Fluconazole in first trimester not associated with increase in most birth defects

Image: PD 

1. Oral fluconazole use in the first trimester was not associated with an increase overall birth defects. 

2. However, oral fluconazole was associated with an increase in tetralogy of Fallot. 

Evidence Rating Level: 2 (Good) 

Study Rundown:  Pregnant women are at increased risk of vaginal candidiasis, for which a single dose of oral fluconazole is common therapy.  However, fluconazole has been previously associated with various birth defects including Tetralogy of Fallot.  The authors performed a registry-based cohort study to examine the relationship of oral fluconazole in the first trimester with birth defects.  They found that there was no association between fluconazole and an increase in birth defects overall.  This study would appear to dispel most fears of fluconazole’s association with birth defects previously specified in case reports and prior cohort studies.  However, fluconazole was associated with a slight but signifcant increase of Tetraology of Fallot (0.10% vs 0.03%), While the study’s method for determining exposure to fluconazole of prescription history eliminates recall bias, it does not account for potential noncompliance and therefore information bias.  Additionally, the reassurance from this study can only be applied to first trimester use of fluconazole.  Given the large number of patients included in the study, the data overall are reassuring that fluconazole use in the first trimester does not appear to be associated with an increase in overall birth defects, although further study should probe its relationship to Tetralogy of Fallot.

Click to read the study, published today in NEJM

Background Reading: Maternal use of fluconazole and risk of congenital complications

In-Depth [registry based cohort study]: The authors selected a nationwide cohort of live births in Denmark between 1996 and 2011 using the Medical Birth Registry. Using the National Prescription Registry, they identified those exposed to fluconazole as those women who filled a prescription for oral fluconazole during their first trimester.  Those women who did not fill a prescription for oral fluconzole were counted as unexposed.  They then identified birth defects through the National Patient Register.  They then calculated odds ratios based on prevalence of birth defects in the exposed and unexposed groups.  The study included a total of 976,300 infants of which 8064 were exposed to oral azole agents according to the study’s parameters.  They found that there was no significant difference in the prevalence of birth defects in the exposed and unexposed populations (2.86% vs 2.60%, with OR 1.06, 95%CI 0.92-1.21).  When comparing prevalence of specific birth defects between groups, all had similar levels with the exception of tetrology of Fallot which showed an increased prevalence in the exposed group (0.10% in exposed vs 0.03% in unexposed, adjusted prevalence odds ratio, 3.16; 95% CI, 1.49 to 6.71). 

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