From the Guidelines
No, if both parents are Rh negative, their baby cannot be Rh positive. This is because the Rh factor is determined by genetics, specifically by the presence or absence of the Rh D antigen on red blood cells, as discussed in the context of RhD immune globulin administration 1. The Rh factor is inherited in a dominant pattern, meaning a person needs only one copy of the Rh positive gene to have Rh positive blood. When both parents are Rh negative, they each have two copies of the recessive Rh negative gene (dd) and cannot pass a dominant Rh positive gene (D) to their child. Therefore, their child will inherit one recessive gene from each parent, resulting in Rh negative blood type (dd). This genetic principle is consistent across all pregnancies between two Rh negative parents, so there is no possibility of having an Rh positive child in this scenario. Some key points to consider in this context include:
- The use of RhD immune globulin (RhIg) to prevent RhD alloimmunization in RhD-negative pregnant individuals, as discussed in 1.
- The mechanism of action of RhIg in suppressing the maternal immune response to nonself D-antigen, although not fully understood, as noted in 1.
- The recommendations from various organizations, such as the Society for Maternal-Fetal Medicine (SMFM) and the World Health Organization (WHO), regarding RhD testing and RhIg administration in different scenarios, including abortion care 1. However, these points do not alter the fundamental genetic principle that determines the Rh blood type of a child based on the parents' Rh status.
From the FDA Drug Label
If the father can be determined to be Rho(D) negative, HyperRHO S/D Full Dose need not be given
- The baby can be Rh positive if the father is Rh positive, but the text does not directly state what happens when both parents are Rh negative.
- However, it can be inferred that if both parents are Rh negative, they can only pass on Rh negative genes to their offspring, making it unlikely for the baby to be Rh positive.
- But the provided text does not directly answer the question, and the information about the father being Rh negative is used to determine if the mother needs the HyperRHO S/D Full Dose, not to determine the baby's Rh status.
- Therefore, based on the provided information, no conclusion can be drawn about the baby's Rh status when both parents are Rh negative 2.
From the Research
Rh Blood Type Inheritance
- The Rh blood type is determined by the presence or absence of the RhD antigen on red blood cells.
- A person can be either Rh-positive (has the RhD antigen) or Rh-negative (does not have the RhD antigen).
- The inheritance of Rh blood type is controlled by two genes, one from each parent.
Possible Rh Blood Type of the Baby
- If both parents are Rh-negative, they can only pass on Rh-negative genes to their offspring.
- Therefore, the baby will always be Rh-negative, as there is no possibility of inheriting an Rh-positive gene from either parent 3.
- However, it is essential to note that Rh immune globulin (RhIG) may be administered to Rh-negative mothers to prevent the formation of anti-D alloantibodies, which can affect future pregnancies 4.
Determining the Baby's Rh Blood Type
- The baby's Rh blood type can be determined by testing the baby's blood after birth.
- If the baby is Rh-positive, the mother may be given RhIG to prevent the formation of anti-D alloantibodies 3.
- It is crucial to follow the guidelines for RhIG administration to minimize the risk of Rh alloimmunization and ensure the best possible outcomes for the mother and future pregnancies.