Spontaneous abortion

Spontaneous abortion. It is defined as the expulsion of the embryo or fetus before it is viable (500 g or less or before 20-22 weeks of gestation). The incidence varies depending on whether or not preclinical embryo losses are taken into account (prior to clinical demonstration of pregnancy ). Studies to demonstrate these early pregnancies by determining human chorionic gonadotropin ( HCG ) have reported preclinical losses of 8-57%.


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  • 1 Etiology
  • 2 Diagnosis
  • 3 Treatment
  • 4 Sources


Among the possible causes of EC (spontaneous abortion), the most common is a genetic abnormality of the embryo . Most of these abnormalities appear to be autosomal chromosomal trisomies . The frequency of chromosomal abnormalities in late abortions is much lower. Anatomical defects due to polygenic / multifactorial or Mendelian factors appear to be responsible for a relatively higher proportion of late fetal losses. Risk factors for EC are advanced maternal age, maternal illnesses, smokingand the consumption of alcohol and other substances. Women ages 40-44 are twice as likely to have fetal loss as women ages 20-30, for both genetically normal and abnormal fetuses. The explanations for this phenomenon are the accumulated exposure to toxins, the greater probability of acquiring an infection, a lower response of the luteal phase and a poorly vascularized endometrium .

The maternal diseases associated with AE are autoimmune, especially Systemic Lupus Erythematosus (SLE), hemoglobinopathies , poorly controlled insulin-dependent diabetes mellitus, and HIV infection ; however, any serious maternal illness can increase the risk of EC. Finally, EC has also been associated with jobs that expose women to anesthetic gases, lead, and ethylene oxide, along with some drugs, such as warfarin, anticonvulsants such as trimethadione , phenytoin, and valproic acid, and antineoplastic drugs . It has been observed that women over 30 years old who takeOral contraceptives for more than 8 years show a significant decrease in the rate of EC. To explain this, it has been proposed that long-term use of oral contraceptives conserves follicle number and protects against EC due to aneuploidy. In women with AER, numerous factors have been identified as possible causes. It appears that parental chromosomal abnormalities, such as balanced translocations, account for only 4-5%.

Uterine abnormalities are involved in an additional 5-30%, although this depends on the definition used. Karyotype analyzes of recurrent abortion specimens show a specific chromosomal abnormality in up to 70% of cases. the AntibodiesAntiphospholipids (lupus anticoagulant and anticardiolipin) are often associated with AERs in women with SLE or other autoimmune diseases, but are also found in 7-8% of women without them. Prospective studies show that the frequency of abortions in patients with a syndrome associated with the presence of antiphospholipid antibodies is close to 60%. Other proposed mechanisms are immunological causes, such as the failure to manufacture blocking antibodies against fetal antigens, and vasospastic disorders.


Threatened abortion (vaginal bleeding during the first half of pregnancy) occurs in 20-25% of pregnancies, and half of these women abort. The evaluation is carried out by means of a hematocrit and the search for the origin of the hemorrhage and for any evidence of dilation of the cervix or expulsion of products of conception. The ability to differentiate a viable fetus from another that is not viable depends on gestational age and available means.

The ultrasound transvaginal can see the gestational sac at 4 weeks, the yolk sac at 5 and fetal cardiac activity at 6 weeks of gestation, about one week before each of these parameters can be seen on transabdominal ultrasound. Demonstration of fetal life during weeks 6 to 9 is associated with a viable fetus in 90-100% of cases. Combining the ultrasound evaluation with hormone levels can improve the ability to predict the prognosis of pregnancy. Accuracy rates of up to 100% have been reported for the prediction of AE when demonstrating no fetal life at 6 weeks gestation with low estradiol levels, or when demonstrating low levels of HCG and estradiol also at 6 weeks.

In cases of threatened abortion, a single determination of a Progesterone level lower than 45 nmol / l could also differentiate AE and ectopic pregnancies from viable pregnancies (sensitivity, 87.6%; specificity, 87.5% ). Serial HCG determinations that do not show increases in levels for several days are a poor prognostic sign. On the other hand, when the values ​​of HCG, pregnancy-specific b1-glycoprotein and estriol, as well as ultrasound, are normal between 6 and 9 weeks of gestation, the prognostic precision of viability is also close to the 100.


If the bleeding is mild, the standard acute treatment of threatened abortion is expectant. Many physicians recommend restriction of activity and abstinence from intercourse for several days to a week after the bleeding stops . However, there is no evidence to support these recommendations. If the ultrasoundshows signs of fetal life, especially if they are associated with laboratory tests, the woman or the couple can be reassured and told that the prognosis is good. The finding of intrauterine or subchorionic hematomas on ultrasound does not appear to adversely affect pregnancy. In cases of incomplete abortion with partial expulsion of the products of conception, the uterine contents are usually evacuated. Unless there is excessive bleeding, pain or psychological distress, curettage is usually not necessary in cases of unavoidable abortion (symptoms of threatened abortion accompanied by dilation of the cervix and obvious rupture of the membranes ) or threatened abortion with signs of poor prognosis.

In a descriptive study of EA carried out by researchers from the Ambulatory Sentinel Practice Network (ASPN), the curettage that was performed (in 51% of the cases) was done mainly due to persistent pain, tissue retention and excessive bleeding; complications observed during follow-up were similar in the group of women who underwent curettage and in the group who did not. Most cases of unsuccessful abortion (withholding of abortion at least 4 weeks after fetal death) are caused by EC. In cases where this is not the case, the methods to induce uterine evacuation are curettage during the first 14 weeks of gestation or, if the pregnancy is more advanced, stimulation of uterine contractions with oxytocin orprostaglandins .

Although effective in inducing abortion, vaginal administration of a prostaglandin E1 (PGE1) analog to terminate a failed abortion causes complete abortions in only about 50% of cases. The products of conception should be examined to ensure complete expulsion, and a curettage should be performed if the entire fetus and placenta cannot be identified . After EC, Rh negative women should receive Rh0 (D) immune globulin to prevent sensitization. The need to use Rh0 (D) in threatened abortion is not yet clear.. Treatment of women with AER begins with an evaluation of the possible causes and is related to those that are identified, such as antibiotics if infection exists or surgical correction of uterine abnormalities.

For the prevention of EA in women with antiphospholipid antibodies, promising results have been obtained using low-dose acetylsalicylic acid (60-80 mg / day) and prednisone (40-60 mg / day) or low-dose acetylsalicylic acid and heparin (5,000-10,000 U, twice a day). Because of the possible side effects of these treatments, treatment with only low-dose acetylsalicylic acid deserves well-studied. Immunization to produce blocking antibodies has also been suggested. Although immunization with parental leukocytes has been used , trophoblastic vesiclesor donor seminal plasma, to date the efficacy of this treatment is uncertain. Perhaps the most important aspect of treatment is a supportive and caring attitude on the part of the medical and nursing staff.

If the tests are normal, the woman should be reassured and supported, because even after three consecutive ECs, the chances of a successful pregnancy are 75% at best and 54% at worst, in compared to the 86% expected overall. In a study of women with unexplained AER, treated with a formal emotional support program and strict supervision, a success rate of 86% was achieved in subsequent pregnancy.


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