# The Allelic and Phenotypic Frequencies of the ABO and Rh Blood Types in Pregnant Women in Addis Ababa, Ethiopia

## TL;DR

This study analyzed the ABO and Rh blood type frequencies in pregnant women in Addis Ababa, Ethiopia, finding Type O as the most common and a 5% risk of erythroblastosis fetalis.

## Contribution

The study provides updated allelic and phenotypic frequencies of ABO and Rh blood groups in pregnant women in Ethiopia.

## Key findings

- Type O blood was the most common (38.9%) among pregnant women.
- 94.2% of women were Rh-positive, with a 5% likelihood of erythroblastosis fetalis.
- ABO and Rh blood groups followed Hardy–Weinberg equilibrium proportions.

## Abstract

Background: ABO–rhesus (Rh) blood testing screens blood types according to the antigenic properties of red blood cells.

Objective: This study reports the allelic and phenotypic frequency distribution of the ABO and Rh blood groups in pregnant women who attended antenatal care (ANC) at Zewditu Memorial Hospital in Addis Ababa, Ethiopia, and the likelihood for the occurrence of erythroblastosis fetalis (E. fetalis).

Methods: A retrospective study was conducted on pregnant women who attended ANC from 2015 to 2019 and typed for ABO and Rh blood groups. The Hardy–Weinberg equilibrium was used to determine the allelic frequency of ABO and Rh blood types. The likelihood of the occurrence of E. fetalis was computed.

Results: Among the 2453 women who had been admitted to ANC, 2407 (98.1%) pregnant women who had been typed for the ABO and Rh blood groups were included in this retrospective study. We found that Type O blood was the most common one (38.9%), while Types A (31.3%), B (23.8%), and AB (6.0%) blood were scored with modest to lower proportions. Among blood group–typed women, 94.2% were Rh-positive. The allelic frequency of O was 0.62, whereas A (0.22) and B (0.16) had modest proportions. The allelic frequency of D was 0.76 and d was 0.24. The likelihood of the occurrence of E. fetalis was 5%. Our findings show that both the ABO (χ‐squared = 6.1439, df = 3, p value = 0.1048) and the Rh (χ‐squared = 0.000103, df = 1, p value = 0.9919) blood groups were segregated at the Hardy–Weinberg proportions. Studies need to investigate the evolutionary forces that have made the ABO and Rh blood types segregate at the Hardy–Weinberg proportion.