By convention, the definition of abortion is the termination of pregnancy, either spontaneously or intentionally, before 20 weeks based upon the date of the first day of the last normal menses. Another commonly used definition is the delivery of a fetus–neonate that weighs less than 500 g. Definitions vary, however, according to state laws for reporting abortions, fetal death, and neonatal deaths.
More than 80 percent of abortions occur in the first 12 weeks. Chromosomal anomalies cause at least half of these early abortions. The risk of spontaneous abortion increases with parity as well as with maternal and paternal age. Clinically recognized spontaneous abortion increases from 12 percent in women younger than 20 years of age to 26 percent in women older than 40 years. Finally, the incidence of abortion is increased if a woman conceives within 3 months of a term birth.
IMPACT ON FUTURE PREGNANCIES
Fertility is not altered by an abortion. A possible exception is the small risk from pelvic infection. Vacuum aspiration results in no increased incidence of midtrimester spontaneous abortions, preterm deliveries, or low-birth-weight infants in subsequent pregnancies. Multiple sharp curettage abortion procedures, however, may result in an increased risk of placenta previa.
Serious complications of abortion have most often been associated with criminal abortion. Severe hemorrhage, sepsis, bacterial shock, and acute renal failure have all developed in association with legal abortion but at a very much lower frequency. Metritis is the usual outcome, but parametritis, peritonitis, endocarditis, and septicemia may all occur. Two-thirds of septic abortions are due to anaerobic bacteria. Coliforms are also common. Other organisms reported as causative of septic abortion include Haemophilus influenzae, Campylobacter jejuni, and group A streptococcus. Treatment of infection includes prompt evacuation of the products of conception along with broad-spectrum antimicrobials given intravenously. If sepsis and shock supervenes, then supportive care is essential as discussed in Chapter 43. Septic abortion has also been associated with disseminated intravascular coagulopathy.
Resumption of Ovulation
Ovulation may resume as early as 2 weeks after an abortion. Therefore, if pregnancy is to be prevented, it is important that effective contraception be initiated soon after abortion.
It is convenient to consider the clinical aspects of abortion under seven subgroups: threatened, inevitable, incomplete, missed, recurrent, therapeutic, and elective. The first five subgroups are spontaneous abortions.
Legally induced abortion (therapeutic or elective) is a relatively safe procedure, especially when performed during the first 2 months of pregnancy. The risk of death from abortion performed during the first 2 months is about 0.7 per 100,000 procedures. The relative risk of dying as the consequence of abortion is approximately doubled for each 2 weeks of delay after 8 weeks’ gestation.
The clinical diagnosis of threatened abortion is presumed when any bloody vaginal discharge or bleeding appears during the first half of pregnancy. Bleeding usually begins first, and cramping abdominal pain follows a few hours to several days later. Threatened abortion is extremely commonplace, with one out of four or five women experiencing vaginal spotting or heavier bleeding during early pregnancy. Approximately half of these women will abort. Those women who do not abort are at an increased risk of suboptimal pregnancy outcomes such as preterm delivery, low birth weight, and perinatal death. The risk of a malformed infant does not appear to be increased.
The differential diagnosis in women with such bleeding should include physiological bleeding at the time of menses, cervical lesions, cervical polyps, cervicitis, and decidual reaction in the cervix. Lower abdominal pain and persistent low backache do not usually accompany bleeding from these benign causes. Importantly, ectopic pregnancy should always be considered in the differential diagnosis of threatened abortion.
Each woman should be examined carefully for the possibility that the cervix already is dilated, in which case abortion is inevitable (see later discussion), or there is a serious complication such as ectopic pregnancy or torsion of an unsuspected ovarian cyst. Treatment of threatened abortion may include bed rest at home with analgesia given to help relieve the pain. If bleeding becomes serious or persists, the woman should be reexamined and the hematocrit checked. If blood loss is sufficient to cause anemia or hypovolemia, evacuation of the pregnancy is generally indicated.
Occasionally, slight bleeding may persist for weeks. Vaginal sonography, serial serum quantitative chorionic gonadotropin (hCG) levels (Appendix B, “Ultrasound Reference Tables”), and serum progesterone values, measured alone or in various combinations, have proven helpful in ascertaining if a live intrauterine pregnancy is present.
