Prevalence of infant outcomes at birth after exposure to interferon beta prior to or during pregnancy : a register-based cohort study in Finland and Sweden among women with MS

• Introduction: Women with multiple sclerosis (MS) are often diagnosed and treated at childbearing age. Systematic reviews and registry studies suggest that MS and interferon-beta (IFNβ) expo-sure might affect birth weight and head circumference.Objectives: To determine the prevalence of categorical measures of birth weight for gestational age (small for gestational age (SGA), large for gestational age (LGA)), low birth weight, and low head circumference in IFNβ exposed and unexposed pregnant women with MS from health registers in Finland and Sweden.Methods: In this cohort study, health register data from Finland (1996-2014) and Sweden (2005-2014) were used to study women with MS 1) dispensed only IFNβ within 6 months prior to date of last menstrual period or during pregnancy (IFNβ-exposed) and 2) without any dispensed MS disease modifying drugs (MSDMDs) (unexposed). The prevalence, with 95% confidence interval (CI), of the following birth outcomes was described for the IFNβ-exposed and the unexposed: SGA, LGA, low birth weight for live births, and low head circumference for infants with full term live birth (at least 37 gestational weeks). For SGA, LGA, and head circumference, national gestational age and sex-specific national references were used. No adjustments for potential confounding factors were performed.Results: Among 666 IFNβ-exposed and 1330 unexposed live births, the prevalence of the infant outcomes were similar between the IFNβ-exposed vs the unexposed. Comparing the exposed vs unexposed, SGA was 2.1% (95%CI 1.2-3.5) vs 2.0% (95%CI 1.3-2.9), and LGA 0.8% (95%CI 0.2-1.7) vs 0.8% (95%CI 0.4-1.5).The prevalence of low birth weight was 3.9% (95%CI 2.6-5.7) among IFNβ-exposed and 4.8% (95%CI 3.7-6.1) among the unexposed live births. Among 619 IFNβ-exposed and 1219 unexposed full term live births, the prevalence of low head circumfer-ence was 1.9% (95%CI 1.0-3.4) among the IFNβ-exposed vs 1.1% (95%CI 0.6-1.8) among the unexposed births.Conclusions: The data from Finnish and Swedish health registers showed no evidence that IFNβ exposure before and during pregnancy affected infant birth weight and head circumference.

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MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Neurologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Neurology (hsv//eng)

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