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rmality. Indeed, 25-35% of stillborn infants undergoing autopsy have intrinsic abnormalities (Wapner et al., 2002) .These include single malformations (40%), multiple malformations (40%), and deformations or dysplasia (20%) (Wapner et al., 2002). Almost 25% ofstillborns due to intrinsic defects show an abnormal karyotype whereas the rest of the 75% may have genetic defects which are not identifiable by the regular cytogenetic tests. This holds good for fetuses with multiple abnormalities.

Single gene mutations may be responsible for death of the fetus in early weeks of development. Stillbirths in the midgestational weeks might be due to abnormal placental growth, development, or angiogenesis. Some autosomal recessive disorders including glycogen storage diseases and hemoglobinopathies have been reported as the cause of stillbirth (Wapner et al., 2002). In male fetuses, X-linked disorders may prove to be fatal. Many other genetic defects that are not recognized by the conventional cytogenetic diagnostics may lead to stillbirth.

For example, conventional karyotype cannot identify chromosomal microdeletions that are linked with unexplained mental retardation. Confined placental mosaicism has also been associated with fetal growth impairment and stillbirth (Kalousek et al., 1994). Heritable Thrombophilia is another probable etiology of stillbirth.It is thought that placental infarction occurs due to thrombosis in the uteroplacental circulation leading to death. This poses concern over other thrombophilic defects and their effects on stillbirth.

It is noteworthy that many heritable thrombophilias are common in normal individuals without a history of thrombosis or pregnancy loss (Rey et al., 2003). Even though many studies relate thrombophilias to fetal loss, most of the women with thrombophilias have healthy pregnancies with no lethal complications. It can be said that in the absence of any previous obstetric problems, thrombophilia will not result in stillbirth.

Feto-maternal Hemorrhage:

Feto-maternal hemorrhage has been linked to almost 3- 14% of all stillbirths which implies that it is responsible for a considerable number of stillbirths. Obstetric procedures such as external cephalic version and cesarean section lead to fetal maternal hemorrhage. Hemorrhage can also result due to placental abruption and/or abdominal trauma during pregnancy. Fetal maternal hemorrhage must be identified and quantitated using a proper dependable diagnostic test to attribute this reason behind the death of fetus. Hypoxia and anemia are indicators of death due to fetal hemorrhage. So, they should be confirmed by autopsy as in some normal cases too, few fetal cells can be seen in maternal blood.

Maternal Features:

Delayed child bearing or increased maternal age, prepregnancy obesity and stress are found to have their effects on the occurrence of stillbirth. The underlying mechanisms of action are unknown; however, with both obesity and delayed child-bearing on the rise, their importance as potential causes of stillbirth deserves greater attention (Cnattingius et al., 2002). Women whose only risk factor is being overweight have about a 2-fold increased risk of s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。