Spontaneous Abortions Causes

The abortion is termination of pregnancy for any reason before the fetus is developed enough to survive. There are various definitions, with slight variations, one is the termination of pregnancy before 20 weeks from the first day of the last normal menstrual period. Another is the removal of a product (or an unborn fetus) that weighs less than 500 grams.

Spontaneous abortion is defined as the involuntary loss of pregnancy before the fetus is viable, ie before 22 weeks gestation.It is called early abortion that occurs before eight weeks gestation, 80% of spontaneous abortions occur in this phase. The rest usually happens between weeks 13 and 14 of gestation, and are called late-term abortions.
Most early abortions up to aberrant or anembryonic eggs (no embryo), while those with fetal abortions are usually late.

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The causes of spontaneous abortion are many, among which are occurring more often may include:
Fetal factors
The most common situation in early spontaneous abortion is a malformation in the development of the zygote, embryo, early fetus, or sometimes the placenta. Genetic causes are most common in this type of abortions: they produce eggs aberrant result of alterations in meiosis (cell division in which daughter cells have half the chromosomes of the mother cell). In these cases, parents have normal karyotypes but are frequent anomalies: trisomy autonomic (anomaly characterized by the appearance of a superfluous chromosome in the pair determines sex), triploidy (abnormality in the triple chromosomal displayed instead of double), monosomy X (anomaly characterized by the loss of a chromosome), tetraploidy (genetic mutation in which the chromosomal endowment is double with respect to the parent) and alterations in the rearrangement of chromosomes. These anomalies were found in 80% of aberrant eggs and between 5 and 10% of those abortions where the fetus is.
In chromosome analysis has been observed up to 60% of malformations,common in embryos and fetuses  are responsible for the majority of early abortions. Jacob and Hassold (1980) reported that about 25% of chromosomal abnormalities are occur due to errors in the process of gamete formation (gametogenesis mother) and 5% to paternal errors.
Maternal factors
Some of the maternal factors that often influence the development of the product are incorrect infections. For example, herpes simplex, is associated with an increased incidence of genital infections after abortions in early pregnancy. Other conditions also associated with maternal antibodies are human immunodeficiency virus type 1 (HIV-1), syphilis and the presence of group B streptococcus in the vagina and infection by Mycoplasma hominis and Ureaplasma urealyticum. Pre-pregnancy treatments have been shown to prevent recurrent spontaneous abortion.

Sometimes, recurrent spontaneous abortions are due to autoimmune reactions (immunity against self) and alloimmune (immunity against another person). Also respond to endocrine-logical. There is some controversy about whether diabetes mellitus is a cause of spontaneous abortion, however, several studies have found that women with high levels of glucose and glycated hemoglobin are at higher risk of abortion than retaining good metabolic control. Although in these cases the frequency of congenital malformations is higher, no losses were observed early.

Progesterone deficiency or lutein (a hormone produced in the ovaries during the second part of the menstrual cycle and pregnancy) as a cause of abortion is not fully proven. However, its effect on uterine contractions and the absence of malformations, progesterone is usually given in cases of threatened early abortion in pregnant patients with uterine fibroids, or those to which they have applied a cervical cerclage ( temporary suture to keep the cervix closed).
Another cause is polycystic ovarian syndrome, high number of cystic formations, often the result of unfertilized eggs that were not eliminated during menstrual bleeding. Anatomical abnormalities of the uterus cause 10 to 15% of all abortions in proper fetal development. Incompetent cervix (which opens prematurely under the pressure of the uterus and fetus, for various reasons) is a recognized cause of pregnancy loss at the beginning or end of the second quarter. This disorder is diagnosed by a history of pregnancy loss with late abortions, painless, with bulging or rupture of membranes, usually with a live fetus and increasingly low gestational age.

Antifosfolípi antibody syndrome-do is another cause of spontaneous abortion. There are various antiphospholipid antibodies, the most important are the lupus anticoagulant, anticardiolipin antibody and antibody causing false positive test for syphilis. The presence of one or more of three antiphospholipid antibodies associated with recurrent pregnancy loss I, arterial or venous thrombosis, preeclampsia (significant increase in blood pressure) or severe early intrauterine growth retardation and chorea gravidarum (A syndrome characterized by unusual jerky movements of the fetus). Most miscarriages happen because of this between 14 and 18 weeks of gestation and up to 28% of patients with thrombosis.

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