19 Jun To women with Rh incompatibility (Rh negative or Irregular Antibody positive) during pregnancy
What is Rh incompatibility in pregnancy?
There are many different blood types besides ABO blood type and Rh blood type. The blood type of the fetus is not always the same of the mother’s because its genetic information is inherited from both the fetus’s mother and father.
* ABO blood type: Different blood types between the mother and the fetus cause very few problems.
* Rh blood type: If the mother is Rh-negative and the fetus is Rh-positive, her body will develop anti-D antibody, which attacks fetal blood when it crosses the placental barrier during pregnancy or at delivery. Once the anti-D antibody is produced, the fetal red blood cells will be destroyed and the fetus may develop problems such as severe anemia, fetal edema and severe jaundice (icterus gravis).
* Irregular antibody positive: The fetus may be affected the same way as Rh incompatibility in pregnancy.
* About 0.5% of Japanese women are Rh negative.
* About 2-3% of pregnant women are irregular antibody positive.
Managing Rh incompatibility during pregnancy
* There will be no problem when both the mother and the father of the fetus are Rh negative.
* When the mother is Rh negative, and the father is Rh positive:
The fetus has high chance of being Rh-positive. During pregnancy, the mother will be checked with [indirect Coombs test] every month to find out whether the antibody titer is elevated. If the result of the indirect Coombs test shows that her antibody titer is getting higher, we will consider having exams such as testing amniotic fluid and/or assessing cerebral blood flow in the fetus in order to estimate the effect on the fetus.
If the condition becomes severe, it may be necessary to deliver the baby prematurely or to get a fetal blood transfusion.
Since our hospital does not have NICU (Neonatal Intensive Care Unit), we may transfer the mother-to-be to a facility with NICU if fetal condition is not stable.
Preventive treatment for Rh(−) women
For an Rh(−) woman delivering an Rh(+) baby, human anti-D immunoglobulin should be administered at 28 weeks gestation and after delivery.
If it is administered only once after delivery, the probability of producing anti-D antibody will be 2%. However, if it is administered twice, once during pregnancy and once after delivery, the probability of producing anti-D antibody can be reduced to 0.1%.
The two injections are currently both covered by health insurance. (about 6,000 yen for each when your cost is 30%)
Additionally, since this is a blood derivative, there is a slight risk for infection.
when you do not take preventive measures:
<when no preventive measures are taken> The probability of developing anti-D antibody:
0.7%-1.8% during pregnancy, 8-17% at delivery,
3-6% after miscarriage, 2-5% after diagnostic amniocentesis
<probability that the Rh(+) baby born from Rh(−) mother requires neonatal treatment for anemia or jaundice> 25-30%
<probability that the sensitized mother subsequently gets pregnant with an Rh(+) baby and the baby develops immune fetal hydrops (can be fatal) : 20-25%
Reference: Guideline of Ob-Gyn treatment, section of Obstetrics 2011
(Perinatal Medicine 2009 Vol.39 No.3)
By Kin-ikyo Sapporo Hospital Obstetrics & Gynecology June 2011
translated by SEMI Sapporo September 2013