More than 80 percent of spontaneous abortions occur within the first 12 weeks of gestation. With first-trimester losses, death of the embryo or fetus nearly always precedes spontaneous expulsion. Death is usually accompanied by hemorrhage into the decidua basalis. This is followed by adjacent tissue necrosis that stimulates uterine contractions and expulsion. An intact gestational sac is usually filled with fluid and may or may not contain an embryo or fetus. Thus, the key to determining the cause of early miscarriage is to ascertain the cause of fetal death. In contradistinction, in later pregnancy losses, the fetus usually does not die before expulsion, and thus other explanations are sought.
Statistics regarding the incidence of spontaneous abortion vary according to the diligence used for its recognition. Wilcox and colleagues (1988) studied 221 healthy women through 707 menstrual cycles and found that 31 percent of pregnancies were lost after implantation. They used highly specific assays for minute concentrations of maternal serum β-hCG and reported that two thirds of these early losses were clinically silent.
Currently, there are factors known to influence clinically apparent spontaneous abortion, however, it is unknown if these same factors affect clinically silent miscarriages. By way of example, the rate of clinical miscarriages is almost doubled when either parent is older than 40 years (Gracia, 2005; Kleinhaus, 2006). But, it is not known if clinically silent miscarriages are similarly affected by parental age.
As shown in Table 18-1, approximately half of miscarriages are anembryonic, that is, with no identifiable embryonic elements. Less accurately, the term blighted ovum may be used (Silver, 2011). The other 50 percent are embryonic miscarriages, which commonly display a developmental abnormality of the zygote, embryo, fetus, or at times, the placenta. Of embryonic miscarriage, half of these—25 percent of all abortuses—have chromosomal anomalies and thus are aneuploid abortions. The remaining cases are euploid abortions, that is, carrying a normal chromosomal complement.
Table 18-1Chromosomal Findings in First-Trimester Abortuses ||Download (.pdf) Table 18-1 Chromosomal Findings in First-Trimester Abortuses
|Chromosomal Studies ||Incidence Range (%) |
|Embryonic ||~50 |
|Euploid || |
|46,XY and 46,XX ||45 to 55 |
|Aneuploid || |
|Autosomal trisomy ||22 to 32 |
|Monosomy X (45,X) ||5 to 20 |
|Triploidy ||6 to 8 |
|Tetraploidy ||2 to 4 |
|Structural anomaly ||2 |
|Anembryonic (blighted ovum) ||~50 |
Both abortion rates and chromosomal anomalies decrease with advancing gestational age. As shown in Figure 18-1, 50 percent of embryonic abortions are aneuploid, but chromosomal abnormalities are found in just a third of second-trimester fetal losses and in only 5 percent of third-trimester stillbirths. Aneuploid abortion occurs at earlier gestational ages. Kajii and associates (1980) noted that 75 percent of aneuploid abortions occurred by 8 weeks. Of these, 95 percent of chromosomal abnormalities are caused by maternal gametogenesis errors, and 5 percent by paternal errors (Jacobs, 1980). Some found most common are listed in Table 18-1.
Frequency of chromosomal anomalies in abortuses and stillbirths during each trimester. Approximate percentages for each group are shown. (Data from Eiben, 1990; Fantel, 1980; Warburton, 1980.)
With first-trimester miscarriages, autosomal trisomy is the most frequently identified chromosomal anomaly. Although most trisomies result from isolated nondisjunction, balanced structural chromosomal rearrangements are found in one partner in 2 to 4 percent of couples with recurrent miscarriages. Trisomies have been identified in abortuses for all except chromosome number 1, and those with 13, 16, 18, 21, and 22 are most common. A previous miscarriage increases the baseline risk for aneuploidy in a subsequent fetus from 1.4 to 1.7 percent (Bianco, 2006). With two or three previous miscarriages, the risk increases to 1.8 and 2.2 percent, respectively.
Monosomy X (45,X) is the single most frequent specific chromosomal abnormality. This is Turner syndrome, which usually results in abortion, but liveborn females are described (Chap. 13, Monosomy). Conversely, autosomal monosomy is rare and incompatible with life.
