eMedicine Specialties > Obstetrics and Gynecology > General Gynecology
Threatened Abortion
Updated: Sep 30, 2008
Introduction
Background
Threatened abortion is a clinically descriptive term that applies to women who are at less than 20 weeks' gestation with a viable pregnancy and have vaginal spotting or bleeding, a closed cervical os, and, possibly, mild uterine cramping.
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Pathophysiology
Threatened abortions may continue on as healthy term pregnancies or may progress to inevitable, spontaneous, incomplete, or complete abortions.
Threatened abortion
Vaginal spotting or frank bleeding is very common and is experienced in approximately 25% of clinically apparent pregnancies at less than 20 weeks' gestational age. The bleeding and pain that accompany threatened abortion are not usually intense. Threatened abortion rarely manifests with severe vaginal bleeding. Often, the bleeding is temporary and self-limited and possibly due to trophoblastic implantation within the decidualized endometrium.
Approximately half the women with threatened abortions abort, and the remainder continue to have viable pregnancies. Approximately 15% of clinically recognized pregnancies spontaneously abort, and 75% of the losses occur in the first 8 weeks of gestation. The loss rate is estimated to be 2-3 times higher with very early and, often, clinically unrecognized pregnancies. The rate of miscarriage increases with maternal age.
Threatened abortion is defined clinically by the absence of passing/passed tissue and the presence of a closed cervical os. These findings in the setting of a known or presumed viable pregnancy differentiate threatened abortion from later stages of abortion.
Inevitable abortion
Vaginal bleeding is accompanied by dilatation of the cervical canal, no passage of fetal tissue, and, occasionally, gross rupture of the membranes. Bleeding is usually more severe than with threatened abortion and is often associated with abdominal pain or cramping.
Incomplete abortion
Vaginal bleeding is usually heavy and accompanied by abdominal pain. The cervical os is open, with passage of only part of the products of conception. Incomplete abortion is more likely to occur at 6-14 weeks of pregnancy. Some products of conception are still present in the uterus; these typically appear as echogenic material on ultrasonography.
Complete abortion
Patients usually present with a history of bleeding, abdominal pain, and passing of tissue. By the time miscarriage is complete, bleeding and pain have usually subsided and the cervix is closed. Diagnosis may be confirmed by observation of the aborted fetus with the complete placenta. Ultrasonography reveals a vacant uterus with close apposition of relatively thin and regular endometrial interfaces.
Frequency
United States
The World Health Organization estimates that 15% of all clinically recognizable pregnancies end in spontaneous abortion.
Mortality/Morbidity
Surveillance data from 1987-1990 reveal a total of 1459 pregnancy-related deaths in the United States. Spontaneous and induced abortions account for 5.6% of these deaths.
Clinical
History
Any woman of reproductive age with abnormal vaginal bleeding should be considered pregnant until proven otherwise.
- Obtain a careful history, including the following:
- Menstrual history: Deviations from the normal menstrual period may reflect bleeding from implantation of a normal or abnormal pregnancy, which can make accurate dating difficult.
- First date of the last menstrual period (LMP)
- Previous menstrual period
- Usual menstrual interval
- Regularity of menses
- Date of conception, if known
- Medication use since LMP; alcohol, tobacco, and recreational drug use
- Current and past medical problems such as diabetes mellitus, recent infections, bleeding diathesis, thyroid disease, or autoimmune disorders
- Surgical history, particularly operations involving the uterus and adnexa
- Past obstetric history
- Number of term and preterm deliveries
- Number of spontaneous and induced abortions
- Number of living children and major complications associated with deliveries or abortions (eg, blood transfusions, perforated uterus)
- Gynecologic history, including abnormal Papanicolaou test (Pap smear) results, sexually transmitted diseases, and contraception
- Include screening questions regarding sexual abuse or domestic violence.
- Menstrual history: Deviations from the normal menstrual period may reflect bleeding from implantation of a normal or abnormal pregnancy, which can make accurate dating difficult.