Women who are D negative with a threatened abortion probably should receive anti-D immunoglobulin, because more than 10 percent of such women have significant fetomaternal hemorrhage.
Inevitable abortion is often signaled by gross rupture of the membranes in the presence of cervical dilatation. Under these conditions, abortion is almost certain. Uterine contractions usually begin promptly or else infection may develop.
With obvious membrane rupture or significant cervical dilatation, the possibility of salvaging the pregnancy is very unlikely. If there is no pain or bleeding, the woman may be placed on bed rest and observed for further leakage of fluid, bleeding, cramping, or fever. If after 48 hours these signs have not been noted, then she may continue her usual activities except for any form of vaginal penetration. If, however, the gush of fluid is accompanied or followed by bleeding and pain, or if fever ensues, abortion should be considered inevitable and the uterus emptied.
Incomplete abortion is diagnosed when the placenta, in whole or in part, is retained in the uterus but the fetus has been passed. Bleeding usually accompanies an incomplete abortion and may be quite significant in those pregnancies that are more advanced. The embryo–fetus and placenta are likely to be expelled together in abortions occurring before 10 weeks’ gestation.
Missed abortion is defined as retention of dead products of conception in utero for several weeks. After fetal death, there may or may not be vaginal bleeding or other symptoms. The uterus may remain stationary in size, and mammary changes usually regress. Most missed abortions terminate spontaneously; however, after prolonged retention of the dead fetus, a serious coagulation defect may develop. The pathogenesis and treatment of coagulation defects and any attendant hemorrhage in instances of prolonged retention of a dead fetus are discussed in Chapter 31.
The most accepted definition of recurrent abortion requires three or more consecutive spontaneous abortions. Repeated spontaneous abortions are likely to be chance phenomena in the majority of cases. Approximately 1 to 2 percent of women of reproductive age will experience three or more spontaneous, consecutive abortions, and as many as 5 percent will have two or more recurrent abortions. Women with three or more such abortions are considered at increased risk to have a chromosomal anomaly, endocrinological disorder, or an altered immune system. Women with three or more spontaneous abortions are at increased risk in a subsequent pregnancy for preterm delivery, placenta previa, breech presentation, and fetal malformation. With the exception of women who have antiphospholipid antibodies or an incompetent cervix, between 70 and 85 percent of women with recurrent abortion can expect a successful subsequent pregnancy outcome regardless of treatment.
Therapeutic abortion is the medical or surgical termination of a pregnancy before the time of fetal viability in order to prevent serious or permanent bodily injury to the mother. Indications include persistent heart disease after cardiac decompensation, advanced hypertensive vascular disease, and invasive carcinoma of the cervix. In addition to medical and surgical disorders that may be an indication for termination of pregnancy, there are others. Most authorities consider termination appropriate in cases of rape or incest. Another commonly cited indication is to prevent a viable birth of a fetus with a significant anatomical or mental deformity. The seriousness of fetal deformities is wide ranging and frequently defies social or legal classification.
Elective or voluntary abortion is the interruption of pregnancy before viability at the request of the woman but not for reasons of impaired maternal health or fetal disease. Most abortions done today fall into this category; in fact, there is approximately one elective abortion for every four live births in the United States. The legality of elective abortion was established by the 1973 United States Supreme Court decision in Roe v. Wade.
There are a variety of fetal and maternal etiologies for spontaneous abortions, and these are summarized next.
The most common morphological finding in early spontaneous abortions is an abnormality of development of the zygote, embryo, early fetus, or at times the placenta, and chromosomal abnormalities are common. For example, 60 percent of aborted embryos have chromosomal abnormalities. Autosomal trisomy is the most frequently identified chromosomal abnormality associated with first-trimester abortions. Trisomies 13, 16, 18, 21, and 22 are the most common of these. Monosomy X (45,X) is the next most common chromosomal abnormality and is compatible with live born females (e.g., Turner syndrome). Triploidy is often associated with hydropic placental degeneration. Incomplete hydatidiform moles may have fetal development that is triploid or trisomic for chromosome 16. Tetraploid fetuses are rarely live born and are most often aborted in the early first trimester. Three-fourths of aneuploid abortions occur before 8 weeks, whereas euploid abortions peak at about 13 weeks. The incidence of euploid abortions increases dramatically after the maternal age of 35 years.