Triploidy is often associated with hydropic or molar placental degeneration (Chap. 20, Clinical Findings). The fetus within a partial hydatidiform mole frequently aborts early, and the few carried longer are all grossly deformed. Advanced maternal and paternal age do not increase the incidence of triploidy. Tetraploid fetuses most often abort early in gestation, and they are rarely liveborn. Last, chromosomal structural abnormalities infrequently cause abortion.
Chromosomally normal fetuses abort later than those that are aneuploid. Specifically, the rate of euploid abortions peaks at approximately 13 weeks (Kajii, 1980). In addition, the incidence of euploid abortions increases dramatically after maternal age exceeds 35 years (Stein, 1980).
The causes of euploid abortions are poorly understood, but various medical disorders, environmental conditions, and developmental abnormalities have been implicated. One example is the well-known influence of maternal age just described.
Some common viral, bacterial, and other infectious agents that invade the normal human can cause pregnancy loss. Many are systemic and infect the fetoplacental unit by blood-borne organisms. Others may infect locally through genitourinary infection or colonization. However, despite the numerous infections acquired in pregnancy, these uncommonly cause early abortion. Brucella abortus, Campylobacter fetus, and Toxoplasma gondii infections cause abortion in livestock, but their role in human pregnancy is less clear (Feldman, 2010; Hide, 2009; Mohammad, 2011; Vilchez, 2014). There appear to be no abortifacient effects of infections caused by Listeria monocytogenes, parvovirus, cytomegalovirus, or herpes simplex virus (Brown, 1997; Feldman, 2010). One possible exception is infection with Chlamydia trachomatis, which was found to be present in 4 percent of abortuses compared with < 1 percent of controls (Baud, 2011). Another is polymicrobial infection from periodontal disease that has been linked with a two- to fourfold increased risk (Holbrook, 2004; Moore, 2004; Xiong, 2007).
Data concerning a link between some other infections and increased abortion are conflicting. Examples are Mycoplasma and Ureaplasma (Quinn, 1983a,b; Temmerman, 1992). Another is an association with human immunodeficiency virus (HIV) (Quinn, 1983a,b; van Benthem, 2000). Oakeshott and coworkers (2002) reported an association between second-, but not first-, trimester miscarriage and bacterial vaginosis.
In general, early abortions are rarely due to chronic wasting diseases such as tuberculosis or carcinomatosis. There are a few specific disorders possibly linked with increased early pregnancy loss. Those associated with diabetes mellitus and thyroid disease are discussed subsequently. Another example is celiac disease, which has been reported to cause recurrent abortions as well as both male and female infertility (Sharshiner, 2013; Sher, 1994). Unrepaired cyanotic heart disease is likely a risk for abortion, and in some, this may persist after repair (Canobbio, 1996). Eating disorders—anorexia nervosa and bulimia nervosa—have been linked with subfertility, preterm delivery, and fetal-growth restriction. Their association with miscarriage, however, is less well studied (Andersen, 2009; Sollid, 2004). Inflammatory bowel disease and systemic lupus erythematosus may increase the risk (Al Arfaj, 2010; Khashan, 2012). Chronic hypertension does not appear to confer significant risk (Ankumah, 2013). Perhaps related, women with a history of recurrent miscarriages were reported to be at increased risk for fetal-growth restriction (Catov, 2008). Another possible link with vascular disease is that women with multiple miscarriages are more likely to later suffer a myocardial infarction (Kharazmi, 2011).
Only a few medications have been evaluated concerning a role with early pregnancy loss. Oral contraceptives or spermicidal agents used in contraceptive creams and jellies are not associated with an increased miscarriage rate. Similarly, nonsteroidal antiinflammatory drugs or ondansetron are not linked (Edwards, 2012; Pasternak, 2013). A pregnancy with an intrauterine device (IUD) in situ has an increased risk of abortion and specifically of septic abortion (Chap. 38, Insertion). With the newer IUDs, Moschos and Twickler (2011) reported that only 6 of 26 intact pregnancies aborted before 20 weeks. Finally, studies have shown no increase in pregnancy loss rates with meningococcal conjugate or trivalent inactivated influenza vaccines (Irving, 2013; Zheteyeva, 2013).
