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Blood Types in Pregnancy

Blood Types in Pregnancy

About blood types

Every person has a blood type (O, A, B, or AB) and an Rh factor, either positive or negative. The blood type and the Rh factor simply mean that a person's blood has certain specific characteristics. The blood type is found as proteins on red blood cells and in body fluids. The Rh factor is a protein that is found on the covering of the red blood cells. If the Rh factor protein is present on the cells, the person is Rh-positive. If there is no Rh factor protein, the person is Rh- negative.

The following are the possible combinations of blood types with the Rh factors:

Blood Type

A

B

O

AB

Rh positive

A+

B+

O+

AB+

Rh negative

A-

B-

O-

AB-

Rh factors are genetically determined. A baby may have the blood type and Rh factor of either parent, or a combination of both parents. Rh factors follow a common pattern of genetic inheritance. The Rh-positive gene is dominant (stronger) and even when paired with an Rh-negative gene, the positive gene takes over.

  • If a person has the genes + +, the Rh factor in the blood will be positive.

  • If a person has the genes + -, the Rh factor will also be positive.

  • If a person has the genes - -, the Rh factor will be negative.

A baby receives one gene from the father and one from the mother. More specifically, consider the following:

Illustration of Rh factor: baby is ++Rh positive

If a father's Rh factor genes are + +, and the mother's are + +, the baby will have one + from the father and one + gene from the mother. The baby will be + + Rh positive.

 

Illustration of Rh factor: baby is +-Rh positive

If a father's Rh factor genes are + +, and the mother's are - -, the baby will have one + from the father and one - gene from the mother. The baby will be + - Rh-positive.

 

Illustration of Rh factor: baby is ++Rh positive, +-Rh negative, or --Rh negative

If the father's genes are + - Rh-positive, and the mother's are + - Rh-positive, the baby can be:

  • + + Rh-positive

  • + - Rh-positive

  • - - Rh-negative

 

Illustration of Rh factor: baby is +-Rh negative or --Rh positive

If the father's genes are - -, and the mother's are + -, the baby can be

  • + - Rh-positive

  • - - Rh-negative

 

Illustration of Rh factor: baby is --Rh negative

If the father's genes are - -, and the mother's are - -, the baby will be:

  • - - Rh-negative

Problems with the Rh factor occur when the mother's Rh factor is negative and the baby's is positive. Sometimes, an incompatibility may occur when the mother is blood type O and the baby is either A or B.

Reviewed Date: 09-28-2014

Grupos Sanguíneos en el Embarazo

Disclaimer: This information is not intended to substitute or replace the professional medical advice you receive from your child's physician. The content provided on this page is for informational purposes only, and was not designed to diagnose or treat a health problem or disease. Please consult your child's physician with any questions or concerns you may have regarding a medical condition.