Use of asthma drugs is less among women pregnant with boys rather than girls

Editor—Beecroft et al reported an intriguing association between the sex of the fetus and symptoms of asthma during pregnancy.¹ They speculated that women pregnant with boys have improved asthma symptoms during pregnancy, possibly because of androgen production by male fetuses. We recently reported a population based study from Nova Scotia, Canada, of perinatal outcomes in women with asthma during pregnancy, but we did not consider fetal sex.²

Although we do not have specific data on asthma severity or symptoms, pregnant asthmatic women were divided into three treatment groups: no use of drugs during pregnancy, β agonists alone, and steroids with or without other asthma drugs. The table shows that 14% of women pregnant with a boy required steroids during pregnancy compared with 20% of women pregnant with a girl. Conversely, more women pregnant with a girl used β agonists alone than did women pregnant with a boy.

If asthmatic patients requiring steroids are assumed to have more severe symptoms than those not taking steroids or those taking β agonists alone, our data support the association noted by Beecroft et al. Unfortunately, we cannot confirm this assumption and conclude that this interesting association is worthy of further study.

Table.

Sex of fetus and use of asthma drugs among asthmatic women during pregnancy. Values are numbers of women (percentages of male or female fetuses)

Sex of fetus	No drug treatment (n=375)	β agonist alone (n=303)	Steroids (n=139)
Male (n=415)	192 (46)	164 (40)	59 (14)
Female (n=402)	183 (46)	139 (35)	80 (20)