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Effect of sex of fetus on asthma during pregnancy: blind prospective stud

BMJ 1998; 317 doi: (Published 26 September 1998) Cite this as: BMJ 1998;317:856
  1. N Beecroft, medical studenta,
  2. G M Cochrane, consultant physicianb,
  3. Heather J Milburn, consultant physicianb
  1. a United Medical and Dental Schools of Guy's and St Thomas's Hospital, Guy's Campus, London SE1 9RT
  2. b Department of Respiratory Medicine and Allergy, Guy's Hospital, London SE1 9RT
  1. Correspondence to: Dr H J Milburn, Chest Clinic, Guy's Hospital, London SE1 9RT

    The course of asthma during pregnancy is variable and may remain unchanged, worsen, or improve, returning to the pre-pregnancy state within three months after parturition.1 Some patients experience the same changes in each pregnancy, but nearly half do not, suggesting some intrinsic or extrinsic factor unique to each pregnancy such as the sex of the fetus.1 We observed that the condition of patients with moderate to severe asthma generally deteriorated when they were pregnant with girls but not boys, raising the intriguing possibility that the sex of the fetus might influence the course of asthma during pregnancy. We investigated this possibility in a blind prospective study.

    Subjects, methods, and results

    All women aged 25-34 who were receiving regular drug treatment for asthma and were in the second trimester of pregnancy (12-21 weeks' gestation) were approached directly to participate in the study. Twenty eight women were recruited from …

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