$Unique_ID{PAR00426}
$Pretitle{}
$Title{Pregnancy:  The Sixth Month:  Ask the Doctor}
$Subtitle{}
$Author{
Editors of Consumer Guide
Ellis, Jeffrey W
Ellis, Maria}
$Subject{Sixth Month Ask Doctor Rh Incompatibility antibody antibodies
sensitized anemia heart failure stillbirth RhO (D) immune globulin Rh-negative
Rh-positive abortion miscarriage miscarriages ectopic pregnancy blood test
Visit Visits}
$Log{
Rh Incompatibility*0042601.tif}

Miracle of Birth


The Sixth Month:  Ask the Doctor


Should I Worry About Rh Incompatibility?


     Once a leading cause of death in babies throughout the world, Rh
incompatibility can now be prevented through routine prenatal blood testing
and the use of certain drugs.
     Another area in which rapid advances in obstetrics have led to more
healthy newborn babies is Rh incompatibility.  Once a disease that was a
leading cause of death in babies throughout the world, Rh incompatibility can
now be easily prevented through routine prenatal blood testing and the use of
certain drugs.

What is the Rh Factor?

     Approximately 87 percent of white persons and 93 percent of black persons
are born with a substance on their blood cells known as the Rh factor, so
called because a similar substance is found on the blood cells of rhesus
monkeys.  Individuals who have this factor on their blood cells are called Rh
positive; those without it are called Rh negative.  The presence of the Rh
factor is inherited from one's parents.

When Does the Rh Factor Cause Problems?

     The genes that a baby receives from his parents at conception dictate
whether or not he will be Rh positive or Rh negative.  Normally, during labor
and delivery, some of the baby's blood will escape from the placenta and enter
the mother's blood.  If both the mother and the fetus are Rh positive or if
both are Rh negative, this leakage of fetal blood will cause no problems.
     If the mother's blood is Rh negative and the baby's blood is Rh positive
(the baby would have received the gene for the Rh factor from his father),
however, a problem can occur.  When the baby's Rh-positive blood enters the
mother's Rh-negative blood during delivery, the mother's blood considers the
baby's Rh factor to be a foreign substance.  The mother's body then begins to
form antibodies to get rid of this foreign substance.
     Antibodies are normally formed in the body in response to foreign
substances--usually bacteria and viruses that may be harmful.  These
antibodies act by destroying the foreign substance, thus protecting the body
against their harmful effects.  A person who forms antibodies against a
particular substance is called "sensitized" to that substance.
     When an Rh-negative mother gives birth to her first Rh-positive baby,
she is likely to become sensitized to the Rh factor.  That first Rh-positive
baby is usually unaffected.
     However, the mother's body keeps the antibodies against Rh-positive blood
for life.  If she becomes pregnant with an Rh-positive baby again, this
fetus may be affected.  During this subsequent pregnancy, the mother's
antibodies may cross the placenta and begin destroying the baby's Rh-positive
blood cells while the baby is still in the uterus.  This can lead to anemia,
heart failure, and even stillbirth.

     Can Rh Incompatibility be Prevented?

     About 20 years ago, a substance was developed that could protect a mother
from becoming sensitized to Rh-positive blood.  This substance, called RhO (D)
immune globulin, is injected into the Rh-negative mother shortly after she
delivers an Rh-positive baby, and destroys any Rh-positive blood cells that
may have entered her blood.  After a mother has received this injection, she
will not become sensitized and will not have to worry about Rh complications
developing in her next baby.
     An Rh-negative woman can become sensitized to Rh-positive blood in
situations other than childbirth.  For example, if she has an abortion or a
miscarriage and the fetus was Rh positive, fetal blood may escape into her
bloodstream and she may become sensitized.  Also, after removal of an ectopic
pregnancy (a pregnancy that develops in an abnormal location such as the
fallopian tube), she may become sensitized.  A transfusion of Rh-positive
blood into an Rh-negative woman (which rarely occurs today) may cause
antibodies against Rh-positive blood to form.
     Since it is difficult and sometimes impossible to determine the Rh
factor of the fetus after a miscarriage, abortion, or removal of an ectopic
pregnancy, all Rh-negative women who undergo any of these processes are
automatically given an injection of the immune globulin.
     During your first prenatal office visit, your doctor will perform a blood
test to determine if you have Rh-negative or Rh-positive blood.  If you are Rh
negative, your doctor will also perform another blood test to determine if you
have antibodies that will destroy Rh-positive blood; that test will probably
be repeated during the third trimester of your pregnancy.
     If a pregnant woman does carry antibodies against the Rh factor, an
amniocentesis can be performed to determine if the fetus is being affected.
In the rare instances when serious problems in the fetus are detected, the
baby will be delivered immediately.  If it is determined that the fetus is too
young to survive outside the mother's body, a blood transfusion may be
performed to replace the fetus' Rh-positive blood with Rh-negative blood.


This Month's Visit

During this month's office visit, your doctor will probably:

  -  Check your weight.  By now, you will have gained about 14 to 16 pounds.
  -  Check your blood pressure.  It may be slightly below what it was before
     pregnancy.
  -  Check your urine for sugar and protein.  Normally, You should have
     neither of these in your urine.
  -  Ask about symptoms of pregnancy.  You may now be experiencing heartburn
     and occasional Braxton Hicks contractions.
  -  Ask you how you are feeling.
  -  Ask about the baby's movements.  By now, the baby should be quite
     noticeably active throughout the day.
  -  Check the growth of your uterus with a tape measure.  By now, the top of
     your uterus will be several inches above your navel.
  -  Listen for the baby's heartbeat with a doppler instrument or a
     stethoscope.  The baby's heartbeat should be about 140 to 160 beats per
     minute.
  -  Offer practical advice about the third trimester and describe the
     sensations that you will feel when you are in labor.
  -  Perform no new blood tests.