Weight & BMI While TTC
A normal BMI ranges from 19 – 24. A BMI from 25 – 29 is considered overweight, and a BMI >30 is considered obese. Many women who are in the underweight, overweight, and obese categories may have problems becoming pregnant. In fact, fertility is decreased in women who are very overweight and who are underweight as both conditions can interfere with normal ovulatory function.
Women with a BMI > 29 and underweight women with a BMI < 18 should schedule a thorough hormonal evaluation to check ovulation. It should be noted that women with a BMI >30 who have normal ovulation cycles still have lower pregnancy rates than women with a BMI within a lower range. In fertility treatments, overweight and obese women require higher doses of gonadotropins, have lower fertilization rates, and poorer embryo quality than those women with a healthier BMI.[i] Studies show that there is a higher rate of pregnancy loss in women with a BMI >30, and that the risk of pregnancy complications such as birth defects, gestational diabetes, and preeclampsia is also higher.
In men, a BMI >30 has been clearly linked to impaired sperm production including low sperm count and low sperm motility and is associated with changes in testosterone levels. Other health conditions such as diabetes, high blood pressure, elevated cholesterol, and being overweight can contribute to erectile dysfunction.
For these reasons, we do a comprehensive workup exploring all factors that could impact fertility, including BMI. At Carolina Conceptions, women with a BMI >40 are not candidates for fertility treatment and are encouraged to enroll in a weight loss program or consider the possibility of bariatric surgery as advised by their physician. To be eligible for IVF, the use of an egg donor (egg recipiency), or donor embryos (embryo recipiency), women need to have a BMI ≤ 37.5. We also encourage both partners to have a primary doctor and to be aware of family health history concerning diabetes, blood pressure, and cholesterol.
In both men and women, incorporating a healthy diet and regular exercise are first line interventions. Encouragingly, even a 5-10% decrease in weight (in an overweight individual) can lead to major health changes, including a boost in fertility. Gradual, sustained weight loss provides the most benefit. In one study researchers found that moderate physical activity in women improved time to pregnancy across the range of BMI.