“Women with poorly managed asthma have a higher chance of giving birth early or having a small baby,” reported BBC News.
This news is based on a systematic review that combined data from 26 cohort studies looking at whether having asthma increases a pregnant woman’s risk of having complications at around the time of giving birth. The researchers specifically looked at pre-eclampsia during pregnancy, baby’s birthweight and size for gestational age, as well as timing of delivery, i.e. whether the baby was born full term or premature.
The review indicated that maternal asthma was associated with an increased risk for all of these outcomes. However, when the reviewers separately analysed five studies which clearly described that the asthma was being appropriately managed with medications, there was no longer an increased risk of prematurity in these studies. This suggests that any risks of asthma during pregnancy may be mitigated by active asthma management.
Prior research is reported to have given conflicting results over whether asthma has any effect on pregnancy outcomes. Most importantly, these findings demonstrate the importance of appropriate control of asthma symptoms. The study’s authors call for further research to determine optimal asthma management techniques for pregnant women.
Pregnant women with asthma should continue to take their asthma medications as prescribed. They should consult their doctor if they find that their symptoms are worsening during pregnancy.
The study was carried out by researchers from the University of Newcastle and Hunter Medical Research Institute and the John Hunter Hospital in Australia, the Scripps Clinic, Kaiser Permanente Medical Center and University of California-San Diego in the US. The study was funded by the Kaiser Permanente Southern California Regional Research Committee and the Australian National Health and Medical Research Council.
The research was published in the peer-reviewed British Journal of Obstetrics and Gynaecology.
The findings were reported accurately by BBC News.
The aim of this study was to establish whether maternal asthma is associated with an increased risk of adverse perinatal outcomes (during the weeks preceding and immediately following birth) and to determine the size of these effects.
The research involved a systematic review and meta-analysis of cohort studies, published between 1975 and 2009, which had examined this association, including maternal pre-eclampsia (high blood pressure and protein in the urine during pregnancy, which can be associated with other complications), birthweight and size for gestational age, premature labour and delivery.
A systematic review is a way of collecting as much of the research evidence on a particular question as possible. High-quality systematic reviews use rigorous methods to find, collate and assess the quality of the studies that are included.
A meta-analysis pools the findings of the included studies and analyses the data as a large set. Looking at the data in this way increases the ‘power’ (ability) of the analysis to detect an effect. The power of the analysis increases with the number of participants that are included. For instance, this systematic review included 40 publications involving 1,637,180 participants, far more than any single study could examine on its own.
The researchers conducted a literature search, and included studies for analysis if:
Researchers extracted data on various perinatal outcomes, and compared the risk of seeing these outcomes in women with and without asthma.
The researchers assessed the quality (risk of bias) in each of the selected studies, and analysed the data by pooling the results in several different ways.
First, researchers assessed the risk of developing each outcome in women with asthma compared to women without asthma. They then conducted a subgroup analysis, where they looked at five studies which specifically described that women with asthma were being actively managed with appropriate medications. They also looked at 10 studies where no active management was described. They then examined the risks in women who were receiving active asthma management, and looked at the risks in women who were not described as receiving active management.
The analysis included 26 studies involving 1,637,180 individuals. These studies had been reported in 33 published research papers.
The researchers found that, compared to women without asthma, women with asthma had:
When the researchers analysed the studies separately according to degree of active asthma management, they found that in the studies where women with asthma were appropriately managed there was:
The 10 studies reporting no active management had shown a significantly increased risk of these outcomes.
The researchers conclude that pregnant women with asthma are at increased risk for a variety of perinatal conditions, including having pre-eclampsia, pre-term delivery, having a baby of low birthweight and small size for gestational age. They also conclude that active management of asthma mitigates these risks, especially that of pre-term delivery.
Prior research is reported to have found conflicting results on whether asthma has any effect on pregnancy outcomes. This study aimed to review the available literature to see whether maternal asthma is associated with an increased risk of complications around the time of late pregnancy and birth.
Performing a systematic review and meta-analysis can increase the statistical power of research on a topic, helping to detect differences in outcomes. This review was large, and its authors report high statistical power for the analyses. This may be the case, but there are still some important points to note when considering the results:
As the authors of this review have noted, further research into optimal asthma management techniques during pregnancy is warranted. Pregnant women with asthma should continue to take their asthma medications as prescribed, and should consult their doctor if they find that their symptoms are worsening during pregnancy.