The study included more than 100,000 pregnancies and found that children of women who had asthma attacks during pregnancy were also at increased risk for asthma and other respiratory problems in the first 5 years of life.
“Asthma is the most common chronic disease in pregnant women, affecting 8%-13% of pregnant women worldwide,” author Kawsari Abdullah, PhD, a research fellow at the Children’s Hospital of Eastern Ontario Research Institute in Ottawa, Canada, said in a news release. Abdullah was at the Hospital for Sick Children in Toronto when the study was being conducted.
Almost 40% of women with asthma stop taking their asthma controller medications during pregnancy out of concern that these medications may harm the fetus, according to senior author Teresa To, PhD, also from The Hospital for Sick Children.
The researchers analyzed administrative data from the Ontario Asthma Surveillance System and five other healthcare administrative databases. The study included data from 103,424 singleton pregnancies in 58,524 women with asthma between April 2003 and March 2012. Asthma exacerbations occurred in 2663 women with asthma and a total of 4455 pregnancies.
The investigators defined asthma exacerbations as five or more physician visits, one emergency department visit, or one hospital admission for asthma during pregnancy. They adjusted results for mother’s age, number of prior births, maternal smoking during pregnancy, rural residence, socioeconomic status, the baby’s sex, and comorbidities.
Increased Risks for Mother and Infant
Compared with women with asthma who had no prenatal exacerbations, those who had exacerbations had 30% higher odds of preeclampsia (odds ratio [OR], 1.30; P < .001; 3.84% vs 5.32%, respectively; p < 0.001), and 17% higher odds of pregnancy-induced hypertension (OR, 1.17; P = .022; 5.37% vs 7%, respectively; P < .001).
Compared with children born to mothers without prenatal asthma attacks, those born to mothers with prenatal asthma exacerbations had 14% higher odds of low birth weight (OR, 1.14; P = .049; 5.28% vs 6.76%, respectively; P < .001), 14% higher odds of preterm birth (OR, 1.14; P = .036; 6.66% vs 8.15%, respectively; P < .001), and 21% higher odds of birth defects (OR 1.21; P = .007; 4.97% vs 6.2%, respectively; P < .001).
In the first 5 years of life, children born to mothers with prenatal asthma exacerbations also had 23% higher risk of developing asthma (risk ratio [RR], 1.23; p < .001; 31.39% vs 37.77%, respectively; P < .001) and 12% higher risk for pneumonia (RR, 1.12; P < .006, 21.69% vs 24.38%, respectively; P < .001).
Past studies have linked prenatal asthma attacks to serious complications in the mother, including pregnancy-induced hypertension and preeclampsia. If untreated, the latter can lead to life-threatening eclampsia.
Asthma attacks during pregnancy can also contribute to preterm delivery, low birth weight in newborns, birth defects, and newborn death. Longer-term effects on offspring may include increased risk for asthma, allergic rhinitis, and other lung or allergic conditions.
Most of this evidence comes from small studies, however.
“This is the biggest study looking at the risks associated with severe asthma symptoms in pregnancy, and it’s also the first to show the longer-term impacts on children up to the age of 5 years. Our results reinforce the findings of smaller studies that uncontrolled asthma can be bad for mothers and their babies,” To explained.
The study had several potential limitations. Because they lacked information on the severity of asthma exacerbations and asthma medications, the researchers could not evaluate their impact on mother and child. Although asthma medications such as oral corticosteroids may contribute to adverse outcomes, the authors note that having a severe asthma attack may pose a higher risk.
“This study does not explain why asthma attacks contribute to all these health issues, but the likely mechanism is reduced oxygen supply for the mother and subsequently to the baby in the womb,” Jørgen Vestbo, DrMedSci, FRCP FERS, FMedSci, said in a press release. Vestbo, who was not involved in the study, is chair of the European Respiratory Society’s Advocacy Council and a professor at the University of Manchester, United Kingdom.
“This large and important study suggests that asthma that is not well controlled may have serious effects on pregnant women and their children. This highlights the importance of carefully maintaining asthma control and managing asthma symptoms during pregnancy. Pregnant women who have asthma need regular antenatal care to discuss their symptoms and ensure their medication is effective,” Vestbo stressed.
The study was supported by the Institute for Clinical Evaluative Sciences , with an annual grant from the Ontario Ministry of Health and Long-Term Care.