Therapeutic doses of radiation are undeniably abortifacient, but doses that cause abortion are not precisely known (Chap. 46, Ionizing Radiation). According to Brent (2009), exposure to < 5 rads does not increase the risk.
Cancer survivors who were previously treated with abdominopelvic radiotherapy may later be at increased risk for miscarriage. Wo and Viswanathan (2009) reported an associated two- to eightfold increased risk for miscarriages, low-birthweight and growth-restricted infants, preterm delivery, and perinatal mortality in women previously treated with radiotherapy. Hudson (2010) found an associated increased risk for miscarriage in those given radiotherapy and chemotherapy in the past for a childhood cancer.
The effects of chemotherapy in causing abortion are not well defined (Chap. 12, Antimicrobial Drugs). Particularly worrisome are women with an early normal gestation erroneously treated with methotrexate for an ectopic pregnancy (Chap. 19, Medical Management). Ina report of eight such cases, two viable-size fetuses had multiple malformations. In the remaining six cases, three each had a spontaneous or induced abortion (Nurmohamed, 2011).
The abortifacient effects of uncontrolled diabetes are well-known. Optimal glycemic control will mitigate much of this loss and is discussed in Chapters 8 (Medical History) and 57 (Fetal Effects).Spontaneous abortion and major congenital malformation rates are both increased in women with insulin-dependent diabetes. This is directly related to the degree of periconceptional glycemic and metabolic control.
These have long been suspected to cause early pregnancy loss and other adverse pregnancy outcomes. Severe iodine deficiency, which is infrequent in developed countries, has been associated with increased miscarriage rates (Castañeda, 2002). Varying degrees of thyroid hormone insufficiency are common in women. Although the worst—overt hypothyroidism—is infrequent in pregnancy, subclinical hypothyroidism has an incidence of 2 to 3 percent (Casey, 2005; Garber, 2012). Both are usually caused by autoimmune Hashimoto thyroiditis, in which both incidence and severity accrue with age. Despite this common prevalence, any increased risks for miscarriage due to hypothyroidism are still unclear (Krassas, 2010; Negro, 2010). That said, De Vivo (2010) reported that subclinical thyroid hormone deficiency may be associated with very early pregnancy loss.
The prevalence of abnormally high serum levels of antibodies to thyroid peroxidase or thyroglobulin is nearly 15 percent in pregnant women (Abbassi-Ghanavati, 2010; Haddow, 2011). Although most of these women are euthyroid, those with clinical hypothyroidism tend to have higher concentrations of antibodies. Even in euthyroid women, however, antibodies are a marker for increased miscarriage (Benhadi, 2009; Chen, 2011; Thangaratinam, 2011). This has been confirmed by two prospective studies, and preliminary data from one suggest that thyroxine supplementation decreases this risk (Männistö, 2009; Negro, 2006). Effects associated with thyroid disorders in women with recurrent miscarriage are considered further on Immunological Factors.
The risk of miscarriage caused by surgery is not well studied. There is extensive interest in pregnancy outcomes following bariatric surgery, because as discussed on Diabetes Mellitus, obesity is an uncontested risk factor for miscarriage. However, currently, it is not known if this risk is mitigated by weight-reduction surgery (Guelinckx, 2009).
It is likely that uncomplicated surgical procedures performed during early pregnancy do not increase the risk for abortion (Mazze, 1989). Ovarian tumors can generally be resected without causing miscarriage (Chap. 63, Sonography). An important exception involves early removal of the corpus luteum or the ovary in which it resides. If performed before 10 weeks' gestation, supplemental progesterone should be given. Between 8 and 10 weeks, a single 150-mg intramuscular injection of 17-hydroxyprogesterone caproate is given at the time of surgery. If between 6 to 8 weeks, then two additional 150-mg injections should be given 1 and 2 weeks after the first. Other progesterone regimens include: (1) oral micronized progesterone (Prometrium), 200 or 300 mg orally once daily, or (2) 8-percent progesterone vaginal gel (Crinone) given intravaginally as one premeasured applicator daily plus micronized progesterone 100 or 200 mg orally once daily continued until 10 weeks' gestation.
