Researchers published the study covered in this summary on researchsquare.com as a preprint that has not yet been peer reviewed.
Key Takeaways
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In a large cohort of women with a body mass index (BMI) below 30 kg/m2 receiving up to four intrauterine insemination (IUI) infertility treatments in China, those with underweight were significantly less likely to become pregnant or have a live birth, whereas women with overweight were significantly more likely to have these positive outcomes, compared with women of normal weight (BMI 18.5-24.9 kg/m2).
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In a regression analysis that adjusted for potential confounders, women with underweight had a 23% lower rate of a live birth per cycle whereas women with overweight had a 24% higher rate of this outcome compared with women of normal weight.
Why This Matters
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Although IUI is often suggested as a first treatment for infertility due to its simplicity and lower cost than in vitro fertilization (IVF), it has not been as well studied as IVF and study results have shown conflicting outcomes.
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Prior research has primarily focused on the poorer outcomes associated with obesity, and some studies excluded women with underweight or pooled their data with that of women with normal BMI.
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The results suggest that clinicians and patients should be aware that underweight is associated with a lower live-birth rate when using the IUI form of assisted reproduction.
Study Design
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This was a retrospective review of 6407 women who received 13,745 cycles (4769 natural cycles and 8976 stimulated cycles) of IUI as part of infertility treatment at Chenggong Hospital, which is affiliated with Xiamen University, in China, from July 2015 to December 2020.
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The women among the couples in the study had at least one documented patent fallopian tube, and the men had prewash total motile sperm counts above 1 million in pretreatment evaluations.
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The review excluded women with bilateral tubal pathology, thyroid disease, or other endocrine disorders, a BMI ≥ 30 kg/m2, or if they received attempted IUI more than four times.
Key Results
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Among the total of 13,745 fertilization cycles included in the analysis, 16% were in women with underweight (BMI < 18.5 kg/m2), 71% were in women with normal weight, and 13% were in women with overweight (BMI 25.0-29.9 kg/m2).
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After up to four IUI procedures and adjusting for possible confounders, compared with women of normal weight, women with underweight were a significant 15% less likely to become pregnant and a significant 20% less likely to have a live birth.
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After adjustment, women with overweight were a significant 19% more likely to become pregnant and a significant 19% more likely to have a live birth compared with women with normal weight.
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When calculated as a live birth rate per cycle and after adjustment, compared with women with normal weight, women with underweight had a significant 23% lower rate while women with overweight had a significant 24% higher rate.
Limitations
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The study was retrospective.
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The study may include a selection bias because women with high BMIs may have been advised to lose weight before IUI treatment.
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The patients with a low BMI may have had unknown chronic conditions that contributed to unidentified confounding.
Disclosures
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The study did not receive commercial funding.
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The authors reported no financial disclosures related to this research.
This is a summary of a preprint research study, “Low BMI is associated with poor IUI outcomes: a retrospective study in 13,745 cycles” written by researchers at Chenggong Hospital affiliated with Xiamen University, China. Preprints from Research Square are provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on researchsquare.com.
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