Impact of BMI on fertility in an otherwise healthy population: a systematic review and meta-analysis

Florence Turner; Simon G Powell; Hannan Al-Lamee; Anjali Gadhvi; Ellen Palmer; Andrew Drakeley; Victoria S Sprung; Dharani Hapangama; Nicola Tempest

doi:10.1136/bmjopen-2023-082123

Lifestyle and Environment Nutrition and Metabolic Health

Impact of BMI on fertility in an otherwise healthy population: a systematic review and meta-analysis

Turner F, Powell SG, Al-Lamee H, Gadhvi A, Palmer E, Drakeley A, Sprung VS, Hapangama D, Tempest N

Published November 2024 BMJ open

DOI 10.1136/bmjopen-2023-082123 PMID 39486817 PMC PMC11529583

RRM Academy Synopsis

Higher BMI linked to fewer IVF pregnancies in otherwise healthy women

Women with a BMI of 25 or higher had lower odds of a clinical pregnancy in IVF cycles, a meta-analysis of eight cohort studies found. The studies enrolled 3770 patients without other diagnosed medical conditions. In these cycles, higher BMI also went with fewer mature eggs retrieved.

Key Findings

Eight IVF and ICSI studies were pooled, covering 4108 cycles from 3770 patients. Seven were retrospective cohort studies and one was a prospective cohort study.
In five studies, clinical pregnancy had lower odds at BMI 25 or higher (OR 0.76, 95% CI 0.62 to 0.93, p=0.007) and with obesity (OR 0.61, 95% CI 0.39 to 0.98, p=0.04).
In three studies, live birth favored healthy BMI over a BMI of 25 or higher (OR 1.32, 95% CI 1.05 to 1.65, p=0.02).
A BMI of 25 or higher went with fewer mature oocytes (SMD=-0.11, 95% CI -0.18 to -0.04, p=0.002) and longer ovarian stimulation (SMD=0.08, 95% CI 0.00 to 0.16, p=0.04).
Four studies reported miscarriage, with no statistical difference at a BMI of 25 or higher (OR 1.17, 95% CI 0.84 to 1.63, p=0.35).

Interpretation

The authors pooled observational cohorts, mostly retrospective. They excluded studies that enrolled women with conditions such as PCOS or thyroid disease. They report varying study quality and risk of bias. Live birth data came from only three studies. The results describe IVF and ICSI cycles, and the authors state they cannot be extrapolated to conception without IVF.

RRM Context

Eight of the nine eligible studies examined IVF or ICSI. The ninth followed couples conceiving without IVF. It reported an association between higher BMI and subfecundity, a time to pregnancy over 12 months (OR 1.32). Restorative reproductive medicine counts weight among the modifiable causes it evaluates.

Our editorial summary of this paper, not the article's abstract.

Abstract

Background

An increased body mass index (BMI) can lead to subfertility; however, current literature fails to exclude the effect of other confounding medical conditions, raising questions regarding the direct link between increased BMI and fertility outcomes.

Objectives

To conduct a systematic review and meta-analysis to elucidate the effects of increased BMI on fertility outcomes in females with no other comorbidities.

Search Strategy

A comprehensive search was conducted using EMBASE, MEDLINE and the Cochrane library from January 2000 until July 2023.

Data Collection and Analysis

Two authors independently conducted data extraction and assessed study quality. Odds ratio (OR) (dichotomous data), standardised mean difference (SMD) (continuous data) and 95% CIs were calculated.

Main Results

Nine eligible studies were identified: one natural conception and eight assisted reproductive technology (ART). Aggregated data revealed women with BMI ≥25 were less likely to attain clinical pregnancy (OR 0.76, 95% CIs 0.62 to 0.93, p=0.007), with BMI ≥30 associated with a further decreased likelihood of clinical pregnancy (OR 0.61, 95% CIs 0.39 to 0.98, p=0.04). Women with raised BMI required longer duration of stimulation (SMD=0.08, 95% CIs 0.00 to 0.16, p=0.04) and obtained reduced oocytes (SMD=-0.11, 95% CIs -0.18 to -0.04, p=0.002).

Conclusions

These data demonstrate an adverse impact of being overweight/obese on ART outcomes in women with no other diagnosed medical comorbidities and highlight the distinct lack of data concerning the effects of isolated obesity on natural conception. Infertility represents an enormous burden for couples and society; it is essential to identify and tackle modifiable risk factors to improve chances of conception.

Systematic Review Registration

CRD42022293631.

Topics

Lifestyle and Environment › Nutrition and Metabolic Health › Body Weight and Composition · Assisted Reproduction › Outcomes and Effectiveness › Outcomes by Diagnosis

Florence Turner, Simon G Powell, Hannan Al-Lamee, Anjali Gadhvi, Ellen Palmer, Andrew Drakeley, Victoria S Sprung, Dharani Hapangama, Nicola Tempest

F Turner, S Powell, H Al-Lamee, A Gadhvi, E Palmer, Andy Drakeley, Drew Drakeley, A Drakeley, V Sprung, D Hapangama, N Tempest

PMID 39486817 39486817 DOI 10.1136/bmjopen-2023-082123 10.1136/bmjopen-2023-082123 Turner et al. 2024, Turner 2024

Impact of BMI on fertility in an otherwise healthy population: a systematic review and meta-analysis

Higher BMI linked to fewer IVF pregnancies in otherwise healthy women

Key Findings

Interpretation

RRM Context

Abstract

Topics

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