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At least 60% of spontaneous miscarriages occur because of a chromosomal abnormality at conception. This means that a genetically (chromosomally) defective sperm or ovum gives rise to a genetically abnormal fetus. The miscarriage is Nature's defense mechanism, which aborts a defective fetus, rather than giving birth to a defective baby. Since most of these genetic defects are chance occurrences, the risk of the defects being repeated again in the next pregnancy is very small.
In order to establish the diagnosis of a genetic cause for repeated pregnancy loss, a karyotye (study of the chromosomes) of the fetal tissue (if available) may be done. A Karyotype is expensive, and often the fetal cells fail to grow in culture, so that the study may not be possible. Moreover, since little can be done even if a defect is detected, it has little impact on patient management. However, it does provide an explanation for some patients with recurrent pregnancy loss.
In about 5% of couples, a chromosome abnormality found in one of the partners explains recurrent miscarriage. This abnormality is detected by doing a chromosomal study on the parent's blood. The commonest problem is a structural defect (break or loss of a piece of the chromosome; or a rearrangement of a bit of a chromosome).
If the karyotype is normal, then the patients can be reassured that the miscarriages were a chance genetic event, and they can feel comfortable continuing with their efforts to have a baby. However, if the karyotypes are abnormal, this is a permanent situation, which indicates an increased risk of miscarriage. Genetic counselling should be sought to discuss the degree of risk. Depending upon the individual problem, this risk may be anywhere from 25% to 100%. Since chromosomal rearrangement at conception (when the sperm fertilises the egg) is a random event, there is little which can be done to treat this. Options may include: continuing to try to conceive a baby naturally; adoption; donor eggs (if the wife is suffering from the genetic problem) or donor sperm (if the husband is affected by the genetic problem). Very recently, preimplantation genetic diagnosis has also been used in order to select and transfer only the genetically normal embryos after performing IVF. However, this is expensive treatment, which is available at very few clinics so far, and can only be used when the genetic error in the parents has been accurately diagnosed.
© Dr. Aniruddha Malpani and Dr. Anjali Malpani www.drmalpani.com
Credits: How to Have a Baby: Overcoming Infertility
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