Obesity and asthma during pregnancy: a systematic review and meta-analysis

Abstract

Objective: To assess the effect of obesity on the prevalence of asthma, obstetric outcomes and delivery outcomes in pregnant women with asthma.

Methods: A comprehensive systematic review and meta-analysis were conducted up to 31 March 2024, using four public search engines. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, both quantitative and qualitative data were collected and analysed.

Results: We included 11 studies from 2006 to 2022 involving 77 611 386 pregnant patients (3.1% had asthma). Obesity increased the odds of asthma (n=2; OR 2.42, 95% CI 1.14-5.15) and increased that of uncontrolled asthma (n=6; OR 1.29, 95% CI 1.11-1.50) in pregnant women. In an adjusted pooled analysis, pregnant women with asthma were more likely to develop hypertensive disorders of pregnancy (HDP) (n=3; adjusted OR (aOR) 1.21, 95% CI 1.10-1.34), gestational diabetes mellitus (GDM) (n=3; aOR 1.14, 95% CI 1.04-1.26), fetal growth restriction (FGR) (n=2; aOR 1.18, 95% CI 1.15-1.21), preterm birth (PTB) (n=2; aOR 1.26, 95% CI 1.25-1.27), caesarean delivery (CD) (n=3; aOR 1.22, 95% CI 1.11-1.33) and severe maternal morbidity (n=1; aOR 1.50, 95% CI 1.45-1.55). Three comparator studies that examined the effect of obesity on obstetric outcomes cited obesity as a risk factor for HDP (n=1; aOR 1.7, 95% CI 1.3-2.3), GDM (n=1; aOR 4.2, 95% CI 2.8-6.3) and CD (n=1; aOR 1.6, 95% CI 1.3-2.0) in pregnant women with asthma.

Conclusions: Pregnancy with asthma may increase the risk of HDP, GDM, FGR, PTB and CD, and obesity has the potential to further increase the risk of HDP, GDM and CD in pregnant women with asthma.

Overview of the study findings. CD: caesarean delivery; FGR: fetal growth restriction; GDM: gestational diabetes mellitus; HDP: hypertensive disorders of pregnancy; PTB: preterm birth; SMM: severe maternal morbidity; Unc: uncontrolled.

FIGURE 1

Scheme of the systematic literature search and study selection. ^#: During the title screening, 620 studies were excluded because they were nonasthma studies, nonpregnancy studies, ineligible study types or non-English articles. ^¶: During the abstract screening, 158 studies were excluded because they were nonasthma studies, nonpregnancy studies, noncomparative studies, studies on asthma in childhood, ineligible study types or had no relevant outcomes.

FIGURE 2

Meta-analysis of the association between obesity and asthma during pregnancy. The prevalence of a) asthma in pregnant women with and without obesity and b) the prevalence rates of uncontrolled asthma in pregnant women with and without obesity. Heterogeneity among the studies in each analysis was determined and a random-effects analysis was performed because of considerable heterogeneity (a) I²=100%; b) I²=68%). Some of the values listed above might be slightly different from the original values because of the calculations in RevMan^TM version 5.4.1. IV: inverse variance; M-H: Mantel–Haenszel test; Unc: uncontrolled asthma.

FIGURE 3

Meta-analysis of the effect of asthma on obstetric outcomes. Pooled odds ratios for a) unadjusted and b) adjusted analyses for hypertensive disorders of pregnancy (HDP), c) unadjusted and d) adjusted analyses for gestational diabetes mellitus (GDM), e) unadjusted and f) adjusted analyses for fetal growth restriction (FGR) are shown. Heterogeneity among the studies in each analysis was determined. Random-effects analysis was performed due to the considerable heterogeneity (a) I²=97%; b) I²=75%; c) I²=94%; d) I²=62%; e) I²=96%). In the analysis with no heterogeneity (f) I²=0%), a fixed analysis was applied. Some values listed above might be slightly different from the original values because of the calculation in Revman^TM version 5.4.1. IV: inverse variance; M-H: Mantel–Haenszel test.

FIGURE 4

Meta-analysis of the effect of asthma on delivery outcomes. Pooled odds ratios for a) unadjusted and b) adjusted analyses for preterm birth (PTB), c) unadjusted and d) adjusted analyses for caesarean delivery (CD), and e) unadjusted and f) adjusted analyses for postpartum haemorrhage (PPH) between pregnant women with and without asthma. Heterogeneity among the studies in each analysis was determined. Random-effects analysis was applied due to the considerable heterogeneity among the studies (d) I²=92%; e) I²=98%; f) I²=96%). In an examination of no heterogeneity (a, b and c) I²= 0%), a fixed pooled analysis was performed. Some values listed above might be slightly different from the original values because of the calculation in Revman^TM version 5.4.1. IV: inverse variance; M-H: Mantel–Haenszel test.