The Rh factor is an inherited protein found on the surface of red blood cells. Most people have this protein and are called Rh-positive. However, some people don't have protein; they are called Rh-negative. Rh-negative pregnant women are at risk of having a baby with a potentially dangerous form of anemia called Rh disease. Fortunately, treatment usually can prevent Rh disease.
Rh disease destroys fetal red blood cells. It once was a leading cause of fetal and newborn death. Without treatment, severely affected fetuses often are stillborn. In the newborn, Rh disease can result in jaundice (yellowing of the skin and eyes), anemia, brain damage, heart failure and death. It does not affect the mother’s health.
In the United States, about 15 percent of the white population, 5 to 8 percent of the African-American and Hispanic populations, and 1 to 2 percent of the Asian and Native American populations are Rh-negative (American College of Obstetricians and Gynecologists [ACOG], 2006; Moise, 2009). Being Rh-negative does not affect a person’s health in any way.
An Rh-negative mother and an Rh-positive father may conceive an Rh-positive baby. When this occurs, some of the fetus’s Rh-positive red blood cells may get into the mother’s bloodstream during pregnancy, labor and birth. Because red blood cells containing the Rh factor are foreign to the mother’s system, her body tries to fight them off by producing antibodies against them. This is called sensitization.
Once a woman becomes sensitized, her Rh antibodies can cross the placenta and destroy some of the red blood cells of an Rh-positive fetus. In a first pregnancy with an Rh-positive baby, there usually are no serious problems because the baby often is born before the mother is sensitized, or at least before the mother produces many Rh antibodies. However, a sensitized woman continues to produce Rh antibodies throughout her life. This means that in a second or later pregnancy, an Rh-positive baby is at risk for more severe Rh disease.
A simple blood test can tell if a woman is Rh-negative. Every woman should be tested at her first prenatal visit, or before pregnancy, to find out if she is Rh-negative. Another blood test can show if an Rh-negative woman has become sensitized.
An unsensitized Rh-negative pregnant woman can be treated with injections (shots) of a purified blood product called Rh immune globulin (RhIg) to prevent sensitization. She most likely receives RhIg at 28 weeks of pregnancy and again within 72 hours of giving birth if a blood test shows that her baby is Rh-positive (ACOG, 1999). She does not need an injection after delivery if her baby is Rh-negative. Some health care providers recommend an additional RhIg injection if a woman’s pregnancy goes past her due date (ACOG, 1999; Moise, 2008).
An Rh-negative woman should be treated with RhIg after any situation in which the fetal red blood cells can mix with her blood, including (ACOG, 1999; Moise, 2008):
An Rh-negative woman does not need treatment with RhIg if blood tests show that the baby’s father is Rh-negative (ACOG, 1999). If the father is Rh-negative, the baby is Rh-negative. An Rh-negative baby is not at risk of Rh disease.
It is not known exactly how RhIg works. It contains antibodies to the Rh factor that may prompt certain immune cells to clear Rh-positive cells from the mother’s circulation. As a result, she may not produce her own antibodies against fetal Rh-positive cells (Moise, 2008).
Protection by RhIg lasts only about 12 weeks (ACOG, 1999). An Rh-negative woman must be treated during each pregnancy.
Proper treatment with RhIg can prevent sensitization in almost all unsensitized Rh-negative women (ACOG, 1999). However, RhIg does not work for an Rh-negative woman who already is sensitized. The main reason Rh-negative women become sensitized is that they do not receive treatment when they need it, such as after an unrecognized miscarriage.
No. Even if a woman has no symptoms and stays healthy, she can continue to produce antibodies as part of her blood. If she has any more Rh-positive babies, they could develop Rh disease.
The baby’s father can have a blood test to see whether he is Rh-positive or Rh-negative. If the father is Rh-negative, the baby is not at risk of Rh disease, and the pregnant woman does not need any special tests or treatment.
If the father is Rh-positive (or if his Rh status is not known), the health care provider usually offers a sensitized pregnant woman a test called amniocentesis to determine whether the baby is Rh-positive or Rh-negative. Even if the father is Rh-positive, he may carry an Rh-negative gene. The baby has a 50-percent chance of inheriting the Rh-negative gene, so he has a 50-percent chance of being Rh-negative. During amniocentesis, the doctor inserts a needle into a woman’s abdomen to withdraw a small amount of amniotic fluid for testing. Amniocentesis poses a very small risk of miscarriage.
A new maternal blood test appears to be highly accurate in determining whether the fetus is Rh-positive or negative (5). This blood test was recently introduced in the United States and may soon reduce the need for amniocentesis (Van der Schoot, Hahn & Chitty, 2008).
If the fetus is Rh-positive (or if the fetal Rh status is unknown), the health care provider measures the levels of antibodies in the mother’s blood as pregnancy progresses. If she develops high levels of antibodies, the provider recommends tests that can help determine if the baby is developing Rh disease.
