Genetic test of the aborted fetus or death neonatal

Spontaneous abortion is one of the most common problems during pregnancy and according to the studies conducted, 10% to 15% of pregnancies lead to abortion and a smaller number are lost in the womb after 20 weeks of pregnancy. All these cases require histopathological and genetic investigations so that, based on the diagnosis of the cause of abortion, it can be done to prevent its recurrence in subsequent pregnancies. In addition, since 50% of spontaneous abortions are caused by chromosomal abnormalities, the diagnosis of the type of chromosomal abnormality determines the probability of recurrence in the next pregnancy. In some cases, such as chromosomal aneuploidy, the risk of recurrence is low, and in cases such as chromosomal translocations, the risk of recurrence is very high. Therefore, identifying the type of fetal abnormality plays a decisive role in estimating the risk of recurrence as well as suggesting prenatal diagnostic methods in subsequent pregnancies.

The presence of cases such as a history of repeated abortions, infertility, involvement of various organs of the fetus (numerous fetal anomalies), the presence of mentally retarded people in the family, etc. suggest the possibility of chromosomal disorders. In such cases, genetic tests on the sample of the aborted fetus can be helpful.

 Genetic tests that can be performed on the fetus include the following:

• Diagnosis of a number of common chromosomal disorders (monosomy - trisomy) including chromosomes 13, 18, 21, X and Y
• Diagnosis of chromosomal disorders of a number (monosomy-trisomy) of other chromosomes
• Detection of subtelomeric rearrangements of all chromosomes (deletions and additions of the terminal regions of chromosomes are known causes of numerous fetal anomalies.)
• Diagnosis of syndromes of microchromosomal deletions (with new molecular cytogenetic techniques, it is possible to

simultaneously check the fetal sample for the following syndromes in one test session). These syndromes include:

• Cri du Chat syndrome, 5p15
• DiGeorge region 2, 10p15
• DiGeorge syndrome 22q11
• Langer-Giedion syndrome, 8q
• MECP2/Xq28 duplication
• Miller-Dieker syndrome, 17p
• NF1 microdeletion syndrome
• Prader-Willi / Angelman
• Rubinstein-Taybi syndrome
• Smith-Magenis syndrome
• Sotos syndrome 5q35.3
• WAGR syndrome
• Williams syndrome
• Wolf-Hirschhorn 4p16.3
• 1p36 deletion syndrome
• 2p16 microdeletion
• 3q29 microdeletion
• 9q22.3 microdeletion
• 15q24 deletion syndrome
• 17q21 microdeletion
• 22q13 / Phelan-McDermid

Until the introduction of new molecular cytogenetic techniques, karyotyping was the only tool for investigating chromosomal disorders. Since this technique is based on cell culture, it requires a sterile and fresh sample. Normally, the samples of aborted fetuses do not meet the mentioned conditions due to contamination and the time required for the sample to reach the laboratory. As a result, in most cases, the culture of embryo samples is not successful. In addition, due to the limitation of accuracy of this method (about 2 to 5 million bp), deletions and small duplications cannot be detected by this technique.

By using these methods, the required DNA can be extracted from any type of fetal tissue that has been delivered to the laboratory in frozen form. On the other hand, the sterility of these samples is not a necessary condition for performing these tests. In this way, there will be no past restrictions for sending samples. In addition, new molecular cytogenetic techniques are more accurate than classical methods and have the ability to detect microchromosomal deletions and duplications that cannot be detected by conventional methods (karyotype).

The best conditions for sending a sample for genetic testing should be fresh or frozen tissue without being placed in alcohol, formalin or other fixative solutions in a syringe or microtube and delivered to the laboratory.