Use of Antiasthmatic Drugs during Pregnancy after the First Trimester and Maternal and Neonatal Outcomes

Background. Women with asthma using antiasthmatics during the later part of the pregnancy have an increased risk for obstetric complications and their infants of neonatal complications. Material and Methods. The study is based on a linkage between the Swedish Medical Birth Register and a register of prescribed drugs in Sweden for the years 2009–2011, identifying women who had filled prescriptions for antiasthmatics after the first trimester. Their characteristics, their obstetric history, and the neonatal conditions of their infants were compared with all other women who gave birth. Adjusted Mantel-Haenszel odds ratios were determined. Results. We found an increased risk for a number of maternal conditions but no risk increase for gestational diabetes (after adjustment for body mass index) or for premature rupture of membranes. There was an increase in preterm births for some drugs used at severe asthma and of low birth weight and small for gestational age for most drug combinations. An increased risk was seen for neonatal hypoglycemia, respiratory problems, and low Apgar score. Conclusions. There are many hazards associated with maternal asthma and use of antiasthmatic drugs. Most evidence suggests a disease effect. A careful control of the asthma during pregnancy is important. 1. Introduction Many articles and reviews are available on the subject of asthma and the use of antiasthmatic drugs during pregnancy. One review [1] summarized the early literature. More recent reviews have been published [2–4]. In most studies which were large enough, an association with various maternal obstetric morbidities was demonstrated. On the other hand, the effect on preterm birth, low birth weight, and intrauterine growth retardation is more uncertain and results vary. A recent paper [5] studied the issue of congenital malformation risk after early pregnancy exposure to antiasthmatic drugs and a weak general increase was found which could not be attributed to any specific antiasthmatic drug and most likely was due to the effect of the underlying disease. In the present study, the effect of use of antiasthmatics later in pregnancy is studied. 2. Material and Methods The study was based on the Swedish Medical Birth Register [6] which contains medical information on practically all deliveries in Sweden since 1973, including information on delivery and neonatal diagnoses. Information on the use of antiasthmatic drugs was obtained from the Swedish Prescribed Drugs Register [7]. Women giving birth during 2009–2011 were searched in this register and the filling of