Background: Rh(D) alloimmunization prophylaxis should be administered to unsensitized Rh(D)-negative pregnant women. A routine antenatal dose and a postpartum dose for women that delivered an Rh(D)-positive neonate are recommended. Due to a very low prevalence of Rh(D)-negative blood type in Thai population, awareness of this specific management may be lacking.

Objective: To determine the proportion of unsensitized Rh(D)-negative pregnant women that delivered at Siriraj Hospital who received a complete course of anti-D immunoglobulin and to determine the factors associated with the failure to achieve a complete administration as well as pregnancy and neonatal outcomes.

Materials and Methods: Medical records of 133 unsensitized Rh(D)-negative pregnant women were reviewed to determine the proportion of cases receiving a complete anti-D prophylaxis. Possible reasons for missing anti-D administration were postulated. Comparison between cases receiving and not receiving antenatal anti-D prophylaxis was performed in terms of associated factors. Pregnancy and neonatal outcomes were compared between women who received complete prophylaxis and those who did not.

Results: A complete anti-D prophylaxis was obtained in 71.4% of the women with antenatal dose given to 78.2%. Late antenatal care (OR 2.6, 95% CI 1.4 to 4.9) and late or no antenatal care at Siriraj Hospital (OR 7.1, 95% CI 2.8 to 17.9) were associated with missing antenatal anti-D administration. Desire for tubal sterilization and positive maternal Rh(D)-antibody in the third trimester appeared to be the causes of postpartum dose omission. Pregnancy and neonatal outcomes were comparable between women receiving and not receiving a complete anti-D prophylaxis.

Conclusion: The proportion of unsensitized Rh(D)-negative pregnant women delivering at Siriraj Hospital who received a complete anti-D prophylaxis was 71.4%. Late antenatal care, late or no antenatal care at Siriraj Hospital, desire for tubal sterilization, and positive maternal Rh(D)-antibody in the third trimester were associated with the incomplete Rh(D) alloimmunization prophylaxis.

Keywords: Rh(D)-negative, Alloimmunization, Anti-D immunoglobulin, Anti-D prophylaxis, Rh immunoglobulin

DOI: doi.org/10.35755/jmedassocthai.2021.04.12071

Received 21 September 2020 | Revised 23 December 2020 | Accepted 25 December 2020