before starting fertility treatment, and others for whom we can proceed with the assessment, evaluate ovarian reserve and design a parallel plan: improving metabolic health without wasting reproductive time.
What are the chances of getting pregnant if you are overweight?
There is no single figure, as the likelihood of pregnancy depends on many factors: age, ovulation, ovarian reserve, sperm quality, fallopian tubes, medical history, lifestyle and type of treatment.
Being overweight can reduce the chances in some cases, particularly if there is anovulation or metabolic disorders. However, there are overweight women who conceive naturally and women with a normal BMI who require assisted reproduction.
Pregnancy risks associated with overweight
Obesity can also increase certain risks during pregnancy, such as gestational diabetes, high blood pressure, pre-eclampsia, caesarean section or anaesthetic complications.
This approach is particularly important in assisted reproduction. Before IVF, it is advisable to assess general health, metabolism, blood pressure and other factors that may influence the safety of the treatment and the pregnancy.
Frequently asked questions about overweight and fertility
How does being overweight affect fertility?
It can affect ovulation, hormonal balance, egg quality, the endometrium and the risk of complications during pregnancy. In men, it can affect semen quality.
Can I undergo IVF if I am obese?
In many cases, yes. For some patients, we recommend a nutrition programme before starting fertility treatment, whilst for others we can proceed with the assessment, evaluate ovarian reserve and design a parallel plan: improving metabolic health without wasting reproductive time.
However, it is always necessary to assess the safety of the treatment, the anaesthesia, the ovarian response and the risks associated with pregnancy.
Does overweight affect male fertility?
Yes. It can be associated with hormonal imbalances, poorer semen quality and greater difficulty in achieving pregnancy.
What is the recommended BMI for IVF?
An abnormal BMI, whether too low or too high, can interfere with the hormonal, ovulatory and metabolic processes that are key to conception. There is no single recommended BMI for IVF that applies to all patients.
For this reason, before starting IVF, we assess not only BMI, but also age, ovarian reserve, ovulation, blood pressure, glucose metabolism, medical history and the safety of undergoing egg retrieval under sedation.
As fertility specialists, we agree that the ideal range for BMI and fertility should be between 18.5 and 24.9. This does not mean that it is impossible to conceive outside this range, but it does mean that the chances are reduced.
Does overweight affect hormonal medication in assisted reproduction?
Yes, overweight can influence the response to hormonal medication in assisted reproduction. In some cases, women with ob overweight esity may require adjustments to their gonadotropin doses during ovarian stimulation, as the ovaries’ response may be less predictable.
This does not mean that the medication does not work, but rather that the treatment must be carefully monitored. During IVF, we monitor follicular growth using ultrasound scans and hormone tests to tailor the medication to each patient’s response. The aim is to achieve stimulation that is both effective and safe.
Furthermore, overweight may co-occur with insulin resistance, polycystic ovary syndrome, thyroid disorders or other metabolic factors that also influence the hormonal response. For this reason, before starting treatment, it is advisable to carry out a comprehensive assessment and, where possible, address any factors that may interfere with ovarian stimulation or endometrial preparation.
Can my fertility treatment be cancelled because of my weight?
Fertility treatment may be postponed or reconsidered for medical safety reasons, but weight should not be used as the sole automatic criterion for cancelling or refusing treatment. The decision must be based on a comprehensive clinical assessment.
At Vida Fertility, we approach these cases on a case-by-case basis. Our aim is not to exclude a patient because of her weight, but to assess how we can help her in the safest possible way, minimising risks and avoiding unnecessary delays on her journey to pregnancy.
Are there any fertility clinics specialising in treating overweight patients?
Yes, Vida Fertility has established itself as a group of fertility clinics specialising in complex cases of infertility.
The important thing is to go to a clinic that assesses each case individually, without placing blame, and which can coordinate assisted reproduction, nutrition, exercise, endocrinology and medical follow-up if necessary.
Obesity and fertility: when to seek advice
If you are obese or overweight and have been trying to conceive for some time, or if you are considering starting fertility treatment, it is best not to wait. An initial assessment can help you understand your ovulation cycle, the state of your ovarian reserve, whether there is a male factor, and what options are available to you.
At Vida Fertility, we address overweight and fertility with a medical, realistic and respectful approach. It’s not about judging your body, but about understanding what your reproductive health needs to move forward safely.
Book an appointment with the medical team at Vida Fertility. Dr Zermiani and our team can assess your case and help you design the best plan to achieve pregnancy.
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