We all know that carrying too much weight can affect many areas of our health, but research has found that being overweight can also have a significant impact on your fertility. There are at least 3 ways that your weight affects your chances of becoming pregnant:
- It can disrupt your menstrual cycle
- It can change the quality of your eggs
- It can increase your risk of miscarriage
How much weight is too much?
íWhen it comes to fertility, your weight is measured according to your BMI, or body mass index. In general:
- A BMI below 18.5 is underweight
- A BMI between 18.5 and 24.9 is healthy
- A BMI between 25 and 29.9 is overweight
- A BMI over 30 is obese
That said, healthy weight is different for every woman. One woman could have a healthy BMI and experience weight-related fertility issues, while someone else who is overweight is able to get pregnant and give birth without any problems.
Excess weight can disrupt the menstrual cycle
The main way that extra weight affects fertility is by potentially disrupting your menstrual cycle.
Your menstrual cycle is regulated by a delicate balance of hormones produced by the pituitary gland and hypothalamus, and those glands stimulate your ovaries. The most important hormone is gonadotropin releasing hormone, or GnRH. It stimulates the production of follicle stimulating hormone (FSH), which starts egg development within the ovaries and raises your oestrogen levels, and leutinizing hormone (LH), which helps mature those eggs and release them on time.
Normally, the hypothalamus releases GnRH every one to two hours in a steady rhythm, but when you are overweight, the extra fatty tissue produces its own hormone, called leptin, which interrupts GnRH production and disrupts the entire menstrual cycle. The more extra fat you carry, especially when it’s around your abdomen, the more leptin your body produces.
Obesity also causes a drop in the production of sex hormone-binding globulin (SHBG) and growth hormone (GH), both of which are also involved in stimulating your ovaries to produce the right levels of androgen and oestrogen. According to one study, women who are obese are far less likely to conceive naturally within one year than women who are in the normal weight range.
Obesity can even lead to anovulation, which means that your ovaries simply stop producing eggs entirely because of the disruption to the hormonal balance. Women with a BMI over 27 are three times more likely to have stopped ovulating than women with a normal BMI.
Change in egg quality
Researchers are still investigating a link between obesity and a drop in egg quality, but it seems likely that even if you’re still ovulating, obesity decreases the quality of your eggs. As the egg divides repeatedly, it’s more likely to divide abnormally, generating eggs with the wrong number of chromosomes, and/or to fail to fertilize correctly.
A different study discovered that for every extra BMI point you have above 29, your chances of getting pregnant within 1 year drops by around 5%.
Miscarriage and birth
Scientists have also found that once you become pregnant, obesity can affect your chances of completing the pregnancy and giving birth to a healthy baby. According to the NHS, women who are obese have higher rates of miscarriage, higher risk of developing gestational diabetes, high blood pressure, and preeclampsia, and are more likely to experience complications when giving birth. The higher your BMI, the greater the risk.
A study found that even a little extra weight can have a surprising impact on miscarriages during IVF. Thirty-eight percent of women with a BMI of 25 or above miscarried during the first trimester, compared with 20% of women with a healthy BMI.
Male obesity and infertility
One more thing to bear in mind is that weight gain can cause infertility in men, too. Research indicates that men who are overweight, with a BMI above 25, have a 22% drop in sperm count and 24% drop in sperm concentrations. On top of that, testosterone levels fall when your BMI increases, which reduces the sex drive.
Weight isn’t the only thing that affects your fertility, and fibroids may complicate the process of conceiving, but if you’re struggling to conceive, and you have ruled out any other issues that could be preventing you from getting pregnant, you might want to consider losing weight.
We hope that your journey to pregnancy and parenthood goes smoothly and well.
