OC Use Before Pregnancy Does Not Increase Offspring Asthma Risk

Barbara Boughton

March 31, 2011

March 31, 2011 (San Francisco, California) — New research disproves the theory that there is an association between birth control pills and risk for asthma in offspring — a hypothesis suggested by several studies since the late 1990s, according to researchers here at the American Academy of Allergy, Asthma and Immunology (AAAAI) 2011 Annual Meeting.

One of the largest studies that has ever been done on the question, using the Norwegian Mother and Child Cohort, has revealed no increased risk for respiratory outcomes such as infections, wheezing, and asthma in offspring after use of combination birth control pills, according to lead author Dana Hancock, PhD, a genetic epidemiologist with the nonprofit Research Triangle Institute International in Research Triangle Park, North Carolina.

The research was published online February 7 in Pediatric Allergy and Immunology.

The database used for the study, the Norwegian Mother and Child Cohort, is a compilation of data regarding 100,000 pregnancies with follow-up information on children up to age 7 or 8 years. "It's a massive database, and provided us with a wealth of information about the use of birth control pills and its relationship to respiratory outcomes in children," Dr. Hancock said.

The researchers did find a slightly increased risk for wheezing in children aged 6 to 8 months (odds ratio, 1.19) who were the offspring of mothers who had taken progestin-only birth control pills in the year before pregnancy. Yet this result may have been a result of residual confounding, as use of progestin-only pills in the Norwegian cohort was much less common compared with use of combination pills, Dr. Hancock said.

"Overall, birth control pills don't appear to increase risk for respiratory tract infections or symptoms of asthma. This research should provide reassurance to mothers that their prior use of oral contraceptives won't have an impact on respiratory symptoms in their children," Dr. Hancock said.

Although previous studies had suggested an association between use of hormonal medications and fetal respiratory development, the Norwegian study should make the choice of whether or not to use birth control pills an easier one, particularly for women who may be concerned about asthmatic symptoms in their children because of family or personal history, Dr. Hancock said.

In the study, Dr. Hancock and colleagues looked at associations between the type of oral contraceptive used by mothers before pregnancy and lower respiratory tract infections in 60,225 children followed up to 6 months of age. The researchers also analyzed the relationship between use of both types of birth control pills and lower respiratory tract infections and wheezing in 42,250 children followed up to age 18 months. In addition, the researchers assessed associations between use of oral contraceptives and development of asthma in 24,472 children followed up to age 36 months.

Even though the increased association between wheezing and progestin-only pills was small, it may suggest that future studies should look at these oral contraceptives and combination pills separately, Dr. Hancock noted.

"There has been concern that the hormonal changes of pregnancy may be associated with asthma, so taking hormonal supplements of any type might increase your risk for having asthmatic children," commented Mitchell Grayson, MD, associate professor of pediatrics, medicine, microbiology and molecular genetics at the Medical College of Wisconsin in Milwaukee.

"This study does provide some warm fuzzy feelings that prior use of oral contraceptives before pregnancy is probably not a risk factor for asthma. And it suggests that use of birth control pills before pregnancy is safe," Dr. Grayson added. "But I don't think it's an issue that will change clinical practice; it's not a question that pops up every day in the allergist's office," he said.

Dr. Hancock and Dr. Grayson have disclosed no relevant financial relationships.

American Academy of Allergy, Asthma and Immunology (AAAAI) 2011 Annual Meeting: Abstract 662. Presented March 21, 2011.

Pediatr Allergy Immunol. Published online February 7, 2011.

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