Maternal-fetal isoimmunisation of an Rh-negative mother pregnant with an Rh-positive fetus can occur in the third trimester of pregnancy, but occurs especially at the time of delivery.
Other times of risk for maternal isoimmunisation to occur include:
- After an ectopic pregnancy.
- After a miscarriage or voluntary termination of pregnancy.
- When an invasive procedure is performed in pregnancy.
- If an external cephalic version is required.
- When vaginal bleeding occurs in pregnancy.
- If a trauma or blow to the womb occurs while pregnant.
Therefore, at 28 weeks gestation, after delivery and after all these situations, Rh-negative women who are not isoimmunised will be administered Rh immunoglobulin to try to prevent isoimmunisation.
Read the full article on: Maternal isoimmunisation due to Rh incompatibility, what are the risks? ( 63).

Silvia Azaña Gutiérrez
B.Sc., M.Sc.
Graduate in Health Biology from the University of Alcalá and specialized in Clinical Genetics from the same university. Master in Assisted Reproduction by the University of Valencia in collaboration with IVI clinics.
License: 3435-CV