Maternal infections in pregnancy and the risk of sudden unexpected infant death in the offspring in the U.S., 2011–2015

BACKGROUND: Infection is thought to play a part in some infant deaths. Maternal infection in pregnancy has focused on chlamydia with some reports suggesting an association with sudden unexpected infant death (SUID). OBJECTIVES: We hypothesized that maternal infections in pregnancy are associated with subsequent SUID in their offspring. SETTING: All births in the United States, 2011–2015 DATA SOURCE: Centers for Disease Control and Prevention (CDC) Birth Cohort Linked Birth-Infant Death Data Files. STUDY DESIGN: Cohort study, although the data were analysed as a case control study. Cases were infants that died from SUID. Controls were randomly sampled infants that survived their first year of life; approximately 10 controls per SUID case. EXPOSURES: Chlamydia, gonorrhea and hepatitis C. RESULTS: There were 19,849,690 live births in the U.S. for the period 2011–2015. There were 37,143 infant deaths of which 17,398 were classified as SUID cases (a rate of 0.86/1000 live births). The proportion of the control mothers with chlamydia was 1.7%, gonorrhea 0.2% and hepatitis C was 0.3%. Chlamydia was present in 3.8% of mothers whose infants subsequently died of SUID compared with 1.7% of controls (unadjusted OR = 2.35, 95% CI = 2.15, 2.56; adjusted OR = 1.08, 95% CI = 0.98, 1.19). Gonorrhea was present in 0.7% of mothers of SUID cases compared with 0.2% of mothers of controls (OR = 3.09, (2.50, 3.79); aOR = 1.20(0.95, 1.49)) and hepatitis C was present in 1.3% of mothers of SUID cases compared with 0.3% of mothers of controls (OR = 4.69 (3.97, 5.52): aOR = 1.80 (1.50, 2.15)). CONCLUSIONS: The marked attenuation of SUID risk after adjustment for a wide variety of socioeconomic and demographic factors suggests the small increase in the risk of SUID of the offspring of mothers with infection with hepatitis C in pregnancy is due to residual confounding.