Most major medical centers offer an examination with a special form of ultrasound, called Doppler ultrasound, to determine if the fetus is developing anemia and how severe it may be. This test, which is repeated every 1 to 2 weeks, measures the speed of blood flowing through an artery in the fetus. It poses no risk to the fetus. Doppler ultrasound has reduced the need for amniocentesis to monitor fetuses at risk of Rh disease. A 2006 study reported that a Doppler ultrasound is more accurate than amniocentesis in detecting anemia (Oepkes, 2006). However, this test is not yet available everywhere. Women who do not live near a medical center that offers Doppler ultrasound can still be monitored with amniocentesis, which must be repeated every 10 days to 2 weeks.
If Doppler ultrasound or amniocentesis shows that the fetus may be developing severe anemia, the health care provider may recommend another test called cordocentesis. In this test, the doctor inserts a thin needle through the mother’s abdomen, guided by ultrasound, into a tiny blood vessel in the umbilical cord to take a blood sample from the fetus. This test poses a small risk of miscarriage.
If the fetus is near term and tests show that the baby is developing anemia, the health care provider may recommend inducing labor early, before the mother’s antibodies destroy too many fetal blood cells. After birth, if the baby has jaundice, he may be placed under special blue lights (phototherapy). In some cases, the baby may need a blood transfusion. Some cases of Rh disease are so mild that the baby does not need any treatment.
About 10 percent of fetuses with Rh disease develop severe anemia, which in the past was usually fatal (Mari et al., 2000). Today these fetuses can be treated in the uterus as early as 18 weeks gestation with blood transfusions, which are given using cordocentesis. About 90 percent of treated babies now survive (Moise, 2008).
Although RhIg is a blood product, there is minimal to no risk of contracting HIV or hepatitis from it (ACOG, 1999). The donated blood is screened for HIV and hepatitis and treated with a substance that kills viruses and bacteria.
- American College of Obstetricians and Gynecologists (ACOG). (1999). Prevention of RhD alloimmunization (Practice Bulletin No. 4). Washington, D.C.: Author.
- American College of Obstetricians and Gynecologists (ACOG). (2006). Management of alloimmunization during pregnancy. (Practice Bulletin No. 75). Washington, D.C.: Author.
- Lenetix Medical Screening Laboratory. RhD genotyping. Retrieved September 11, 2009 from: http://www.lenetix.com./html/rhd__sry_genotyping.html.
- Mari, G., et al. (2000). Noninvasive diagnosis by Doppler ultrasonography of fetal anemia due to maternal red-cell alloimmunization. New England Journal of Medicine, 342(1), 9-14.
- Moise, K.J. (2008). Management of Rh immunization in pregnancy. Obstetrics and Gynecology, 112(1), 164-176.
- Moise, K.J. (2009). Hemolytic disease of the fetus and newborn. In Creasy, R.K., et al (eds.), Creasy and Resnik’s maternal-fetal medicine principles and practice (6th ed., pages 477-503). Philadelphia: Saunders Elsevier.
- Oepkes, D. (2006). Doppler ultrasonography versus amniocentesis to predict fetal anemia. New England Journal of Medicine, 355(2), 156-164.
- Van der Schoot, C.E., Hahn, S. & Chitty, L.S. (2008). Non-invasive prenatal diagnosis and determination of fetal Rh status. Seminars in Fetal and Neonatal Medicine, 13, 63-68.
Frequently Asked Questions
Can dad's exposure to chemicals harm his future kids?
Dad's exposure to harmful chemicals and substances before conception or during his partner's pregnancy can affect his children. Harmful exposures can include drugs (prescription, over-the-counter and illegal drugs), alcohol, cigarettes, cigarette smoke, chemotherapy and radiation. They also include exposure to lead, mercury and pesticides.
Unlike mom's exposures, dad's exposures do not appear to cause birth defects. They can, however, damage a man's sperm quality, causing fertility problems and miscarriage. Some exposures may cause genetic changes in sperm that may increase the risk of childhood cancer. Cancer treatments, like chemotherapy and radiation, can seriously alter sperm, at least for a few months post treatment. Some men choose to bank their sperm to preserve its integrity before they receive treatment. If you have a question about a specific exposure, contact the Organization of Teratology Information Specialists at www.otispregnancy.org.
Can Rh factor affect my baby?
The Rh factor may be a problem if mom is Rh-negative but dad is Rh-positive. If dad is Rh-negative, there is no risk.
If your baby gets her Rh-positive factor from dad, your body may believe that your baby's red blood cells are foreign elements attacking you. Your body may make antibodies to fight them. This is called sensitization.
