KEY POINTS
• Spontaneous abortion is the most common complication of early pregnancy.
• Chromosome abnormalities account for a large percentage of all spontaneous abortions.
• Habitual abortion becomes an issue only after three documented (by pathology or ultrasound with heart beat) consecutive spontaneous abortions.
• Septic abortion remains a relatively rare but potentially lethal complication that requires careful management.
BACKGROUND
Definition
• Abortion is the termination of pregnancy by any means, resulting in the expulsion of an immature, nonviable fetus.
• A fetus of 500 g or less that correlates with 20 to 22 weeks’ gestational age (from the 1st day of the last menstrual period), is considered an abortus (1). Note that although “fetus” is the term used in this text for the sake of simplicity, the actual terminology should be “embryo” for any gestation that is 10 weeks or less.
• The term “miscarriage,” although imprecise, has been used for all types of pregnancy losses up to a gestational age of 20 to 22 weeks. Often, its use is preferred in discussions with patients, as the word abortion has undesirable connotations for many people.
• Miscarriage is often classified as either a clinical or a biochemical pregnancy loss. Clinical pregnancies are those that can be identified by ultrasound or histological evidence, while biochemical pregnancies occur earlier and can only be identified by a raised quantitative beta-hCG. In practice, the majority of biochemical pregnancy losses go unnoticed.
Etiology
• Although spontaneous abortion has multiple etiologies, chromosome abnormalities are present in up to 60% of abortuses in some studies (2).
• Abortuses after 12 weeks are less likely to be karyotypically abnormal.
Factors that are known to increase the risk for spontaneous abortion include advanced maternal age, alcohol, cigarette smoking, previous spontaneous abortion, and uterine anomalies.
Epidemiology
• The incidence of spontaneous abortion is believed to be 15% to 20% of all pregnancies. Some have estimated the true incidence to be as high as 50% to 78% (3).
• Fetal loss is higher in women in their late 30s and older irrespective of reproductive history. The risk of a spontaneous abortion by age group: age 20 to 30 years: 9% to 17%; age 30 to 35 years: 20%; age 35 to 40 years: 40%; age 40 to 45 years: 80% (4).
THREATENED ABORTION
Laboratory Tests
• Blood count if bleeding has been heavy.
• Serum β-human chorionic gonadotropin (hCG) level if pregnancy is undocumented or unknown location. Positive tests may occur in nonviable gestations because β-hCG may persist in the serum for several weeks after fetal death (5). Serum levels of β-hCG also help discriminate intrauterine from extrauterine pregnancy.
• In the discriminatory hCG zone concept, the level of hCG is defined above which an intrauterine gestational sac should be identifiable by ultrasound for an intrauterine pregnancy. Failure to identify a gestational sac in the uterus defines the pregnancy as being extrauterine. Ultrasound performed at hCG levels below the zone cutoff will not be expected to demonstrate a gestational sac and therefore, will not be able to distinguish between intra- and extrauterine pregnancies.
• Levels of β-hCG greater than 2500 IU/mL should reflect a greater than 90% chance of intrauterine pregnancy that can be identified by transvaginal ultrasound. Levels greater than 6500 IU/mL should reflect the same capability for transabdominal scans.
• The discriminatory zone is based on a singleton pregnancy. Multiple gestations have proportionately higher hCG levels at any given gestational age. Therefore, the best “discriminatory zone” is a gestation age and not hCG alone (6).
• In pregnancies of 5.5 weeks of gestation or greater (when conception occurs under close observation), transvaginal ultrasonography should identify a viable intrauterine pregnancy with almost 100% accuracy (7,8).
• In a normal pregnancy, the serum β-hCG level should double every 48 to 72 hours. However, in normal pregnancies, the increase may be as low as 50% over the same 48 to 72 hours (9).
• Fetal cardiac activity is normally identifiable by ultrasonography at 6 to 7 weeks of gestation by crown–rump length measurement.
• Absence of fetal heart motion in gestations of 9 weeks or longer predicted nonviable fetuses virtually 100% of the time. Irregular menses and poor or uncertain dates may confuse this evaluation. In such cases, ultrasound should be used to date the pregnancy by crown–rump length (CRL) and use this dating to correlate with the expected rise in β-hCG (serum).
• Other hormone measurements have not generally been helpful in establishing pregnancy viability or location.
• Early pregnancy demise has occurred if there is no cardiac activity with CRL ≥7 mm or a gestational sac of ≥25 mm and no embryo or fetal pole identifiable (10).