Spontaneous abortions have been independently associated with maternal human immunodeficiency virus-1 (HIV-1) antibody, maternal syphilis seroreactivity, and vaginal colonization with group B streptococci. There is also evidence to support a role for Mycoplasma hominis and Ureaplasma urealyticum in abortion. Chronic infections with organisms such as Brucella abortus, Campylobacter fetus, Toxoplasma gondii, Listeria monocytogenes, or Chlamydia trachomatis have not been proven to be associated with spontaneous abortion.
Clinical hypothyroidism is not associated with an increased incidence of abortion. However, women with thyroid autoantibodies may be at an increased risk. Spontaneous abortion and major congenital malformations are both increased in women with insulin-dependent diabetes, and the risk is related to the degree of metabolic control. Insufficient progesterone secretion by the corpus luteum or placenta has been associated with an increased incidence of abortion; however, this may be a consequence rather than a cause for early pregnancy loss.
There is no conclusive evidence that dietary deficiency of any one nutrient or moderate deficiency of all nutrients is an important cause of abortion.
Smoking has been associated with an increased risk for euploid abortion. For women who smoke more than 14 cigarettes a day, the risk is approximately twofold. Frequent alcohol use during the first 8 weeks of pregnancy may result in both spontaneous abortion and fetal malformations. The abortion rate is doubled in women who drink twice weekly and tripled in women who consume alcohol daily. Coffee consumption at more than four cups per day appears to slightly increase the risk of spontaneous abortion.
There is no evidence to support the idea that oral contraceptives or spermicidal agents used in contraceptive creams and jellies are associated with an increased incidence of abortion. Intrauterine devices, however, are associated with an increased incidence of septic abortion after contraceptive failure.
In sufficient doses, radiation is a recognized abortifacient. Current evidence suggests that there is no increased risk of abortion from a radiation dose of less than 5 rad. In most instances, however, there is little information to indict any specific environmental agent.
Two primary pathophysiological models for immune-related spontaneous abortion are the autoimmune theory (immunity against self) and the alloimmune theory (immunity against another person). Up to 15 percent of women with recurrent pregnancy loss have autoimmune factors. The best-established autoimmune disorder associated with spontaneous abortion is the antiphospholipid antibody syndrome. The mechanism of pregnancy loss in these women is thought to involve placental thrombosis and infarction (see Chapter 54). Antiphospholipid antibodies are acquired antibodies targeted against a phospholipid. The IgG and IgM antiphospholipid antibodies that have been found to be most reliable are lupus anticoagulant (LAC), anticardiolipin antibody (ACA), and anti-beta-2 glycoprotein 1.
A number of women with recurrent pregnancy loss have been diagnosed with an alloimmune cause. The validity of this diagnosis remains doubtful, and immunotherapy for recurrent abortion should be considered experimental.
There have been numerous reports of an association between spontaneous abortions and inherited thrombophilias such as deficiencies of protein C, protein S, and antithrombin III. Factor V Leiden mutation and hyperhomocysteinemia have also been associated with pregnancy loss. Although controversial, heparin and aspirin therapy is thought by many to improve pregnancy outcomes (see Chapter 53).
Uterine defects may be either developmental or acquired. Acquired defects such as large or multiple uterine leiomyomas usually do not cause abortion unless located subserosal or in the lower uterine segment. Uterine synechiae (Asherman syndrome) are caused by destruction of large areas of endometrium by curettage and have been associated with spontaneous abortion. Developmental uterine defects are the consequences of abnormal Müllerian duct formation or fusion, or may be induced by in utero exposure to diethylstilbestrol. Some types, such as uterine septa, may be associated with abortions.
An incompetent cervix is characterized by relatively painless cervical dilatation in the second trimester or perhaps early in the third trimester, with prolapse and ballooning of membranes into the vagina, followed by rupture of membranes and expulsion of an immature fetus (see Chapter 36).
