In order to attempt to determine the cause of a miscarriage, specialists are able to perform an analysis on the chromosomes of the miscarried fetus. Two techniques, karyotype and comparative genomic hybridization (CGH), are currently used to assess the tissue. From the assessment, a doctor can confirm or rule out any unavoidable abnormalities that existed within the fetus to cause the miscarriage.
Karyotype
A karyotype is performed on live cells taken from the miscarried fetal matter. This test generally requires a dilation and curettage (D & C) procedure, following a confirmed miscarriage, in order to collect the best sample. However, some doctors may allow a sterile collection of a naturally expelled miscarriage, since the cells can live after the fetus has died. To perform the karyotype, a specialized lab technician will:
- Collect cells from the miscarried material
- Place the cells in a chemical medium which will allow continued growth
- Chemically suspend division of cells
- Photograph several cells for cross examination
- Arrange and examine the chromosomes for abnormalities
Comparative Genomic Hybridization
The CGH is an upcoming procedure originally used in cancer research. The procedure may be preferable to the karyotype, because collection is not as limited, and controlled studies have shown it more effective in diagnosing abnormalities. Upon the extraction of genetic material, the lab specialist performing the comparative genomic hybridization will:
- Label the DNA
- Dye the DNA
- Hybridize the DNA to an array (allow it to attach to a prepared DNA sample, which is known to be normal)
- Measure the intensity of the resulting dye on the array
Benefits of Analysis
Conducting a chromosomal analysis has great benefits for the woman who has suffered or will suffer multiple losses. At least one study shows that victims of recurrent miscarriage lose a higher number of chromosomally normal babies than the general population (Morikawa et al., 2004). Therefore, if an analysis yields results of a chromosomally normal fetus, it may be indicative of an underlying problem in the mother. Thus, the mother may be more likely to seek testing for potential treatment.
Patient Responsibility
Unfortunately, chromosomal analysis is rarely offered to those who suffer a single miscarriage, since more than 50% of known miscarriages are presumed to be caused by chromosomal abnormality. Most general obstetricians assume chromosomal abnormality is the problem, until a patient has had several miscarriages. Many specialists do offer some type of analysis, but women often will not seek treatment from a specialist until the doctor gives a diagnosis and referral. These women will not know whether any or all of their miscarriages have been caused by unavoidable chromosomal abnormalities, which is information that would be helpful in determining the necessary intervention (if any) required for future pregnancies. Therefore, it is the patient's responsibility to be proactive in seeking an analysis of miscarried material, if it is desired.
Resources for Additional Reading
- Cohen, John. Coming to Term. Houghton Mifflin Co.: 2005
- Lerner, Henry M. , M.D., OB/GYN. Miscarriage: Why it Happens and How Best to Reduce Your Risk . Perseus Publishing: 2003.
- Morikawa et al., “Embryo Loss Pattern is Predominant in Miscarriages with Normal Chromosome Karyotype Among Women with Repeated Miscarriage.” Human Reproduction (vol. 19 no. 11). European Society of Human Reproduction and Embryology: 2004.
Kristen O'Hara - I graduated from college with a B.S. in elementary education. After teaching third grade for two years, I chose to stay home with my ...