Diagnosis
Differential Diagnosis
• Benign and malignant lesions of the genital tract:
• The pregnant cervix often develops an ectropion that is highly vascular, friable, and bleeds easily. Pressure should be applied for several minutes with a large swab to stop any bleeding. If this fails, cautery with silver nitrate sticks is usually successful.
• Atypical or suspicious cervical lesions should be evaluated with colposcopy or biopsy.
• Anovulatory bleeding:
• Patients with irregular menses or amenorrhea may have irregular bleeding that can be confused with threatened abortion. The patient should be questioned about a history of similar episodes of irregular bleeding and cycles greater than 35 days.
• Early symptoms of pregnancy are absent, and the pregnancy test is negative.
• On pelvic exam, the uterus is of normal size and firm; the cervix is firm and not cyanotic.
• Disorders of pregnancy:
• Hydatidiform mole
Patients with a hydatidiform mole usually present with unusually high β-hCG levels and a uterus that is inappropriately large for dates and accentuated by early signs/ symptoms of pregnancy.
The passage of grapelike vesicles from the cervix/vagina arouse suspicion.
The diagnosis is made by ultrasound that shows absence of a fetus (although rarely a fetus and molar pregnancy may occur together) and a white “snow storm” pattern of the hydroptic vesicles.
No heart tones are heard or seen, and severe hyperemesis, early-onset preeclampsia, or hyperthyroidism may be present.
Large ovarian theca lutein cysts may be palpable.
• Ectopic pregnancy
Consider ectopic pregnancy in every patient who has vaginal bleeding and pain in the first trimester. The possibility of ectopic pregnancy is increased if an intrauterine device is in place (11,12).
Ectopic pregnancy is associated with a classical triad of symptoms, usually in both ruptured and unruptured cases: delayed menses, vaginal bleeding, and lower abdominal pain.
Abdominal tenderness or pain is a common sign. It may be unilateral or generalized, with or without rebound, and of such intensity as to preclude an adequate examination.
Light-headedness or syncope (due to hemorrhage and hypovolemia), rectal or urinary pressure, or shoulder pain (due to diaphragmatic irritation) may occur.
Pelvic examination usually reveals cervical motion tenderness and/or a bulging cul-de-sac from the hemoperitoneum. An adnexal mass is palpable 50% of the time.
Ultrasound will usually show an adnexal mass, often containing a gestational sac, an embryo, and even a fetal heart beat. The presence of free fluid in the abdomen may be indicative of a tubal rupture. This would suggest a more urgent clinical situation.
The serum quantitative test will be positive and is most reliable, as the urine pregnancy test may be falsely negative.
Clinical Manifestations
Vaginal bleeding, with or without menstrual-like cramps, in the first 20 weeks of pregnancy is the most common manifestation of threatened abortion. There is frequently no history of passage of tissue or rupture of membranes.
• Symptoms of pregnancy are often decreased in intensity.
• Physical exam is normal, except that the speculum exam may reveal a small amount of bleeding with a closed cervix and no more than mild discomfort.
Treatment
• Traditional treatment is bed rest and abstinence from intercourse; however, controlled studies supporting the efficacy of bed rest are lacking (13).
• Symptoms are best managed on an outpatient basis with hospital admission reserved for heavy bleeding and/or pain relief.
Medications
• There is no evidence that any hormones or medications alter or improve the outcome of threatened abortion in the first and early second trimester.
• Medications given during the period of organogenesis (days 18 to 55 after conception) may have teratogenic effects on the fetus. This may need to be balanced with the health of the mother.
• A regimen of bed rest and abstinence from sexual intercourse seems more rational for late threatened abortions (after 12 weeks of gestation), although the efficacy of such has not been confirmed.
Patient Education
• Patients can be reassured that bleeding during early pregnancy is very common and that the prognosis for a normal child in those who do not abort is excellent. However, some studies have reported that bleeding early in pregnancy is associated with an increase in abruptio placentae, placenta previa, prematurity and its complications, and a slight increase in anomalies, although perinatal mortality is not affected.
• If there is no cramping, the chances are 50% to 75% that the pregnancy will continue successfully. If the pregnancy is 7 to 11 weeks’ gestational age and ultrasound has noted no fetal heart beat, there is a 90% to 96% chance the pregnancy will not continue (14).
• The patient should be told to report increased bleeding (greater than a normal menses), cramping, passage of tissue, or fever.
• Tissue passed should be saved for examination.