There is no evidence that surgery performed early in pregnancy causes abortion. However, peritonitis does increase the risk of abortion.
There is a variety of surgical and medical methods for treatment of spontaneous abortion as well as terminations performed under other circumstances, and these are summarized in Table 1-1. The most commonly used techniques are summarized next; please see Williams Obstetrics, 23rd ed., Chapter 9, “Abortion,” for the other methods presented in Table 1-1.
TABLE 1-1. Abortion Techniques
Dilatation and Curettage
Surgical abortion before 14 weeks is performed by first dilating the cervix (Figure 1-1) and then evacuating the pregnancy by mechanically scraping out the contents (sharp curettage, Figure 1-2), by vacuum aspiration (suction curettage), or both. After 16 weeks, dilatation and evacuation (D & E) is performed. This consists of wide cervical dilatation followed by mechanical destruction and evacuation of the fetal parts. With complete removal of the fetus, a large-bore vacuum curette is used to remove the placenta and remaining tissue. A dilatation and extraction (D & X) is similar to a D & E except that suction evacuation of the intracranial contents after delivery of the fetal body through the dilated cervix facilitates extraction and minimizes uterine or cervical injury.
FIGURE 1-1 Dilatation of cervix with Hegar dilator. Note that the fourth and fifth fingers rest against the perineum and buttocks, lateral to the vagina. This maneuver is a most important safety measure because if the cervix relaxes abruptly, these fingers prevent a sudden and uncontrolled thrust of the dilator, a common cause of uterine perforation. (Reproduced, with permission, from Cunningham FG, Leveno KJ, Bloom SL, et al (eds). Williams Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2010.)
FIGURE 1-2 Introduction of a sharp curet. The instrument is held with the thumb and forefinger. In the upward movement of the curette, only the strength of these two fingers should be used. (Reproduced, with permission, from Cunningham FG, Leveno KJ, Bloom SL, et al (eds). Williams Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2010.)
Laminaria tents are commonly used to help dilate the cervix prior to surgical abortion (Figure 1-3). These devices draw water from cervical tissues and allow the cervix to soften and dilate. Synthetic hygroscopic dilators have also been used. Lamicel is a polyvinyl alcohol polymer sponge impregnated with anhydrous magnesium sulfate. Trauma from mechanical dilatation can be minimized by using hygroscopic dilators. Women who have an osmotic dilator placed prior to an elective abortion but then change their minds generally do not suffer infectious morbidity after the dilators are removed.
FIGURE 1-3 Insertion of laminaria prior to dilatation and curettage. A. Laminaria immediately after being appropriately placed with its upper end just through the internal os. B. Several hours later the laminaria is now swollen, and the cervix is dilated and softened. C. Laminaria inserted too far through the internal os; the laminaria may rupture the membranes. (Reproduced, with permission, from Cunningham FG, Leveno KJ, Bloom SL, et al (eds). Williams Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2010.)
Antimicrobial prophylaxis should be provided to all women undergoing a transcervical surgical abortion. One convenient, inexpensive, and effective regimen is doxycycline, 100 mg orally before the procedure and 200 mg orally after. Treatment of D-negative women after abortion with anti-D immunoglobulin is recommended, because about 5 percent of D-negative women become sensitized after an abortion. Both ultrasound and tissue examination are important in women undergoing surgical first-trimester abortion.
Accidental uterine perforation may occur during sounding of the uterus, dilatation, or curettage. Two important determinants of this complication are the skill of the physician and the position of the uterus, with a much greater likelihood of perforation if the uterus is retroverted. Accidental uterine perforation is recognized easily, as the instrument passes without resistance deep into the pelvis. Observation may be sufficient therapy if the uterine perforation is small, as when produced by a uterine sound or narrow dilator.
Considerable intra-abdominal damage can be caused by instruments passed through a uterine defect into the peritoneal cavity. This is especially true for suction and sharp curets. In this circumstance, laparotomy to examine the abdominal contents, especially the bowel, is the safest course of action.
