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Spontaneous
abortion is noninduced embryonic or fetal death or passage
of products of conception before the 20th wk of pregnancy. Threatened
abortion is vaginal bleeding occurring during this time frame
and indicating that spontaneous abortion may occur. Diagnosis is by
clinical criteria and ultrasonography. Treatment is usually with
bed rest for threatened abortion and, if spontaneous abortion has occurred
or appears unavoidable, uterine evacuation.
Death of the fetus or passage of products of conception (fetus and placenta) before 20 wk of pregnancy is considered abortion. Fetal death after 20 wk is considered late fetal death and, with delivery, is considered a stillbirth. Passage of a live fetus between 20 and 37 wk is considered preterm delivery (see Abnormalities and Complications of Labor and Delivery: Preterm Labor).
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, 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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Abortion that is not induced
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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 to preserve the woman's life or health, or because of fetal death or malformations incompatible with life
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Threatened
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Vaginal bleeding occurring before 20 wk gestation without cervical dilation, which indicates 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 (habitual)
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Two or more consecutive spontaneous abortions
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Missed
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Undetected death of embryo or fetus that is not expelled and causes no bleeding (ie, blighted ovum, anembryonic pregnancy, or fetal 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 1st 20 wk of pregnancy; 1⁄2 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 or recurrent abortions (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. 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. 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 (see
Table 2: Abnormalities of Pregnancy: Characteristic Symptoms and Signs in Spontaneous Abortions) and a positive urine pregnancy test. However, ultrasonography and quantitative measurement of the serum β subunit of human chorionic gonadotropin (β-hCG) are usually done to exclude ectopic pregnancy, to differentiate among the different types of abortion, 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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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.
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†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 it.
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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 disappearance of previously detected embryonic or fetal cardiac activity or absence of such activity > 7 wk in a well-dated intrauterine pregnancy or when the fetal crown-rump length is > 5 mm using transvaginal ultrasonography. Testing to determine the cause of abortion is necessary if women have recurrent abortions (see Abnormalities of Pregnancy: Recurrent Abortion).
Treatment
Treatment of threatened abortion is bed rest, which may minimize bleeding and cramping; however, no evidence indicates that it prevents embryonic or fetal loss. If the cervix is dilated, avoidance of intercourse is often recommended to prevent infection; however, intercourse has not been shown to cause loss.
Treatment of inevitable, incomplete, or missed abortions is uterine evacuation or, at < 10 wk, 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 may be done routinely or only if bleeding or signs of infection develop, suggesting retained products of conception.
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.
Recurrent
Abortion
(Habitual Abortion)
Recurrent
abortion is ≥ 2 consecutive
spontaneous abortions. Determining the cause may require extensive
evaluation of both parents; some causes can be treated.
Etiology
Recurrent abortions usually result from disorders that cause intrauterine fetal damage, such as maternal or paternal chromosomal abnormalities (eg, balanced translocations). Chromosomal abnormalities may cause 50% of recurrent abortions, 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 and prothrombin 20210 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.
Diagnosis
and Treatment
Evaluation may be required to exclude possible genetic causes (see Prenatal Genetic Counseling and Evaluation: Genetic Evaluation). Other tests may include thyroid-stimulating hormone, as well as menstrual history, serum testosterone , fasting plasma glucose and insulin , and ultrasound to rule out polycystic ovary syndrome; BUN and creatinine if chronic renal disorder is suspected; serologic tests for immunologic causes; endometrial biopsies for luteal phase defects; and, if abortions occur after 10 wk, various tests for other thrombotic disorders (see Thrombotic Disorders). Structural uterine abnormalities are evaluated by hysterosalpingography or sonohysterography. Cause cannot be determined in up to 50% of women.
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 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).
Septic abortion is usually obvious clinically but must be confirmed by pregnancy testing and usually ultrasonography. Treatment is intensive antibiotic therapy (eg, clindamycin plus penicillin; ampicillin , gentamicin , plus clindamycin ) plus uterine evacuation as soon as possible.
Last full review/revision November 2005
Content last modified November 2005
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