Trauma seldom causes first-trimester miscarriage, and although Parkland Hospital is a busy trauma center, this is an infrequent association. Major trauma—especially abdominal—can cause fetal loss, but is more likely as pregnancy advances (Chap. 47, Trauma).
Extremes of nutrition—severe dietary deficiency and morbid obesity—are associated with increased miscarriage risks. Dietary quality may also be important, as this risk may be reduced in women who consume fresh fruit and vegetables daily (Maconochie, 2007).
Sole deficiency of one nutrient or moderate deficiency of all does not appear to increase risks for abortion. Even in extreme cases—for example, hyperemesis gravidarum—abortion is rare (Maconochie, 2007). Other examples discussed on Maternal Factors are anorexia and bulimia nervosa. Importantly, Bulik and colleagues (2010) reported that half of pregnancies in women with anorexia nervosa were unplanned.
Obesity is associated with a litany of adverse pregnancy outcomes (Chap. 48, Maternal Weight Gain and Energy Requirement). These include subfertility and an increased risk of miscarriage and recurrent abortion (Jarvie, 2010; Lashen, 2004; Satpathy, 2008). In a study of 6500 women who conceived with in vitro fertilization (IVF), live birth rates were reduced progressively for each body mass index (BMI) unit increase (Bellver, 2010a). As noted earlier, although the risks for many adverse late-pregnancy outcomes are decreased after bariatric surgery, any salutary effects on the miscarriage rate are not clear (Guelinckx, 2009).
Social and Behavioral Factors
Lifestyle choices reputed to be associated with an increased miscarriage risk are most commonly related to chronic and especially heavy use of legal substances. The most common used is alcohol, with its potent teratogenic effects discussed in Chapter 12 (Known and Suspected Teratogens). That said, an increased miscarriage risk is only seen with regular or heavy use (Floyd, 1999; Maconochie, 2007). In fact, low-level alcohol consumption does not significantly increase the abortion risk (Cavallo, 1995; Kesmodel, 2002).
At least 15 percent of pregnant women admit to cigarette smoking (Centers for Disease Control and Prevention, 2013). It seems intuitive, but unproven, that cigarettes could cause early pregnancy loss by a number of mechanisms that cause adverse late-pregnancy outcomes (Catov, 2008).
Excessive caffeine consumption—not well defined—has been associated with an increased abortion risk. There are reports that heavy intake of approximately five cups of coffee per day—about 500 mg of caffeine—slightly increases the abortion risk (Armstrong, 1992; Cnattingius, 2000; Klebanoff, 1999). Studies of ‘moderate’—less than 200 mg daily—did not increase the risk (Savitz, 2008; Weng, 2008). Currently, the American College of Obstetricians and Gynecologists (2013b) has concluded that moderate consumption likely is not a major abortion risk and that any associated risk with higher intake is unsettled. Adverse effects of illicit drugs are discussed in Chapter 12 (Herbal Remedies).
Occupational and Environmental Factors
It is intuitive to limit exposure of pregnant women to any toxin. That said, although some environmental toxins such as benzene are implicated in fetal malformations, data with miscarriage risk is less clear (Lupo, 2011). The major reason is that it is not possible to accurately assess environmental exposures. Earlier reports that implicated some chemicals as increasing miscarriage risk include arsenic, lead, formaldehyde, benzene, and ethylene oxide (Barlow, 1982). More recently, there is evidence that DDT—dichlorodiphenyltrichloroethane—may cause excessive miscarriage rates (Eskenazi, 2009). In fact, use of DDT-containing insecticides had been suspended. But in 2006, it was again and is still endorsed by the World Health Organization (2011) for mosquito control for malaria prevention.