The likelihood of complications—including uterine perforation, cervical laceration, hemorrhage, incomplete removal of the fetus and placenta, and infection—increases after the first trimester. For this reason, curettage or vacuum aspiration should be performed before 14 weeks. In the absence of maternal systemic disease, pregnancies are usually terminated by curettage or by evacuation or extraction without hospitalization. When abortion is not performed in a hospital setting, it is imperative that capabilities for effective cardiopulmonary resuscitation are available, and that immediate access to hospitalization is possible. Some women may develop cervical incompetence or uterine synechiae following dilatation and curettage. The possibility of these complications should be explained to those contemplating abortion. In general, their risk is very slight. Unfortunately, more advanced abortion performed by curettage may induce sudden, severe consumptive coagulopathy, which can prove fatal.
Early medical abortion is highly effective—90 to 98 percent of women will not require surgical intervention. According to the American College of Obstetricians and Gynecologist (Medical management of abortion. Practice Bulletin No. 67, October 2005, reaffirmed 2011), outpatient medical abortion is an acceptable alternative to surgical abortion in appropriately selected women with pregnancies of less than 49 days’ gestation. Three medications for early medical abortion have been widely studied and used: the antiprogestin mifepristone (RU486 not readily available in the United States), the antimetabolite methotrexate, and the prostaglandin misoprostol. These agents cause abortion by increasing uterine contractility, either by reversing the progesterone-induced inhibition of contraction (mifepris-tone and methotrexate) or by stimulating the myometrium directly (misoprostol).
Various dosing schemes have proven effective (Table 1-2). Mifepristone and methotrexate are administered initially, and followed after some time interval by misoprostol. Women contemplating medical abortion should receive thorough counseling regarding the risks, benefits, and requirements of both medical and surgical approaches.
TABLE 1-2. Regimens for Medical Termination of Early Pregnancy
Invasive means of second-trimester medical abortion have long been available (see Table 1-1). In the past decade, however, the ability to safely and effectively accomplish noninvasive second-trimester abortion has evolved considerably. Principal among these noninvasive methods are high-dose intravenous oxytocin and vaginal prostaglandin administration. Regardless of method, laminaria placement as shown in Figure 1-3 will shorten the duration.
Successful induction of second-trimester abortion is possible with high doses of oxytocin administered in small volumes of intravenous fluids. One regimen is to add ten 1-mL ampules of oxytocin (10 IU/mL) to 1000 mL of lactated Ringer solution. This solution contains 100 mU oxytocin per mL. An intravenous infusion is started at 0.5 mL/min (50 mU/min). The rate of infusion is increased at 15- to 30-minute intervals up to a maximum rate of 2 mL/min (200 mU/min). If effective contractions are not established at this infusion rate, the concentration of oxytocin is increased in the infused solution. It is safest to discard all but 500 mL of the remaining solution, which contains a concentration of 100 mU oxytocin per mL. To this 500 mL is added an additional five ampules of oxytocin. The resulting solution now contains 200 mU/mL, and the rate of infusion is reduced to 1 mL/min (200 mU/min). A resumption of a progressive rate increase is commenced up to a rate of 2 mL/min (400 mU/min) and left at this rate for an additional 4 to 5 hours, or until the fetus is expelled. With concentrated oxytocin, careful attention must be directed to the frequency and intensity of uterine contractions, because each increase in infusion rate markedly increases the amount of oxytocin infused. If the initial induction is unsuccessful, serial inductions on a daily basis for 2 to 3 days are almost always successful. The chance of a successful induction with high-dose oxytocin is enhanced greatly by the use of hygroscopic dilators such as laminaria tents inserted the night before.
Because of shortcomings of other medical methods of inducing abortion, pros-taglandins and their analogs are used extensively to terminate pregnancies, especially in the second trimester. Compounds commonly used are prostaglandin E2, prostaglandin F2α, and certain analogs, especially 15-methylprostaglandin F2α methyl ester, prostaglandin E1-methyl ester (gemeprost), and misoprostol. Prostaglandin regimens used for midtrimester abortion are shown in Table 1-3.
TABLE 1-3. Prostaglandin Analog Regimens Used for Midtrimester Abortion
For further reading in Williams Obstetrics, 23rd ed.,
see Chapter 9, “Abortion.”