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Spontaneous abortion is noninduced embryonic or fetal death or passage of products of conception before 20 wk gestation. Threatened abortion is vaginal bleeding occurring during this time frame, indicating that spontaneous abortion may occur. Diagnosis is by clinical criteria and ultrasonography. Treatment is usually observation for threatened abortion and, if spontaneous abortion has occurred or appears unavoidable, uterine evacuation.
Fetal death and early delivery are classified as follows:
Abortions may be classified as early or late, spontaneous or induced for therapeutic or elective reasons (see Family Planning: Induced Abortion), threatened or inevitable, incomplete or complete, recurrent (also called recurrent pregnancy loss), missed, or septic (see Table 1: Abnormalities of Pregnancy: Classification of Abortion ).
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Table 1
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| Classification of Abortion |
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Type
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Definition
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Early
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Abortion before 12 wk gestation
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Late
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Abortion between 12 and 20 wk gestation
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Spontaneous
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Noninduced abortion
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Induced
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Termination of pregnancy for medical or elective reasons
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Therapeutic
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Termination of pregnancy because the woman's life or health is endangered or because the fetus is dead or has malformations incompatible with life
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Threatened
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Vaginal bleeding occurring before 20 wk gestation without cervical dilation and indicating that spontaneous abortion may occur
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Inevitable
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Vaginal bleeding or rupture of the membranes accompanied by dilation of the cervix
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Incomplete
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Expulsion of some products of conception
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Complete
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Expulsion of all products of conception
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Recurrent or habitual
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≥ 3 consecutive spontaneous abortions
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Missed
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Undetected death of an embryo or a fetus that is not expelled and that causes no bleeding (also called blighted ovum, anembryonic pregnancy, or intrauterine embryonic demise)
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Septic
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Serious infection of the uterine contents during or shortly before or after an abortion
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About 20 to 30% of women with confirmed pregnancies bleed during the first 20 wk of pregnancy; half of these women spontaneously abort. Thus, incidence of spontaneous abortion is about 10 to 15% in confirmed pregnancies. Incidence in all pregnancies is probably higher because some very early abortions are mistaken for a late menstrual period.
Etiology
Isolated spontaneous abortions may result from certain viruses—most notably cytomegalovirus, herpesvirus, parvovirus, and rubella virus—or from disorders that can cause sporadic abortions or recurrent pregnancy loss (eg, chromosomal or mendelian abnormalities, luteal phase defects). Acquired and hereditary thrombophilias appear to cause abortions after ≥ 10 wk. Immunologic abnormalities and major trauma may be causes. Cause is often unknown.
Risk factors include
Subclinical thyroid disorders, well-controlled or subclinical diabetes mellitus, retroverted uterus, and minor trauma have not been shown to cause spontaneous abortions.
Symptoms and Signs
Symptoms include crampy pelvic pain, bleeding, and eventually expulsion of tissue. Late spontaneous abortion may begin with a gush of fluid when the membranes rupture. Hemorrhage is rarely massive. A dilated cervix indicates that abortion is inevitable.
If products of conception remain in the uterus after spontaneous abortion, vaginal bleeding may occur, usually after a delay of hours to days. Infection may also develop, causing fever, pain, and sometimes sepsis.
Diagnosis
Diagnosis of threatened, inevitable, incomplete, or complete abortion is often possible based on clinical criteria (Table 2: Abnormalities of Pregnancy: Characteristic Symptoms and Signs in Spontaneous Abortions) and a positive urine pregnancy test. However, ultrasonography and quantitative measurement of serum β-hCG are usually done to exclude ectopic pregnancy and to determine whether products of conception remain in the uterus (suggesting that abortion is incomplete rather than complete). However, results may be inconclusive, particularly during early pregnancy.
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Table 2
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| Characteristic Symptoms and Signs in Spontaneous Abortions |
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Type of Abortion
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Vaginal Bleeding
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Cervical Dilation*
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Passage of Products of Conception†
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Threatened
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Y
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N
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N
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Inevitable
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Y
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Y
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N
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Incomplete
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Y
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Y
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Y
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Complete
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Y
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Y or N
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Y
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Missed
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Y or N
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N
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N
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*Internal cervical os is open enough to admit a fingertip during digital examination.
†Products of conception may be visible in the vagina. Tissue examination is sometimes required to differentiate blood clots from tissue products of conception. Before the evaluation, products of conception may have been expelled without the patient recognizing them.
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Missed abortion is suspected if the uterus does not progressively enlarge or if quantitative β-hCG is low for gestational age or does not double within 48 to 72 h. Missed abortion is confirmed if ultrasonography shows any of the following:
For recurrent pregnancy loss, testing to determine the cause of abortion is necessary (see Abnormalities of Pregnancy: Recurrent Pregnancy Loss).