If you're Rh-negative, you can get shots of Rh immune globulin (RhIg) to stop your body from attacking your baby. It's best to get these shots at 28 weeks of pregnancy and again within 72 hours of giving birth if a blood test shows that your baby is Rh-positive. You won't need anymore shots after giving birth if your baby is Rh-negative. You should also get a shot after certain pregnancy exams like an amniocentesis, a chorionic villus sampling or an external cephalic version (when your provider tries to turn a breech-position baby head down before labor). You'll also want to get the shot if you have a miscarriage, an ectopic pregnancy or suffer abdominal trauma.
Does cleft lip or cleft palate cause dental problems?
A cleft lip or cleft palate that extends into the upper gums (where top teeth develop) can cause your baby to have certain dental problems, including:
- Missing teeth
- Too many teeth
- Oddly shaped teeth
- Teeth that are out of position around the cleft
Every baby with a cleft lip or palate should get regular dental checkups by a dentist with experience taking care of children with oral clefts. Dental problems caused by cleft lip or palate usually can be fixed. If needed, your baby can get ongoing care by a team of experts, including:
- A dentist
- An orthodontist to move teeth using braces
- An oral surgeon to reposition parts of the upper jaw, if needed, and to fix the cleft
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause ear problems?
Cleft lip does not cause ear problems.
Babies with cleft palate, however, are more likely than other babies to have ear infections and, in some cases, hearing loss. This is because cleft palate can cause fluid to build up in your baby’s middle ear. The fluid can become infected and cause fever and earache. If fluid keeps building up with or without infection, it can cause mild to moderate hearing loss.
Without treatment , hearing loss can affect your baby’s language development and may become permanent.
With the right care, this kind of hearing loss is usually temporary. Your baby’s provider may recommend:
- Having your baby’s ears checked regularly for fluid buildup
- Medicines for treating fluid buildup and ear infections
- Ear tubes if your baby has fluid in his ears over and over again. Ear tubes are tiny tubes that are inserted into the eardrum to drain the fluid and help prevent infections.
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause problems with breastfeeding?
Babies with only a cleft lip usually don’t have trouble breastfeeding. Most of the time, they can breastfeed just fine. But they may need some extra time to get started.
Babies with cleft lip and palate or with isolated cleft palate can have:
- Trouble sucking strong enough to draw milk through a nipple
- Problems with gagging or choking
- Problems with milk coming through the nose while feeding
Most babies with cleft palate can’t feed from the breast. If your baby has cleft palate, he can still get the health benefits of breastfeeding if you feed him breast milk from a bottle. Your provider can show you how to express (pump) milk from your breasts and store breast milk.
Your baby’s provider can help you start good breastfeeding habits right after your baby is born. She may recommend:
- Special nipples and bottles that can make feeding breast milk from a bottle easier
- An obturator. This is a small plastic plate that fits into the roof of your baby’s mouth and covers the cleft opening during feeding.
See also: Cleft lip and cleft palate, Breastfeeding
Does cleft lip or cleft palate cause speech problems?
Children with cleft lip generally have normal speech. Children with cleft lip and palate or isolated cleft palate may:
- Develop speech more slowly
- Have a nasal sound when speaking
- Have trouble making certain sounds
Most children can develop normal speech after having cleft palate repair. However, some children may need speech therapy to help develop normal speech.
See also: Cleft lip and cleft palate
What are choroid plexus cysts?
The choroid plexus is the area of the brain that produces the fluid that surrounds the brain and spinal cord. This is not an area of the brain that involves learning or thinking. Occasionally, one or more cysts can form in the choroid plexus. These cysts are made of blood vessels and tissue. They do not cause intellectual disabilities or learning problems. Using ultrasound, a health care provider can see these cysts in about 1 in 120 pregnancies at 15 to 20 weeks gestation. Most disappear during pregnancy or within several months after birth and are no risk to the baby. They aren't a problem by themselves. But if screening tests show other signs of risk, they may indicate a possible genetic defect. In this case, testing with higher-level ultrasound and/or amniocentesis may be recommended to confirm or rule out serious problems.
What if I didn't take folic acid before pregnancy?
If you didn’t take folic acid before getting pregnant, it doesn't necessarily mean that your baby will be born with birth defects. If women of childbearing age take 400 micrograms of folic acid every day before and during early pregnancy, it may help reduce their baby’s risk for birth defects of the brain and spin called neural tube defects (NTDs). But it only works if you take it before getting pregnant and during the first few weeks of pregnancy, often before you may even know you’re pregnant.
Because nearly half of all pregnancies in the United States are unplanned, it's important that all women of childbearing age (even if they're not trying to get pregnant) get at least 400 micrograms of folic acid every day. Take a multivitamin with folic acid before pregnancy. During pregnancy, switch to a prenatal vitamin, which should have 600 micrograms of folic acid.
Last reviewed November 2012