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Weight and Fertility: How Your Weight Can Affect Your Ability to Get Pregnant

fertility weight

Ask any ObGyn or reproductive endocrinologist: weight definitely matters when it comes to fertility. Women who are overweight - or underweight - tend to have a more difficult time conceiving. The same goes for men, but more about that later.

First things first, though: How do you determine if you're over or underweight? One commonly used indicator is to look at your Body Mass Index, or BMI, which provides a helpful indication of where you fall on the spectrum. Enter your vital information in the calculator below to determine your BMI:

Body Mass Index

The recommended 'healthy' BMI range for trying-to-conceive women is between 18.5 and 24.9. A BMI over 25 is considered 'overweight' and anything beyond

30 is considered 'obese'. On the other side of the equation, anything under 18.5 is considered 'underweight'.

Now, armed with that information: What are the problems associated with being overweight (a BMI of 25 or more) when trying to conceive? One common issue relates to a potential imbalance of the hormone estrogen. Fat cells actually produce estrogen, and consequently, women with more fat cells tend to have higher levels of estrogen. This can negatively impact your fertility, essentially acting as a birth control of sorts by preventing adequate ovulation from occurring. Women experiencing inadequate ovulation are prone to "luteal phase defect". The luteal phase is the phase from ovulation to menstruation. Typically, the ideal length is between 12 and 14 days; however, women suffering from luteal phase defect have a luteal phase that is too short to sustain pregnancy (less than 10 days).

Polycystic Ovary Syndrome (PCOS) is a common cause of infertility, and is closely linked to a tendency in women to gain weight and/or experience difficulty in losing weight. A diagnosis of PCOS may help you to determine the best path of treatment and assist with any attendant weight issues. Other factors commonly associated with PCOS include irregular cycles (making it hard to determine your fertile days), ovarian cysts, excess body hair (hirsutism), and even heavy, painful periods. Some women with PCOS may also experience elevated LH levels, linked to a higher likelihood of miscarriage.

But how about being underweight, with a BMI of less than 18.5? How does that impact fertility? Being underweight may cause you to experience anovulation (a lack of ovulation), irregular ovulation, and may lead to irregular menstrual cycles. This is due to the fact that the amount of a woman's body fat correlates to the amount of hormones her body produces. Simply put, being underweight can result in insufficient production of key hormones, leading to ovulatory issues which make it difficult to achieve pregnancy. Specifically, insufficient production of GnRH (gonadotrophin releasing hormone) can lead to inadequate development of a uterine lining capable of supporting pregnancy. GnRH also triggers the release of LH (luteinizing hormone) and FSH (follicle-stimulating hormone), necessary in the development of eggs and for ovulation to occur.

This Just In: Your Man is NOT Off the Hook When it Comes to Weight

Men are not to be forgotten in this equation. Male infertility can also be affected by weight. Low sperm count and motility issues occur with greater prevalence in overweight men due to the excess layers of fat surrounding the testicles. This phenomenon leads to an increase in temperature which can kill, or negatively affect the development of, sperm. Being underweight can also affect sperm count, motility, and morphology. For men who want to determine if they are considered in the 'normal' range for weight - the same range applies. It is best to be between 18.5 and 24.9 BMI when trying-to-conceive.

Bottom line: It's helpful for women and men who are over or underweight to know exactly how that may be impacting their ability to get pregnant. The good news is that, for many people, adjusting your body weight to adhere to the 'healthy' BMI range often leads the body to restore normal hormonal balance. As always, a consultation with your doctor is recommended to determine the best plan for weight loss (or gain).