Blood Type and Rh Factor - What Do They Mean

Blood Type, Rh and Sperm Donors

When choosing a donor, most people don't have to worry about their sperm donor's blood type, unless their goal is to have a baby with a blood type that matches their's or their spouses. If a woman is Rh positive, e.g. A+, O+, B+ or AB+, she doesn't have to worry about blood type at all. If a woman is Rh-, she should consult with her doctor before choosing a donor to discuss possible issues that might come up if she's considering an Rh+ sperm donor.

A, B, O, and AB are the main categories of blood with which most people are familiar. Each blood type is further categorized by the presence (positive) or absence (negative) of antigens in the blood, called the Rh factor (Rhesus factor, named after the kind of monkey first tested for the Rh factor). People who have the Rhesus factor are Rh-positive, so someone with the blood type O who has Rh antigens has O+ blood.

Rh+ people are the most common type. People with no Rhesus factor (people that don't have the antigen in their blood) are considered Rh-.

A blood type's Rh factor is usually considered important with regards to pregnancy, where an  Rh+ baby born to an Rh- mother runs the risk of developing Rh disease. Only Rh- women risk having a baby born with the Rhesus factor disease; Rh+ women do not.

If a Woman is Rh-

To conceive an Rh+ baby, an Rh- mother needs to have been with an Rh+ man. An Rh+ man has a 50 percent chance of passing on his Rh+ blood type to a baby he fathers.

The Rhesus factor is less likely to affect a woman's first baby because the woman's blood will have had less time to produce the antibodies to fight off the antigens in the baby's  blood. If the woman's immune system responds by producing antibodies, those antibodies will be present in her body for  life. Thus, different Rh factor types between a woman and her baby may increase the potential for Rh disease in each following pregnancy.

If the mother is Rh- and the baby is Rh+, and the baby's blood enters the woman's bloodstream during pregnancy, labor, or delivery, the woman's immune method may respond by producing antibodies to fight off the baby's antigens. This incompatibility won't affect the health of the mother but it can affect the baby's health. Potential health problems include jaundice, anemia, brain or heart dysfunction ands in serious cases, fatality.

Preventative measures are available to protect against Rhesus factor. Women should get tested early in their first pregnancy to determine if they are Rh- and whether they are sensitized. Sensitization (when a woman's bodies produces antibodies) may occur anytime a woman and her baby's blood mix. This includes blood tranfusions,normal pregnancy, ectopic pregnancies and miscarriages.

If a woman is Rh- and has not yet been sensitized, she may be injected with a blood product known as Rh immunoglobulin (Rhlg) six months into her pregnancy. This should prevent sensitization for the rest of the pregnancy. The Rhlg shot seeks to destroy any antigens present in the bloodstream before the mother can generate antibodies.

Newborns are reccomended to be tested for their Rhesus blood type. If the baby is Rh+, the mother may receive another Rhlg shot soon after birth to prevent her from sensitization. Rhlg injections only last for a given pregnancy so later pregnancies may need separate Rhlg injections.