- Patients with spontaneous abortion usually present with vaginal bleeding and/or abdominal pain along with a history of passing tissue.
- Vaginal bleeding may vary from slight spotting to significant hemorrhage. Quantifying the amount of bleeding (number of soaked pads or tampons per hour) is very important, as is noting whether the bleeding is improving or worsening.
- Bleeding from threatened abortions frequently is slight, but it may persist for days or weeks.
- The presence of blood clots or tissue may be an important sign of progression of spontaneous abortion.
- Associated pain or cramping should be recorded, including the location, severity, and duration of pain.
- Other symptoms such as fever or chills are more characteristic of a septic abortion.
Physical
Make an immediate assessment of patients who are hemodynamically unstable or experiencing severe vaginal bleeding, including orthostatic vital signs and abdominal and pelvic examination. If orthostatic hypotension is present, initiate intravenous fluid resuscitation and blood cross-match.
- Examine the abdomen, with particular attention to tenderness, bloating, or peritoneal signs suggestive of intraperitoneal hemorrhage.
- Identify the source of bleeding by means of a visual speculum and digital pelvic examination of the cervix. Determine whether the bleeding originates from the vaginal walls, the surface of the cervix, or through the cervical os.
- Determine the intensity of bleeding, examining for the presence of blood clots or tissue fragments.
- Examine for cervical motion tenderness because this finding increases the possibility of ectopic pregnancy.
- Determine the status of the cervical os. If open, it indicates an inevitable or incomplete abortion; if closed, it is a threatened abortion.
- Examine for uterine size, consistency, and tenderness and for the presence of adnexal tenderness or masses. If a mass is suggested, palpation should be gentle because iatrogenic rupture of an ectopic pregnancy or an ovarian cyst is possible.
- If the vaginal or cervical discharge appears abnormal, a wet preparation and cervical cultures (or other testing) for gonorrheal and chlamydial organisms should be performed.
Causes
- Embryonic abnormalities account for approximately 80% of first-trimester abortions.
- Chromosomal abnormalities are the most common cause of spontaneous abortion. Autosomal trisomies account for more than half of the abnormal karyotypes (due to nondisjunction or translocation), and monosomy is the next most common anomaly.
- More than 90% of cytogenic and morphologic errors are eliminated through spontaneous miscarriages.
- Chromosomal abnormalities are found in more than 75% of fetuses aborted in the first trimester.
- The rate of chromosomal abnormalities increases with maternal age. In women younger than 30 years, the rate of miscarriage is approximately 12%; thereafter, the rate increases rapidly, exceeding 50% in women older than 45 years.
- Maternal factors account for the majority of second-trimester abortions.
- Chronic maternal health factors
- Maternal insulin-dependent diabetes mellitus: Up to 30% of pregnancies in patients with poorly controlled diabetes mellitus result in spontaneous abortion.
- Severe hypertension
- Renal disease
- Antiphospholipid syndrome and other thrombophilias
- Systemic lupus erythematosus
- Thyroid disease
- Wilson disease
- Acute maternal health factors
- Infections (eg, cytomegalovirus, rubella, toxoplasmosis, Listeria, Ureaplasma, Mycoplasma, and syphilis)
- Trauma
- Abnormalities of the reproductive system
- Congenital (eg, septate uterus) or acquired defects (eg, uterine synechiae)
- Fibroids
- Cervical incompetence
- Abnormal placental development
- Exogenous factors
- Chronic maternal health factors
More on Threatened Abortion |
 Overview: Threatened Abortion |
| Differential Diagnoses & Workup: Threatened Abortion |
| Treatment & Medication: Threatened Abortion |
| Follow-up: Threatened Abortion |
| References |
| Next Page » |
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Further Reading
Keywords
threatened abortion, threatened miscarriage, miscarriage, incomplete abortion, inevitable abortion, vaginal bleeding, pregnancy complications, early pregnancy loss, pregnancy loss, spontaneous abortion, embryonic abnormality, autosomal trisomy, monosomy, spontaneous miscarriage, chromosomal abnormality, embryonic abnormality, trisomy
