Rh Incompatibility and Other Blood Group Issues | OB-GYN


Rh Incompatibility and Other Blood Group Issues

Our nationally ranked OB-GYN program provides attentive monitoring and care for Rh incompatibility and other maternal-fetal conditions during pregnancy.

Medically reviewed by Laila Rhee, M.S. on Oct. 16, 2023.

Pregnant woman sitting on an exam table holding her belly while talking to health care professional.

Trusted Care for Blood Type Incompatibilities

Our specialists at UC Davis Health are prepared to care for you and your baby in the event of blood type incompatibility. Trust us to use our expertise to diagnose and treat you and your child.


What Is Blood Type Incompatibility?

People typically have one of four blood types: A, B, AB or O. Health care providers also classify blood types as positive or negative. For example, your blood type could be type A-negative (A-) or type O-positive (O+).

The presence of a protein (Rh factor) on your red blood cells determines whether your blood type is positive or negative. People with the protein are Rh-positive; those without the protein are Rh-negative.

Blood type incompatibility during pregnancy means that you and your unborn baby have different blood types. As a result, your immune system may react to your unborn baby’s blood type. It may attack your unborn baby’s red blood cells, which can lead to serious problems.

ABO incompatibility is a maternal-fetal blood group problem that can develop during pregnancy. Usually, the mother has type O blood, and her unborn baby has type A, B or AB blood.

Rh incompatibility (also called Rhesus disease) is another blood type issue that may impact your pregnancy. Most people (about 85%) are Rh-positive. But if you are Rh-negative and your unborn baby is Rh-positive, problems may develop during that pregnancy or future pregnancies.

People with blood type incompatibility need treatment during pregnancy to prevent complications. 



Rh incompatibility may not cause problems if you receive treatment before antibodies develop. But left untreated, the condition can lead to dangerous pregnancy complications and fetal conditions such as hemolytic disease of the newborn (HDN). HDN is a blood disorder that affects newborns.

Potential Complications

Blood group incompatibility can lead to these problems in fetuses and newborns:

  • Fetal anemia (low red blood cell count)
  • Jaundice (yellow skin and whites of eyes)
  • Enlarged liver or spleen
  • Abnormal heart rate
  • Breathing problems
  • Organ damage
  • Heart failure
  • Miscarriage

Causes and Risk Factors of Rh Incompatibility and Other Blood Group Issues

You inherit your blood type, meaning it’s passed down to you from your mother or father. Blood type incompatibility occurs when you have a different blood type than the baby developing in your womb.

If incompatible blood types mix during pregnancy, your immune system makes antibodies that attack your baby’s blood cells. This reaction, called Rh sensitization, is similar to how your body protects itself from illnesses or allergens.

A mother and baby’s blood mix during labor and delivery. So these antibodies usually don’t develop until after birth. Incompatibility problems are more likely to occur during a second pregnancy because the antibodies are already present.

Left untreated, Rh or ABO incompatibility during pregnancy can be very dangerous for an unborn baby or newborn. The mother’s antibodies attack the baby’s red blood cells and deprive the baby of oxygen, which can be life-threatening.

There are some risk factors for blood incompatibility, including:

Being Rh-Negative

Most fetuses are Rh-positive. So if you are Rh-negative, your risk of Rh incompatibility is high. That’s why it’s important to know your blood type and Rh status. Talk to your OB-GYN about your risk before getting pregnant or as early in your pregnancy as possible.

Prenatal Screening Tests

In some cases, a mother and her unborn baby’s blood mix during invasive prenatal testing and screening. These tests include amniocentesis and chorionic villus sampling (CVS). Amniocentesis and CVS determine the fetus’s risk of a genetic disease by taking samples of amniotic fluid or placental tissue.

Miscarriage, Ectopic Pregnancy or Abortion

If you are Rh-negative and lose or stop a pregnancy, your body still has a chance to produce Rh antibodies. As a result, your risk of blood type incompatibility in a future pregnancy is higher.


Diagnosing Rh and Blood Type Incompatibility

An Rh factor test determines whether you are Rh-positive or negative. It is a simple blood test you receive at the beginning of your pregnancy, usually at your first prenatal care visit.

If you are Rh-negative, your provider will talk to you about when you should begin treatment to prevent antibodies. Your provider may also recommend other antibody screening tests throughout your pregnancy.

If antibodies are present, you might need extra blood tests and ultrasounds during your pregnancy to monitor your baby’s health. At UC Davis Health, we have specialized expertise evaluating and monitoring Rh compatibility and other types of high-risk pregnancies. Our team provides the care needed to keep your unborn baby as healthy as possible.