There are even fewer studies of occupational exposures and abortion risks. In a follow-up of the Nurses Health Study II, Lawson and associates (2012) reported slightly increased miscarriage risks in nurses exposed to antineoplastic drugs, sterilizing agents, and x-rays. Some of these found that exposure to video display terminals or to ultrasound did not increase miscarriage rates (Schnorr, 1991; Taskinen, 1990). Increased miscarriage risk was found for dental assistants exposed to more than 3 hours of nitrous oxide daily if there was no gas-scavenging equipment (Boivin, 1997; Rowland, 1995). Conclusions from a metaanalysis were that there is a small incremental risk for spontaneous abortion in women who worked with cytotoxic antineoplastic chemotherapeutic agents (Dranitsaris, 2005).
The immune tolerance of the mother to the paternal-haploid fetal combination remains enigmatic (Calleja-Agius, 2011; Williams, 2012). This is discussed in greater detail in Chapter 5 (Breaks in the Placental “Barrier”). There is, however, an increased risk for early pregnancy loss with some immune-mediated disorders. The most potent of these are antiphospholipid antibodies directed against binding proteins in plasma (Erkan, 2011). These along with clinical and laboratory findings provide criteria for the antiphospholipid antibody syndrome—APS (American College of Obstetricians and Gynecologists, 2012). Because associated pregnancy loss can be repetitive, recurrent miscarriage due to APS is discussed on Immunological Factors.
Although thrombophilias were initially linked to various pregnancy outcomes, most putative associations have been refuted. Currently, the American College of Obstetricians and Gynecologists (2013a) is of the opinion that there is not a definitive causal link between these thrombophilias and adverse pregnancy outcomes in general, and abortion in particular.
Various inherited and acquired uterine defects are known to cause both early and late recurrent miscarriages, and they are considered on Recurrent Miscarriage.
These factors in the genesis of miscarriage are not well studied. Chromosomal abnormalities in sperm reportedly had an increased abortion risk (Carrell, 2003). Increasing paternal age was significantly associated with increased risk for abortion in the Jerusalem Perinatal Study (Kleinhaus, 2006). This risk was lowest before age 25 years, after which it progressively increased at 5-year intervals.
Clinical Classification of Spontaneous Abortion
The clinical diagnosis of threatened abortion is presumed when bloody vaginal discharge or bleeding appears through a closed cervical os during the first 20 weeks (Hasan, 2009). Bleeding in early pregnancy must be differentiated from implantation bleeding, which some women have at the time of the expected menses (Chap. 5, The Trophoblast). Almost a fourth of women develop clinically significant bleeding during early gestation that may persist for days or weeks. With miscarriage, bleeding usually begins first, and cramping abdominal pain follows hours to days later. There may be low-midline clearly rhythmic cramps; persistent low backache with pelvic pressure; or dull and midline suprapubic discomfort. Bleeding is by far the most predictive risk factor for pregnancy loss (Eddleman, 2006). Overall, approximately half will abort, but this risk is substantially less if there is fetal cardiac activity (Tongsong, 1995).
Even if miscarriage does not follow early bleeding, the risk for later adverse pregnancy outcomes is increased as shown in Table 18-2. In the study of almost 1.8 million pregnancies from the Danish National Patient Registry, there was a threefold risk for many of these pregnancy complications.
