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illbirth might be attributed to it. Toxoplasma gondii, leptospirosis, Listeria monocytogenes, Q fever, and Lyme disease are associated with the occurrence of stillbirth (Goldenberg et al., 2003). The magnitude of stillbirths due to viral infections is not known mainly due to the absence of a well defined systematic evaluation of infections in stillborn infants. The problem lies behind the fact that these viruses are difficult to culture and moreover, a positive viral serological diagnostic test identifying the DNA or RNA of the virus in the fetal tissue or placental tissue does not definitely determine that infection was the reason behind death. In most of the cases, infection is linked with stillbirth in early gestational weeks around twenty weeks. If molecular diagnostic technology (DNA and RNA polymerase chain reaction [PCR]) is utilized, it will help in diagnosis of viral infections without any error.

Parvovirus B-19 appears to have the strongest association with stillbirth. According to a Swedish survey, in 8%of stillbirths B-19 PCR positive tissues were observed (Enders et al., 2004). In the United States, less than 1% of all stillbirths are reported to be due to parvovirus infection Parvovirus B19 moves across the placenta spreading the infection to fetal erythropoetic tissue resulting in fetal anemia leading to fetal death (Wapner et al., 2002). Myocardial damage may also occur due to Parvovirus B19.

Here the virus directly attacks the fetal cardiac tissue. Parvovirus infection that leads to stillbirth usually occurs before 20 weeks of gestation (Wapner et al., 2002). Enteroviruses which include Coxsackie A and B, echoviruses and other enteroviruses are associated with stillbirth. Coxsackie viruses can cross the placenta and lead to villous necrosis, inflammatory cell infiltration, calcific pancarditis, and hydrops. Echovirus infection begins with severe maternal illness and finally ends with stillbirth. Cytomegalovirus (CMV) belongs to herpesvirus family and it is a congenital viral infection. Initially, the mother is infected and then it is transmitted to the fetus. CMV causes placental damage leading to intrauterine fetal growth restriction, but an association with stillbirth remains controversial (Goldenberg et al., 2003). Viral infections in the mother like rubella, mumps and measles are linked with stillbirth. If the vaccinations are administered on time then the proportion of stillbirths occurring due to infections can be reduced greatly.

Genetics:

Genetic causes are responsible for a considerable magnitude of stillbirths. 6- 12% of stillbirths attributed to genetic etiologies are due to karyotyping abnormalities. Due to the fact that in some of the cases cells cannot be cultured, karyotyping is not possible. Such factors alter the exact estimate of stillbirths resulting from chromosomal abnormalities. In stillborn fetuses which show apparent structural defects the probability of chromosomal abnormality is much higher when compared to normal stillborn fetuses.

The usually focused abnormalities include monosomy X (23%), trisomy 21 (23%), trisomy 18 (21%), and trisomy 13 (8%). There are many instances where the karyotype of the stillborn is normal yet the cause of death is a genetic abno本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。