From the Guidelines
For optimal fertility in Asian women, a BMI between 18.5-23 kg/m² is recommended, with the most recent and highest quality study suggesting that weight management through lifestyle interventions can improve fertility and live birth rates. This range is slightly lower than the normal range for the general population, reflecting ethnic differences in body composition. Asian women with BMIs below 18.5 may experience irregular menstrual cycles and ovulation issues due to insufficient body fat, which is essential for hormone production 1. Conversely, BMIs above 23 in Asian women can lead to insulin resistance, hormonal imbalances, and reduced egg quality, all of which can impair fertility.
Some key points to consider:
- A systematic review of 21 randomised controlled trials assessed non-pharmacological interventions for women diagnosed with infertility and with a BMI > 25 mg/m², and found that lifestyle interventions based on diet and physical activity leading to weight loss before conception can increase fertility and live birth rates 1.
- Weight management through balanced nutrition and regular physical activity is important for those outside this optimal range.
- A diet rich in whole grains, lean proteins, fruits, vegetables, and healthy fats can support both weight goals and reproductive health.
- For women with PCOS or other fertility issues, even modest weight changes of 5-10% toward this optimal range can significantly improve ovulation and pregnancy chances.
- Individual factors like muscle mass and fat distribution also matter, so consulting with healthcare providers for personalized guidance is recommended.
It's worth noting that the evidence on the influence of BMI on IUI success rates is contradictory, with some studies suggesting that a BMI of 25 kg/m² or more in the woman is associated with higher success rates, while others suggest that a BMI of <25 kg/m² is positively correlated with clinical pregnancy rates after IUI 1. However, the most recent and highest quality study suggests that weight management through lifestyle interventions can improve fertility and live birth rates, regardless of the specific BMI range 1.
From the Research
Optimal BMI for Fertility in Asian Women
- The optimal BMI for fertility in Asian women is not explicitly stated in the provided studies, but we can look at the relationship between BMI and fertility outcomes.
- A study published in 2014 2 analyzed data from 1529 live singleton deliveries in a multiethnic Singaporean population and found that the optimal gestational weight gain (GWG) varied by pre-pregnancy BMI category.
- The study found that the optimal GWG for normal weight women was 13.7 kg (range, 7.7 to 18.8), which corresponds to a pre-pregnancy BMI of 18.5-24.9 kg/m2.
- Another study published in 2024 3 found that women with a BMI ≥25 were less likely to attain clinical pregnancy, and women with a BMI ≥30 had a further decreased likelihood of clinical pregnancy.
- A 2016 study 4 found that reduced fecundability was observed among women with a BMI ≥30, and that moderate physical activity was associated with increased fecundability.
BMI Categories and Fertility Outcomes
- Underweight (BMI <18.5): optimal GWG was 19.5 kg (range, 12.9 to 23.9) 2
- Normal weight (BMI 18.5-24.9): optimal GWG was 13.7 kg (range, 7.7 to 18.8) 2
- Overweight (BMI 25-29.9): optimal GWG was 7.9 kg (range, 2.6 to 14.0) 2
- Obese (BMI ≥30): optimal GWG was 1.8 kg (range, -5.0 to 7.0) 2
- A BMI ≥25 was associated with decreased likelihood of clinical pregnancy 3
- A BMI ≥30 was associated with further decreased likelihood of clinical pregnancy 3