Treatments for Rh Incompatibility and Other Blood Group Disorders

At UC Davis Health, experts across several disciplines work together to safeguard the health of you and your baby. You receive seamlessly coordinated care from top obstetricians, maternal-fetal medicine specialists and neonatologists (newborn specialists).

Treatments for blood type incompatibility may include:

Rh Immunoglobulin

Rh immunoglobulin (Rhlg) is the most common treatment to prevent antibody production in people who are Rh-negative. You receive this medication as a shot at around 28 weeks of pregnancy and right after you deliver your baby. You may also need Rhlg after a prenatal screening test or if you have a miscarriage or abortion. Rh immunoglobulin won’t help if your body has already produced antibodies.

Blood Transfusion or Exchange

If your body produces antibodies and fetal anemia develops, your unborn baby may need a blood transfusion. During a fetal blood transfusion or exchange, we replace damaged red blood cells with healthy cells from a donor. Your baby receives the blood cells through their umbilical cord. Some babies also need blood transfusions soon after birth.


Some newborns with ABO incompatibility receive phototherapy for jaundice. Phototherapy uses specific types of light to lower bilirubin levels in their blood. Bilirubin is a substance that your body makes when it breaks down red blood cells. Bilirubin levels can get too high in babies with hemolytic disease and cause jaundice. Learn more about maternity services at our Women’s Center for Health.


Preventing Blood Type Incompatibility Complications

You can’t control your blood type or the blood type of your baby. But you can take measures to prevent Rh disease if you and your baby have incompatible blood types. If you are Rh-negative, seek treatment during your pregnancy to prevent antibodies from developing.

"Rh Factor Blood Type and Pregnancy," American Pregnancy Association, https://americanpregnancy.org/healthy-pregnancy/pregnancy-complications/rh-factor/

How common is it in the U.S.?

15%Of women are Rh-negative and at risk for Rh incompatibility during pregnancy

Source: American Pregnancy Association: Rh Factor Blood Type and Pregnancy

Request an Appointment

As Sacramento's No. 1 hospital, you'll benefit from unique advantages in primary care and specialty care. This includes prevention, diagnosis and treatment options from experts in 150 specialties.

Referring Physicians

To refer a patient, you can submit an electronic referral form or call.



For questions and appointment information

Awards and Recognitions
USNWR Best Hospital badge

Ranked among the nation’s best hospitals

A U.S. News & World Report best hospital in cancer, cardiology, heart & vascular surgery, diabetes & endocrinology, ENT, geriatrics, neurology & neurosurgery, obstetrics & gynecology, and pulmonology & lung surgery.

Learn more
US News & World Report best Children’s Hospital badge

Ranked among the nation’s best children’s hospitals

A U.S. News & World Report best children’s hospital in diabetes & endocrinology, nephrology, and orthopedics*. (*Together with Shriners Children’s)

Learn more
USNWR best regional hospital badge

Ranked Sacramento’s #1 hospital

Ranked Sacramento’s #1 hospital by U.S. News, and high-performing in COPD, colon cancer surgery, diabetes, heart attack, heart failure, hip fracture, hip replacement, kidney failure, leukemia, lymphoma & myeloma, lung cancer surgery, ovarian cancer surgery, pneumonia, prostate cancer surgery, stroke, TAVR, uterine cancer surgery, gastroenterology & GI surgery, and orthopedics.

Learn more
Magnet designation badge

The nation’s highest nursing honor

UC Davis Medical Center has received Magnet® recognition, the nation’s highest honor for nursing excellence.

Learn more
Chime acute badge

“Most Wired” for acute care

UC Davis Health has been recognized as a level 10 out of 10 in the Digital Health “Most Wired” program from the College of Healthcare Information Management Executives (CHIME). The honor recognizes excellence in using technology to improve the delivery of care.

Learn more
Chime ambulatory badge

“Most Wired” for ambulatory care

UC Davis Health has been recognized as a level 10 out of 10 in the Digital Health “Most Wired” program from the College of Healthcare Information Management Executives (CHIME). The honor recognizes excellence in using technology to improve the delivery of care.

Learn more
NCI badge

World-class cancer care

One of ~56 U.S. cancer centers designated “comprehensive” by the National Cancer Institute.

Learn more

A leader in health care equality

For the 11th consecutive year, UC Davis Medical Center has been recognized as a “Leader in LGBTQ+ Healthcare Equality.”

Learn more
See more