How does abnormal chromosomal disorder lead to early miscarriage?

Dear Doc

Before I found out that I was pregnant I discovered that my blood group was AB negative, which meant that I would have some problems with my pregnancy if the child’s blood group is positive and is mixed with mine. In my ninth week of pregnancy, I had a miscarriage and now I am wondering if there is a possibility that my body has started to produce antibodies.

I do not know what the blood type of the fetus is as it was not tested and my husband’s blood type is positive. This means that my child’s chance of having a negative blood group is 20 per cent. I have no desire to have any children right now because I am still depressed aboutthe miscarriage.

I feel unfortunate to have this type of blood. My gynaecologist did not take time out to find if I have any concerns, she just rushed though the procedure and that hurt even more.

I was told by the nurse at the hospital where I registered, that I should receive some kind of injection to prevent the production of these antibodies.

However, the drawback is the blood products that this injection consists of put me at risk for HIV or hepatitis. I don’t know what to do as I am very confused. I would still like to have a child in the future, but I am scared of the risks that I must take to do so.

What contributes to abnormal chromosomal disorder which usually leads to early miscarriages? I read that if the baby’s heartbeat is in progress, it significantly reduces the chance of miscarriage. If this is so, why did I lose mine?

When I started to spot, could it be that my body started to produce antibodies and attack the fetus?

If my body has become sensitised at, or about 164 levels, how will this affect my ability to have children? Should I do the Indirect Coombs test? What should I do in case I have an unplanned pregnancy?

I miscarried on the 31st January. How soon should I start taking contraceptives? If I resume the pills should I use a condom? If yes, for how long?

Please Doc, I desperately need some answers.

Dear Desperate

All patients have two aspects to their blood group. This includes the AB, O, A, B antigen and the D antigen. Individuals who carry the rhesus D antigen are considered as Rhesus positive and those who do not have the D antigen are considered rhesus negative.

Fifteen per cent of Caucasians are RH negative, while less than 5 per cent of the Jamaican population is rhesus negative. Approximately 17 per cent of Rhesus negative pregnant women married to RH positive males, who do not get Rhoegam, will become sensitised, the majority occurring in patients who have more than one pregnancy.

Rhesus D immune globulin (rhoegam) is prepared from subjects previously sensitised to the Rhesus D Antigen. It absorbs the fetal Rh positive antigen thus blocking the formation of maternal RH antibody at the time of exposure. Therapeutic and spontaneous abortions are associated with a 4 – 5% and a 1.5 – 20 per cent risk of iso-immunisation.

Postpartum of Rhoegam reduces the rate of iso-immunisation. A single dose of Rhoegam should be given within 72 hours and this reduces iso-immunisation by 90 per cent. Routine ante natal administration of Rhoegam to RH negative women at 28 – 29 weeks reduces the rate of iso-immunisation in the third trimester from 2 per cent to 1per cent.

The risk of transmission of viral infections such as human immunodeficiency virus, hepatitis B and C viruses is minimal to absent. All of the blood products used to produce Roegam is tested for viral infections since 1985.

Additionally the process used to prepare the anti D immune globulin removes any viral particles present. If you have already been sensitised you will not benefit from the administration of Rhoegam.

If you have already become sensitised then this could pose a problem in a subsequent pregnancy if the fetus is RH positive. This will result in severe anemia and heart failure in the fetus. Delivery usually has to be undertaken prematurely and there is a problem of severe jaundice in the newborn.

The Indirect Coombs test is useful as this will tell you if you have become sensitised. It is wise to do this test as this will allay a lot of anxiety. If it is negative you have nothing to worry about. If you have an unplanned pregnancy, the Indirect Coombs test should be done early in pregnancy and you will need close monitoring.

It would be wise to register at a facility that has a good special care nursery, such as the University Hospital. This is important in the event that your neonate is RH positive and becomes affected.

Abnormal chromosomal disorders contribute to at least 50% of miscarriages in the early pregnancy (first trimester).

This may occur by chance, may be age related, or may be inherently carried by the mother or the father. The presence of a fetal heartbeat on ultrasound does reduce the chance of a pregnancy loss. However a spontaneous abortion may still occur because of several reasons, the most common in the first trimester being chromosomal abnormalities.

Viral infections and a positive lupus anti coagulant antibody status may contribute. The cause is unknown in the large majority of cases. The resumption of normal menstruation is variable in different individuals after a miscarriage.

So you should start contraceptives as soon s sexual activity is resumed or within 4 weeks of the pregnancy loss. Initially the condom is a very good choice and should be continued even if the pill is used at least of the first month.

The outcome for the vast majority of patients who are RH negative is very good. The risk of sensitization is extremely low with good monitoring and appropriate administration of anti D immune globulin (Rhoegam), so be reassured that you will go on to have perfectly normal pregnancies despite your early pregnancy loss.

Dr Sharmaine Mitchell is an obstetrician and gynaecologist. Email your health queries to Dr Mitchell at mclymonti@jamaicaobserver.com or write to Dear Dr Mitchell, c/o all woman, Jamaica Observer, 40-42 1/2 Beechwood Ave, Kgn 5.