INEVITABLE ABORTION
Diagnosis
Clinical Manifestations
• The symptoms of threatened abortion are present, and the internal cervical os is dilated as seen on ultrasound exam.
• The patient usually complains of menstrual-like cramps or pelvic pressure.
Differential Diagnosis
• Threatened abortion:
• The internal cervical os is closed on ultrasound exam.
• The cervix should not be examined with instruments, as bleeding may also occur with a normal pregnancy.
• Incomplete abortion:
• The cervix is dilated and either
Some tissue has already has passed (by history) or
Tissue is present in the vagina or the endocervical canal
• Complete abortion:
• Positive pregnancy test with a history of
Abortion symptoms
Passage of tissue via vagina
• No evidence of tissue or gestational sac in the uterus on ultrasound
• Ectopic pregnancy is a possibility if no tissue is present.
• Incompetent cervix:
• Cervical dilation without pain or contractions that occur only in the second trimester after 15 weeks of gestation.
• Transvaginal ultrasound of the cervix may show “funneling” of the internal os or shortening (less than 2.5 cm) of the cervical length.
Treatment
Medications
• Rho (D) immunoglobulin (RHoGAM) is administered if the patient is Rh negative.
PROCEDURES
• Surgical evacuation of the uterus is advised in nearly all cases because
• Progression to complete abortion will occur in a few hours to days
• Placental tissue is likely to be retained in gestations of 10 to 14 weeks.
INCOMPLETE ABORTION
Laboratory Tests
• Complete blood count.
• Rh typing.
• Consider blood type and cross-match if bleeding is heavy or if vital sign postural changes are present.
• Consider karyotyping products of conception (POC) if there is a history of recurrent losses.
Diagnosis
Differential Diagnosis
Differential diagnosis is the same as that for inevitable abortion.
Clinical Manifestations
• Along with cramping and bleeding, the patient may report the passage of tissue. Caution should be taken not to mistake organized clots for tissue.
• Speculum examination reveals a dilated internal os with tissue present in the vagina or endocervical canal.
Treatment
Medications
• RHoGAM is administered to Rh-negative, unsensitized patients.
PROCEDURES
• Stabilization
• If the patient has signs and symptoms of heavy bleeding, at least one large-bore intravenous catheter suitable for blood transfusion (16 gauge or larger) is started immediately, if she has unstable vital signs.
• Ringer lactate or normal saline with 30 U oxytocin per 1000 mL is started at 200 mL/h and increased if necessary to obtain uterine tone (the uterus is less sensitive to oxytocin in early pregnancy). Such doses may depress urine output because of the antidiuretic hormone–like activity of oxytocin and should be discontinued as soon as appropriate.
• POC should be removed from the endocervical canal and uterus with ring forceps or suction. This maneuver often dramatically decreases the bleeding.
• Curettage
• The patient is placed in a dorsal lithotomy position in stirrups and suitably prepared, draped (as for vaginal delivery), and sedated.
• Conscious sedation may be used.
• Bimanual examination confirms the position and size of the uterus and the direction of the endocervical canal.
• The cervix is exposed, and the vagina and cervix are cleaned with povidone–iodine solution or Hibiclens if the patient has an allergy to iodine.
• Paracervical block may be performed with chloroprocaine hydrochloride 1% (Nesacaine) or another agent, 12 mL total, divided into equal doses and injected submucosally into the lateral vaginal fornices, with a 20-gauge spinal needle at 2, 4, 8, and 10 o’clock (3 mL each site).
• Beware of inadvertent intravenous injection. It this occurs, the patient may note tinnitus or a metallic taste in her mouth. Stop and allow symptoms to resolve.
• Amount of dilation (in millimeters) of cervix required for a given gestation is equal to the gestational age in weeks (e.g., dilate to no. 9 Hegar for a 9-week pregnancy).
• Curettage is performed carefully but systematically with a suction instrument. A single-tooth tenaculum or a ring forceps placed on the anterior cervical lip is used for countertraction. Vacuum curettage may be faster and result in less blood loss with advanced gestations. Use of a vacuum curette that is 1 mm smaller than the measured cervical dilation is recommended. To decrease perforation risk, advance the tip of the curette no farther than the middle of the uterine cavity. Ultrasound guidance may be helpful. Sharp curettage and then exploration with polyp or ring forceps should follow vacuum aspiration to ensure completeness.
• Perforation
• Great care must be used, especially in gestations exceeding 12 to 14 weeks, to avoid perforation of the uterus.
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