When the inherited blood types of mother and fetus differ, the most common cause of difficulties is

Amniocentesis: A procedure in which amniotic fluid and cells are taken from the uterus for testing. The procedure uses a needle to withdraw fluid and cells from the sac that holds the fetus.

Anemia: Abnormally low levels of red blood cells in the bloodstream. Most cases are caused by iron deficiency (lack of iron).

Antibodies: Proteins in the blood that the body makes in reaction to foreign substances, such as bacteria and viruses.

Breech Presentation: A position in which the feet or buttocks of the fetus would appear first during birth.

Cells: The smallest units of a structure in the body. Cells are the building blocks for all parts of the body.

Chorionic Villus Sampling (CVS): A procedure in which a small sample of cells is taken from the placenta and tested.

Ectopic Pregnancy: A pregnancy in a place other than the uterus, usually in one of the fallopian tubes.

Fetus: The stage of human development beyond 8 completed weeks after fertilization.

Genes: Segments of DNA that contain instructions for the development of a person's physical traits and control of the processes in the body. They are the basic units of heredity and can be passed from parent to child.

Induced Abortion: An intervention to end a pregnancy so that it does not result in a live birth.

Jaundice: A buildup of bilirubin (a brownish yellow substance formed from the breakdown of red cells in the blood) that causes the skin to have a yellowish appearance.

Miscarriage: Loss of a pregnancy that is in the uterus.

Obstetrician–Gynecologist (Ob-Gyn): A doctor with special training and education in women's health.

Oxygen: An element that we breathe in to sustain life.

Placenta: An organ that provides nutrients to and takes waste away from the fetus.

Prenatal Care: A program of care for a pregnant woman before the birth of her baby.

Rh Factor: A protein that can be found on the surface of red blood cells.

Rh Immunoglobulin (RhIg): A substance given to prevent an Rh-negative person's antibody response to Rh-positive blood cells.

Trimester: A 3-month time in pregnancy. It can be first, second, or third.

Ultrasound Exams: Tests in which sound waves are used to examine inner parts of the body. During pregnancy, ultrasound can be used to check the fetus.

Umbilical Cord: A cord-like structure containing blood vessels. It connects the fetus to the placenta.

Uterus: A muscular organ in the female pelvis. During pregnancy, this organ contains and nourishes the fetus.

What causes blood type incompatibility?

Blood type and factors are determined by genetics. A baby may have the blood type and Rh factor of either parent, or a combination of both parents. The Rh positive gene is dominant (stronger) and even when paired with an Rh negative gene, the positive gene takes over.

Blood type incompatibility only becomes a problem after a mother develops antibodies against her baby’s blood cells. These antibodies don’t develop until a mother is “sensitized,” which occurs when the mother’s and baby’s blood mix during pregnancy. This can happen if the baby’s blood crosses the placenta or during certain invasive prenatal tests, trauma, birth or other situations. Although sensitization is not a common issue in first pregnancies, it can cause complications with future pregnancies.

Prenatal diagnosis of blood type incompatibility

Early identification of antibodies is important, and all pregnant women receive a blood test early in their pregnancy. If antibodies are present, then prenatal diagnostic procedures may include:

• ultrasound to evaluate blood flow in the baby’s brain, which can be used to detect early anemia before evidence of hydrops
• ultrasound to detect organ enlargement or fluid buildup in the baby
• blood tests to monitor the levels of the mother’s antibodies to determine the baby’s risk of anemia
• sampling of blood from the fetal umbilical cord to check for anemia

Specialists you will work with

In addition to your regular OB, a maternal fetal medicine specialist will help monitor and manage any issues related to blood type incompatibility during your pregnancy. If your baby requires special care after birth, your care team may include a neonatologist in the neonatal intensive care unit (NICU).

How does blood type incompatibility affect my baby?

As the mother’s antibodies destroy the baby’s red blood cells, the baby can become anemic. The anemia can cause other complications, including:

• jaundice — yellowing of the skin, eyes and mucous membranes
• enlargement of the liver and spleen
• hydrops fetalis — this occurs when the baby’s organs are unable to handle the anemia. The baby’s heart begins to fail and large amounts of fluid build up in the fetal tissues and organs. A fetus with hydrops fetalis is at great risk of being stillborn.

After birth, the red blood cell destruction may continue, leading to a condition called hemolytic disease of the newborn (HDN). Problems may include:

• severe jaundice — when the baby’s liver is unable to handle the large amount of bilirubin that results from red blood cell breakdown, the baby's liver becomes enlarged, and the anemia continues.
• kernicterus — the most severe form of excess bilirubin can lead to build up of bilirubin in the brain, possibly causing seizures, brain damage, deafness and death.

Does my baby need a special hospital?

That depends on the severity of your baby’s condition. If you deliver at Froedtert, your baby will receive top-notch care in Children’s Wisconsin's Level IV Neonatal Intensive Care Unit, which is ranked as one of the best in the nation. Your baby will stay in the hospital until he or she is well enough to go home.

How does blood type incompatibility affect my pregnancy?

You may need frequent blood tests to follow the amount of antibodies you’re making and regular ultrasounds to monitor your baby more closely. Most Milwaukee-area patients continue to receive care at the Fetal Concerns Center and then deliver at the Froedtert & the Medical College of Wisconsin Birth Center, though in some cases it’s possible for mothers to receive follow-up care and deliver at another hospital closer to home. If your baby’s condition worsens, you may need to deliver early.

If an Rh negative mother has not yet been sensitized, she is usually given Rh immunoglobulin (RhIg), also known as RhoGAM. This blood product can prevent the mother’s antibodies from reacting to Rh-positive cells. Many women are also given RhIg around the 28th week of pregnancy. After the baby is born, a woman should receive a second dose of the drug within 72 hours.

How do you treat blood type incompatibility?

Fortunately, hemolytic disease of the newborn is a very preventable disease. Treatment will be informed by the medical team’s assessment of your baby’s condition and your input as the parent, and it could include:

• fetal intrauterine transfusion of red blood cells — this procedure places a needle through the mother’s uterus and directly into the umbilical cord vein or baby’s abdominal cavity to replenish depleted red blood cells. This can help prevent a baby’s anemia from progressing into hydrops. Intrauterine transfusions may need to be repeated, and your baby may require another transfusion immediately after birth.
• early delivery — if the baby develops complications and has mature lungs, your doctor may recommend inducing labor and delivery to prevent worsening of the disease.

Will I be able to help care for my baby?

Yes. Our recently expanded and redesigned NICU was created to promote family bonding, with private rooms where parents can stay with their baby 24/7, and other special features for families’ comfort. Our on-call lactation specialists can help you successfully breastfeed and pump and store breast milk when direct breastfeeding isn’t an option.

When can my baby go home?

Your baby will be discharged from the hospital once he or she is breathing independently, eating well and gaining weight. That may take several weeks. Premature babies will likely require a longer NICU stay.

What’s my baby’s long-term prognosis?

Although outcomes depend on the severity of your baby’s condition, babies affected by blood type incompatibility generally do very well. Babies who have not yet developed hydrops have survival rates greater than 90 percent, and even the majority of babies with hydrops survive after fetal intrauterine transfusion.

What about future pregnancies?

The mother’s immune system keeps the antibodies in case the foreign cells appear again, even in a future pregnancy. Complications are usually more severe in subsequent pregnancies than they are in the first. If an Rh negative mother receives Rhlg before becoming Rh sensitized, it helps protect a future Rh positive baby.