Role of Maternal ABO Blood Type on Neonatal Outcomes
Authors: McGinnis Danielle , Shine Kailey , Iben Danielle , Holthaus Emily , Zoma Marim , Baran Kim , Muraskas Jonathan , DeChristopher Phillip , Glynn Loretto 
Published: July 2024

Purpose: This retrospective chart review investigates the association between maternal AB blood type and neonatal outcomes including birthweight, NICU transfer rate, Apgar scores, cord blood pH levels, clinical chorioamnionitis, and stillbirth compared to other maternal blood types (A, B, and O). Methods: Delivery records were examined from the electronic medical record (EMR) for deliveries occurring between 1/1/2020 and 12/31/2022. Some variables were autofilled from nurse-entered data into the EMR during the delivery encounter (blood type, maternal age, Body Mass Index (BMI), gestational age at delivery, mode of delivery, presence of Category 2 tracing, infant birth weight, NICU transfer, Apgar scores, and cord gas values). Missing data were obtained through chart review. Other variables obtained through chart review included maternal gravida and para numbers, clinical chorioamnionitis diagnosis, fetal growth restriction, stillbirth, indications for delivery and cesarean section, hypertensive disorders of pregnancy, and medical history including chronic hypertension and gestational and pregestational diabetes. Comparisons between maternal blood type AB vs. all other blood types (group containing blood types A, B, and O) were completed using Student’s t-tests, Mann Whitney U tests, Pearson’s chi-square tests, or Fisher’s Exact tests as statistically appropriate. Comparisons between the 4 individual blood types (AB, A, B, O) were completed using ANOVA, Pearson’s chi-square tests, or Kruskal-Wallace tests as statistically appropriate. Post-hoc multivariate linear regression was used to examine associations of interest identified on bivariate analysis. Results: A total of 3263 deliveries were reviewed between 1/1/2020 and 12/31/2022. Of these, 113 patients had blood type AB (3.46%) and 3150 had other blood types (1015 type A (31.07%), 463 type B (14.18%), 1672 type O (51.28%)). Patients with blood type AB had statistically higher age than other blood types (31.0 ± 5.2 vs. 29.9 ± 6.1, p = 0.046) and lower BMI (31.2 [interquartile range 7] vs. 33 [IQR 9.5], p = 0.009). There were no differences in nulliparity, gestational age at delivery, chronic hypertension, gestational diabetes, cholestasis of pregnancy, clinical chorioamnionitis, fetal growth restriction, stillbirth, category 2 tracing, or mode of delivery. No statistically significant differences were observed in birthweight between infants born to mothers with blood type AB (mean: 3227 grams, SD: 694 grams; p = 0.158) compared to those born to mothers with other blood types (mean: 3195 grams, SD: 734 grams; p = 0.158). The rates of NICU transfer were similar between the two groups, with 12% of infants born to blood type AB mothers requiring NICU admission compared to 17% of infants born to mothers with other blood types (p = 0.162). Apgar scores at 1, 5, and 10 minutes did not significantly differ between the two groups (p > 0.05). Additionally, there were no significant differences in cord arterial pH (AB: 7.26 ± 0.06 vs. others: 7.25 ± 0.07; p = 0.649) and cord venous pH (AB: 7.33 ± 0.06 vs. others: 7.32 ± 0.06; p = 0.860). Furthermore, when comparing the individual maternal blood types with 4-way comparisons, similar findings of no significance were observed for Apgar scores, cord arterial and venous pH levels, clinical chorioamnionitis diagnosis, fetal growth restriction diagnosis, stillbirth, category 2 notes, and delivery or C-section indication for category 2 tracing (p > 0.05). The Kruskal Wallace test comparing birthweight between the 4 blood types showed p = 0.055. A multivariate linear regression for birthweight did not show a significant association for blood type (p = 0.201) when controlling for maternal age, BMI, hypertensive disorder of pregnancy, chronic hypertension, diabetes, and gestational age. Conclusion: The impact of maternal ABO blood type on neonatal outcomes remains a topic of interest in obstetric and perinatal medicine. We have previously demonstrated newborn AB blood type is associated with significant morbidity and mortality with necrotizing enterocolitis (NEC), as well as a higher incidence of respiratory distress syndrome, retinopathy of prematurity, and sepsis (McMahon et al., 2019). Previous studies have independently provided evidence of adverse pregnancy outcomes for type AB mothers (Fan et al., 2023) and type AB neonates. However, there are conflicting findings regarding the association between maternal ABO blood type and neonatal outcomes. Our findings suggest that neonatal outcomes, including birthweight, NICU transfer rate, Apgar scores, cord blood pH levels, clinical chorioamnionitis, and stillbirth do not significantly differ between infants born to mothers with blood type AB and those born to mothers with other blood types. These results indicate that other factors may play a more substantial role in determining neonatal health and outcomes. Further research with additional perinatal measures is warranted to explore the potential influence of blood type and other factors on neonatal health.