Chest
Volume 98, Issue 2, August 1990, Pages 389-392
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Intrauterine Growth Is Related to Gestational Pulmonary Function in Pregnant Asthmatic Women

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Asthmatic mothers have been reported to deliver infants of lower mean birth weight than nonasthmatic mothers. This study examined the relationship between intrauterine growth and serial gestational spirometry in 352 pregnant asthmatic women who were prospectively treated and observed during pregnancy. A small (r = 0.11) but significant (p<0.04) direct correlation was demonstrated between infant birth weight and individual mean percent predicted FEV1 during pregnancy. In addition, lower maternal mean FEV1 during pregnancy was associated with increased incidences of birth weight in the lower quartile of the infant population (p = 0.002) and ponderal indices <2.2 (suggestive of asymmetric intrauterine growth retardation) (p<0.05), but not with increased incidences of preterm (<38 weeks) or low birth weight (<2,500 g) infants. Although lower mean birth weight occurred in infants of smoking compared with nonsmoking asthmatic mothers (p<0.02), the relationships of lower FEV1 to birth weight in the lower quartile of the population (odds ratio 3.0, p = 0.002) and ponderal indices <2.2 (odds ratio 2.8, p<0.05) were shown by multivariate analysis to be above and beyond the influence of smoking and also independent of the effects of age, parity, acute asthmatic episodes, and asthma medications. These data support the hypothesis that lower maternal gestational FEV1 during pregnancy is related to intrauterine growth retardation and suggest that the goals of gestational asthma therapy should include optimization of pulmonary function in addition to achievement of symptomatic control.

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Subjects and Clinical Assessment during Pregnancy

Subjects were participants in the Kaiser-Permanente Prospective Study of Asthma during Pregnancy, the design of which has been previously described.4 This report describes 360 pregnancies in women with documented asthma4 who delivered singleton births ≥20 weeks’ gestation between June 1978 and December 1984. Asthma was prospectively managed during pregnancy by a study allergist (M.S.) in an attempt to prevent acute episodes of asthma and asthma symptoms that interfered with sleep or normal

RESULTS

Eight subjects in whom less than three FEV1 determinations were obtained during pregnancy were excluded from FEV1 analyses. The number of FEV1 determinations obtained during pregnancy in the remaining 352 subjects ranged from three to 25 (median, 7.0). No significant relationship was observed between the number of FEV1 determinations obtained in each patient and the individual mean percent predicted FEV1.

A small (r = 0.11) but significant (p<0.04) correlation was demonstrated between individual

DISCUSSION

Bahna and Bjerkedal1 reported that the mean birth weight of 378 infants of asthmatic mothers (3,400 g) was nearly 100 g less than the mean birth weight of 112,328 infants of nonasthmatic mothers (p<0.001). The data in the present report confirm the hypothesis that chronic maternal gestational pulmonary function (mean percent predicted FEV1) is related to infant birth weight in pregnant asthmatic women. The association in this study of lower maternal FEV1 with both lower birth weight and an

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Presented in part at the Annual Meeting, American Academy of Allergy and Clinical Immunology, Anaheim, California, March 15, 1988.

Publication No. 3 from the Kaiser-Permanente Prospective Study of Asthma During Pregnancy, supported in part by grant AI 20426 from the Allergy and Asthma Branch of the National Institute of Allergy and Infectious Diseases; by grants from William H. Rorer-Dooner Laboratories and Kaiser Foundation Hospitals; with supplemental support from Key Pharmaceuticals and Boehringer-Ingelheim, Ltd.

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