How high (and low) BMI can affect fertility

A large population study using two analytical approaches finds a consistent association between BMI measurements and subfertility; a predicted BMI of 23 in women and 25 kg/m2 in men was linked to the lowest subfertility risk.

A large population study has found a ‘causal effect’ of obesity on subfertility in both men and women. This cohort analysis from the Norwegian Mother, Father and Child Cohort Study, included a population of 28,341 women and 26,252 men recruited between 1999 and 2008 and found direct associations between high and low BMI and risk of subfertility.

The study reports coincide with publication of a revised ASRM committee opinion on obesity and reproduction which cautions that, ‘although obesity increases the risk of infertility, most men and women with obesity are fertile’.(4) Obesity in women, the report reaffirms, is associated with ovulatory dysfunction, reduced ovarian responsiveness to agents that induce ovulation, altered oocyte as well as endometrial function, and lower birth rates after IVF. In men, reproductive function ‘may be impaired’. The opinion concludes, however, that obesity ‘should not be the sole criteria for denying a patient or couple access to infertility treatment’, but that ‘prepregnancy counseling for couples with obesity should address the reproductive and maternal–fetal consequences of obesity’.

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