American Medical Association Family Medical Guide - American Medical Association [276]
Vaccinations Before Pregnancy
If you are not sure if you have been vaccinated against rubella or measles or had chickenpox during childhood, ask your doctor about having a blood test before you become pregnant to determine if you are immune to these diseases. If the test shows that you have not had these infections (and you definitely are not pregnant), you still can be immunized. You should then wait at least 3 months before getting pregnant because the risk of heart defects in the fetus caused by these viruses is greatest in the first 3 months of pregnancy.
Cytomegalovirus
Cytomegalovirus is an infection that usually causes no symptoms; most people have had the infection and have not known it. However, if a pregnant woman is infected during pregnancy, especially during the first trimester, the virus can be transmitted to the fetus and can cause birth defects such as blindness or mental retardation, or can be fatal. Still, only a small percentage of babies who are born with the infection have any problems. If you think you may have been exposed to an infected person during your pregnancy, or if you have a flulike illness during pregnancy, see your doctor.
Toxoplasmosis
Toxoplasmosis (see page 940) is an infection caused by a parasite that lives in raw meat and in some animals, including cats. Although the infection causes only flulike symptoms in adults, it can infect a fetus and cause severe birth defects or can be fatal. If you have a cat, your doctor will recommend having a test to see if you are immune to toxoplasmosis. If you are immune, your fetus cannot become infected. If you are not immune, your doctor will tell you what precautions to take to avoid infection, such as not changing the cat’s litter box, wearing gloves when gardening, and washing fruits and vegetables before eating them.
Rh Incompatibility
Rh (Rhesus) incompatibility is a mismatch between the blood of the pregnant woman and the blood of the fetus. Rh incompatibility occurs only when the mother’s blood is Rh negative and the fetus’s blood is Rh positive. Complications from Rh incompatibility are rare because it is usually diagnosed and treated immediately with a blood product called Rh immunoglobulin, which is given to the pregnant woman to prevent her immune system from attacking the fetus’s blood.
The blood of an Rh-positive fetus may enter the bloodstream of an Rh-negative woman anytime during the pregnancy but usually occurs at birth. Recognizing the Rh-positive blood as a foreign substance, the mother’s immune system produces antibodies to attack the Rh-positive red blood cells. This is usually not a problem for a first Rh-positive fetus because the number of antibodies produced initially is not great enough to harm the fetus. However, if the woman does not receive the Rh immunoglobulin, her body will continue to produce antibodies against Rh-positive blood. If she has a fetus with Rh-positive blood in a subsequent pregnancy, the antibodies will attack the fetus’s red blood cells, possibly causing a potentially fatal (to the fetus) form of Rh incompatibility called hydrops fetalis. If the fetus does not die before birth, after birth a child can develop symptoms of hydrops fetalis such as anemia, heart failure, severe swelling, and respiratory distress.
The Rh immunoglobulin is usually given at about the 28th week of pregnancy and again within 72 hours of delivery. In addition to preventing the mother’s immune system from producing antibodies to Rh-positive blood, the immunoglobulin destroys any red blood cells from the fetus that may have entered her circulation before her body started developing antibodies. If the mother’s antibodies have begun to destroy the fetus’s red blood cells, a doctor may induce labor if the pregnancy is close to term. If the fetus is not mature enough to be delivered, a fetal blood transfusion may be given inside