Asthma, Rhinitis, Other Respiratory Diseases
Mode of delivery and risk of allergic rhinitis and asthma,☆☆

https://doi.org/10.1067/mai.2003.34Get rights and content

Abstract

Background: It has been hypothesized that cesarean section might increase the risk of developing allergic disease by depriving the fetus and newborn of exposure to maternal microflora. Furthermore, it has been suggested that complicated modes of delivery might be associated with an increased risk of asthma. Objective: The purpose of this investigation was to study whether cesarean section and other complicated modes of delivery are associated with an increased risk of allergic rhinitis or asthma. Methods: Information on self-reported allergic rhinitis, asthma ever, current asthma, and occupation was obtained from 9722 singleton women born in Denmark during the period 1973-1977 who participated in a national cohort study during the period 1997-2001. For these women, information was available on mode of delivery (spontaneous delivery, cesarean section, vacuum extraction, or other complicated mode of delivery, such as rotation/traction or use of forceps), gestational age, birth weight, and length at birth from the Danish Medical Birth Register. Information on parity and maternal age was obtained from the Danish Civil Registration System. Results: The odds ratios (ORs) of allergic rhinitis were 1.16 (95% CI, 0.90-1.49) for cesarean section and 1.06 (95% CI, 0.85-1.32) for other complicated modes of delivery in comparison with spontaneous delivery. The corresponding ORs of asthma ever were 1.33 (95% CI, 1.02-1.74) and 1.18 (95% CI, 0.94-1.49) for cesarean section and other complicated modes of delivery, respectively, and the ORs of current asthma were 1.22 (95% CI, 0.87-1.73) and 1.26 (95% CI, 0.94-1.68), respectively, in comparison with spontaneous delivery. Conclusions: Our findings do not support the hypothesis that cesarean section or other complicated modes of delivery are associated with the development of allergic rhinitis. However, there might be a positive association with development of asthma—in particular, for cesarean section—that was not explained by gestational age, birth weight, ponderal index, smallness for gestational age, parity, maternal age, or occupation. (J Allergy Clin Immunol 2003;111:51-6.)

Section snippets

Methods

The study was nested in an ongoing national cohort study of pregnant women known as the Danish National Birth Cohort .17 Pregnant women were invited to participate in the study when they visited their general practitioners for the first time during pregnancy. An extensive telephone interview was conducted with each woman during pregnancy; it included a large variety of questions, among which were questions on asthma, allergy, and occupation. A total of 10,482 women from this cohort had been

Results

Of the 9722 women in the study, 1272 (14.0%) were cases of allergic rhinitis, 1038 (11.4%) were cases of asthma ever, and 644 (6.6%) were cases of current asthma. All of the women were between 20 and 28 years old, the median age being 25 years. In all, 87.9% of the women had been delivered spontaneously, 5.1% by cesarean section, 4.2% by vacuum extraction, and 2.7% by other complicated modes of delivery.

Table I shows the risk of allergic rhinitis according to the birth characteristics mode of

Discussion

In the present study, cesarean section was not associated with an increased risk of allergic rhinitis. This finding, together with the results of previous studies,4, 11, 12, 13 gives little support to the hypothesis that a modified colonization of the microbial flora in babies delivered by cesarean section should distort the development of the immune system so as to increase the risk of atopy and allergic disease into adulthood.

As regards asthma ever, we found a positive association with

Acknowledgements

We thank Dr Carsten Obel for fruitful discussions.

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    Supported by the Danish National Research Foundation (grant no. 11) and the Danish Medical Research Council (grant no. 9700560).

    ☆☆

    Reprint requests: Tine Westergaard, MD, PhD, Department of Epidemiology Research, Danish Epidemiology Science Centre, Statens Serum Institut, 5 Artillerivej, DK-2300 Copenhagen S, Denmark.

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