Differences in maternal-newborn ABO blood groups and risk of serious infant infection.

BACKGROUND: During pregnancy, various maternal IgG antibodies are transferred to the developing fetus, some of which may protect the newborn against infection. If a mother and her fetus have different ABO blood groups, then transferred maternal antibodies may plausibly protect the infant against infection. AIM: To determine if maternal-newborn ABO blood group incongruence vs. congruence is associated with a lower risk of serious infection in the infant. DESIGN: Retrospective population-based cohort. METHODS: We used linked patient-level datasets for all singleton hospital livebirths from 2008-2022 in Ontario, Canada, with known maternal and newborn ABO blood groups. We used a dichotomous exposure state, either ABO blood group congruent (N = 114,507) or incongruent (N = 43,074). The main outcome of interest was the risk of serious infant infection within 27 days, and from 28-365 days, after birth. Cox proportional hazard models generated hazard ratios and 95% confidence intervals, and were adjusted for maternal age, world region of origin, residential income quintile, and gestational age at birth. RESULTS: Relative to maternal-newborn congruency, incongruent ABO blood group was associated with aHR of 0.88 (95% CI 0.80 to 0.97) for serious neonatal infection within 27 days of birth, and 0.93 (95% CI 0.90 to 0.96) for serious infection between 28-365 days after birth. CONCLUSIONS: Maternal-newborn ABO incongruence may be associated with a lower relative risk of a serious infant infection within 27 days, and from 28 to 365 days, after birth.

ABO and Rh blood groups and risk of infection: systematic review and meta-analysis.

BACKGROUND: Persons with non-O and Rh-positive blood types are purported to be more susceptible to infection, including SARS-CoV-2, but there remains uncertainty about the degree to which this is so for both non-viral and viral infections. METHODS: We systematically reviewed Embase and PubMed from January 1st 1960 to May 31st 2022. English-language publications were selected that separately investigated the relation between ABO and/or Rh blood group and risk of SARS-CoV-2 and non-SARS-CoV-2 infection. Pooled odds ratios (ORp) and 95% confidence intervals (CI) were then generated for each. RESULTS: Non-O blood groups had a higher ORp for SARS-CoV-2 than O blood groups, both within 22 case-control studies (2.13, 95% CI 1.49- 3.04) and 15 cohort studies (1.89, 95% CI 1.56- 2.29). For non-SARS-CoV-2 viral infections, the respective ORp were 1.98 (95% CI 1.49-2.65; 4 case-control studies) and 1.87 (95% CI 1.53-2.29; 12 cohort studies). For non-viral infections, the ORp were 1.56 (95% CI 0.98-2.46; 13 case-control studies) and 2.11 (95% CI 1.67-6.67; 4 cohort studies). Rh-positive status had a higher ORp for SARS-CoV-2 infection within 6 case-control studies (13.83, 95% CI 6.18-30.96) and 6 cohort studies (19.04, 95% CI 11.63-31.17), compared to Rh-negative persons. For Rh status, non-SARS-CoV-2 infections, the ORp were 23.45 (95% CI 16.28-33.76) among 7 case-control studies, and 9.25 (95% CI 2.72-31.48) within 4 cohort studies. High measures of heterogeneity were notably observed for all analyses. CONCLUSIONS: Non-O and Rh-positive blood status are each associated with a higher risk of SARS-CoV-2 infection, in addition to other viral and non-viral infections.

Indicators of Cardiometabolic Function in Pregnancy and Long-Term Risk of COVID-19: Population-Based Cohort Study.

BACKGROUND: Pregnancy increases a woman's susceptibility to severe COVID-19, especially those with metabolic dysfunction. It is unknown if markers of metabolic dysfunction commonly assessed around pregnancy are associated with COVID-19 illness after pregnancy. AIM: The aim of this study is to evaluate the indicators of metabolic dysfunction collected in pregnancy and the future risk of severe COVID-19 after pregnancy. METHODS: This population-based cohort study was completed in all of Ontario, comprising 417,713 women aged 15-49 years with a hospital birth between April 2007 and March 2018. The main exposure was each 1-kg/m2 higher body mass index (BMI), 1-mmol/L higher glucose concentration at the 50-g glucose challenge test, and one-week earlier gestational week at delivery. The main outcome was severe COVID-19 illness or death, from the start of the pandemic period on March 1, 2020, till December 31, 2021. RESULTS: The adjusted hazard ratio (aHR) of COVID-19 illness increased per 1-kg/m2 higher BMI (1.05, 95% CI 1.04-1.06), per 1-mmol/L higher serum glucose concentration (1.16, 95% CI 1.10-1.22), and for each one-week earlier gestational week at delivery (1.12, 95% CI 1.03-1.23). Relative to women with no dichotomized risk factors, the aHR for severe COVID-19 was 1.60 (95% CI 1.28-2.01) with one factor, 3.34 (95% CI 2.51-4.44) with two factors, and 4.52 (95% CI 2.11-9.67) with three factors. CONCLUSIONS: The number, and degree, of standard metabolic indicators measured around pregnancy predict the future risk of severe COVID-19 remotely after that pregnancy.