Infertility, pregnancy loss and assisted reproduction in women with asthma: a population-based cohort study
Authors: Jöud Anna , Nilsson-Condori Emma , Schmidt Lone , Ziebe Søren , Vassard Ditte , Mattsson Kristina 
Published: October 2022

Abstract

STUDY QUESTION
Is the chance of childbirth, and risk of infertility, pregnancy loss and need for assisted reproduction different for women with asthma compared to women without asthma?

SUMMARY ANSWER
Women with asthma had comparable chances of giving birth compared to the reference population, however, their risk of both infertility and pregnancy loss, as well their need for medically assisted reproduction, was higher.

WHAT IS KNOWN ALREADY
Reproductive dysfunction has been reported among women with asthma, including longer time to pregnancy, increased risk of pregnancy loss and a higher need of medically assisted reproduction, but their risk of clinical infertility is unknown.

STUDY DESIGN, SIZE, DURATION
This longitudinal register-based cohort study included all women with a healthcare visit for delivery, infertility, pregnancy loss or induced abortion in the southernmost county in Sweden, over the last 20 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS
Using the Skåne Healthcare Register, we identified all women aged 15–45 between 1998 and 2019, who received a diagnosis of asthma before their first reproductive outcome (n = 6445). Chance of childbirth and risk of infertility, pregnancy loss and assisted reproduction were compared to a healthcare seeking population of women without any asthma (n = 200 248), using modified Poisson regressions.

MAIN RESULTS AND THE ROLE OF CHANCE
The chance of childbirth was not different between women with asthma versus those without, adjusted risk ratio (aRR) = 1.02, 95% CI: 1.01–1.03. The risk of seeking care for infertility was increased, aRR = 1.29, 95% CI: 1.21–1.39, and women with asthma more often needed assisted reproduction aRR = 1.34 95% CI: 1.18–1.52. The risk of suffering a pregnancy loss was higher, aRR = 1.21, 95% CI: 1.15–1.28, and induced abortions were more common, aRR = 1.15, 95% CI: 1.11–1.20, among women with asthma.

LIMITATIONS, REASONS FOR CAUTION
The study was an observational study based on healthcare visits and lacked detailed anthropometric data, thus residual confounding cannot be excluded. Only women with a healthcare visit for a reproductive outcome were included, which cannot be translated into pregnancy intention. A misclassification, presumed to be non-differential, may arise from an incorrect or missing diagnosis of asthma or female infertility, biasing the results towards the null.

WIDER IMPLICATIONS OF THE FINDINGS
This study points towards reproductive dysfunction associated with asthma, specifically in regards to the ability to maintain a pregnancy and the risk of needing medically assisted reproduction following clinical infertility, but reassuringly the chance of subsequently giving birth was not lower for these women.

STUDY FUNDING/COMPETING INTEREST(S)
This article is part of the ReproUnion collaborative study, co-financed by EU Interreg ÖKS, Capital Region of Denmark, Region Skåne and Ferring Pharmaceuticals. The authors have no competing interests to disclose.

TRIAL REGISTRATION NUMBER
N/A.