Treatment
For threatened abortion, treatment is observation. No evidence suggests that bed rest decreases risk of subsequent completed abortion. If the cervix is dilated, avoidance of intercourse is often recommended to prevent infection; however, intercourse has not been shown to cause loss.
For inevitable, incomplete, or missed abortions, treatment is uterine evacuation or waiting for spontaneous passage of the products of conception. Evacuation usually involves suction curettage at < 12 wk, dilation and evacuation at 12 to 23 wk, or medical induction (for women without prior uterine surgery) at > 16 to 23 wk (for treatment of late fetal death, see Abnormalities of Pregnancy: Stillbirth). The later the uterus is evacuated, the greater the likelihood of placental bleeding, uterine perforation by long bones of the fetus, and difficulty dilating the cervix. These complications are reduced by preoperative use of osmotic cervical dilators (eg, laminaria), misoprostol, or mifepristone (RU 486).
If complete abortion is suspected, uterine evacuation is done when bleeding occurs or other signs indicate that products of conception may be retained. Uterine evacuation need not be done routinely.
After an induced or spontaneous abortion, parents commonly feel grief and guilt. They are given emotional support and, in the case of spontaneous abortions, reassured that their actions were not the cause. Formal counseling is rarely indicated but should be made available.
Recurrent Pregnancy Loss
(Recurrent or Habitual Abortion)
Recurrent pregnancy loss is ≥ 3 consecutive spontaneous abortions. Determining the cause may require extensive evaluation of both parents. Some causes can be treated.
Etiology
Recurrent pregnancy loss usually results from disorders that cause intrauterine fetal damage, such as maternal or paternal chromosomal abnormalities (eg, balanced translocations). Chromosomal abnormalities may cause 50% of recurrent pregnancy losses, which are more common during early pregnancy; aneuploidy is involved in up to 80% of all spontaneous abortions occurring at < 10 wk gestation but in < 15% of those occurring at 20 wk.
Other common causes may include maternal luteal phase defects (particularly at < 6 wk), overt endocrine disorders (eg, polycystic ovary syndrome, hypothyroidism, hyperthyroidism, poorly controlled diabetes mellitus), severe chronic renal disorders, immunologic abnormalities (eg, lupus anticoagulant, anticardiolipin antibodies, anti-β2 glycoprotein I), and, particularly after 10 wk, inherited maternal thrombotic disorders (eg, activated protein C resistance; factor V Leiden mutation; prothrombin G20210A gene mutation; hyperhomocysteinemia; deficiencies of antithrombin or protein Z, C, or S). Cervical incompetence and structural abnormalities of the uterine cavity (eg, polyps, fibroids, congenital malformations) may predispose to delivery at < 20 wk but do not necessarily cause intrauterine fetal damage.
For women who have a history of recurrent pregnancy loss and who become pregnant, risk of fetal growth restriction and premature delivery may be higher.
Diagnosis
Evaluation should include the following to determine the cause:
Cause cannot be determined in up to 50% of women.
Treatment
Some causes can be treated. If the cause cannot be identified, the chance of a live birth in the next pregnancy is 35 to 85%.
Septic Abortion
Septic abortion is serious uterine infection during or shortly before or after an abortion.
Septic abortions usually result from induced abortions done by untrained practitioners using nonsterile techniques; they are much more common when induced abortion is illegal. Typical causative organisms include Escherichia coli, Enterobacter aerogenes, Proteus vulgaris, hemolytic streptococci, staphylococci, and some anaerobic organisms (eg, Clostridium perfringens).
Symptoms and Signs
Symptoms and signs are similar to those of pelvic inflammatory disease (eg, chills, fever, vaginal discharge, often peritonitis) and often those of threatened or incomplete abortion (eg, vaginal bleeding, cervical dilation, passage of products of conception). Septic shock may result, causing hypothermia, hypotension, oliguria, and respiratory distress. Sepsis due to C. perfringens may result in thrombocytopenia, ecchymoses, and findings of intravascular hemolysis (eg, anuria, anemia, jaundice, hemoglobinuria, hemosiderinuria).
Diagnosis
Septic abortion is usually obvious clinically but must be confirmed by pregnancy testing and usually ultrasonography.
Treatment
Treatment is intensive antibiotic therapy plus uterine evacuation as soon as possible. A typical antibiotic regimen includes clindamycin 900 mg IV q 8 h plus gentamicin 5 mg/kg IV once/day, with or without ampicillin 2 g IV q 4 h. Alternatively, a combination of ampicillin, gentamicin, and metronidazole 500 mg IV q 8 h can be used.
Last full review/revision February 2010 by Antonette T. Dulay, MD
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