Table 18-2Adverse Outcomes That are Increased in Women with Threatened Abortion ||Download (.pdf) Table 18-2 Adverse Outcomes That are Increased in Women with Threatened Abortion
|Maternal ||Perinatal |
|Placenta previa ||Preterm ruptured membranes |
|Placental abruption ||Preterm birth |
|Manual removal of placenta ||Low-birthweight infant |
|Cesarean delivery ||Fetal-growth restriction |
| ||Fetal and neonatal death |
Threatened Abortion versus Ectopic Pregnancy
Every woman with an early pregnancy, vaginal bleeding, and pain should be evaluated. The primary goal is prompt diagnosis of an ectopic pregnancy. As discussed in Chapter 19 (Beta Human Chorionic Gonadotropin), serial quantitative serum β-hCG and progesterone levels and transvaginal sonography are used to ascertain if there is an intrauterine live fetus. Because these are not 100-percent accurate to confirm early fetal death or location, repeat evaluations are often necessary. serum hCG levels in women with bleeding who went on to have an early miscarriage are shown in Figure 18-2 and in Table 19-1 (Beta Human Chorionic Gonadotropin). Values for women with early pregnancy bleeding who went on to have a normal pregnancy are shown in Figure 18-3. Several predictive models have been described (Barnhart, 2010; Condous, 2007; Connolly, 2013). With a robust uterine pregnancy, serum β-hCG levels should increase at least 53 to 66 percent every 48 hours (Barnhart, 2004a; Kadar, 1982). Serum progesterone concentrations < 5 ng/mL suggest a dying pregnancy, whereas values > 20 ng/mL support the diagnosis of a healthy pregnancy.
Composite curve describing decline in serial human chorionic gonadotropin (hCG) values starting at a level of 2000 mIU/mL following early spontaneous miscarriage. The dashed line is the predicted curve based on the summary of data from all women. The colored area within the dashed lines represents the 95-percent confidence intervals. (Data from Barnhart, 2004a.)
Composite curve of increasing serum levels of beta-human chorionic gonadotropin (β-hCG) in women with early bleeding and subsequent normal pregnancy. (Data from Barnhart, 2004b.)
Transvaginal sonography is used to locate the pregnancy and determine if the fetus is alive. If this cannot be done, then pregnancy of unknown location is diagnosed (Chap. 19, Beta Human Chorionic Gonadotropin). The gestational sac—an anechoic fluid collection that represents the exocoelomic cavity—may be seen by 4.5 weeks (Fig. 9-3, Initial Prenatal Evaluation). At this same time, β-hCG levels are generally considered to be 1500 to 2000 mIU/mL (Barnhart, 1994; Timor-Tritsch, 1988). Connolly and colleagues (2013) observed that this value could be as low as 390 mIU/mL, but also noted that a threshold as high as 3500 mIU/mL may be needed to identify the gestational sac in 99 percent of cases.
Another caveat is that a gestational sac may appear similar to other intrauterine fluid accumulations—the so-called pseudogestational sac (Fig. 19-5, Transvaginal Sonography). This pseudosac may be seen with ectopic pregnancy and is easier to exclude once a yolk sac is seen. Typically, the yolk sac is visible by 5.5 weeks and with a mean gestational-sac diameter of 10 mm. Thus, the diagnosis of a uterine pregnancy should be made cautiously if the yolk sac is not yet seen (American College of Obstetricians and Gynecologists, 2011e).
At 5 to 6 weeks, a 1- to 2-mm embryo adjacent to the yolk sac can be seen (Daya, 1993). Absence of an embryo in a sac with a mean sac diameter of 16 to 20 mm suggests a dead fetus (Levi, 1988; Nyberg, 1987). Finally, fetal cardiac activity can be detected at 6 to 6.5 weeks with an embryonic length of 1 to 5 mm and a mean sac diameter of 13 to 18 mm. A 5-mm embryo without cardiac activity is likely dead (Goldstein, 1992; Levi, 1990).
There are various management schemes derived from these findings. At Parkland Hospital, to ensure that live intrauterine pregnancies are not interrupted, we define the threshold of embryo fetal death based on values two standard deviations from the mean. Thus, an anembryonic gestation is diagnosed when the mean gestational sac diameter measures ≥ 20 mm and no embryo is seen. Embryonic death is also diagnosed if an embryo measuring ≥ 10 mm has no cardiac activity.
Acetaminophen-based analgesia will help relieve discomfort from cramping. If uterine evacuation is not indicated, bed rest is often recommended but does not improve outcomes. Neither has treatment with a host of medications that include chorionic gonadotropin (Devaseelan, 2010). With persistent or heavy bleeding, the hematocrit is determined. If there is significant anemia or hypovolemia, then pregnancy evacuation is generally indicated. In these cases in which there is a live fetus, some choose transfusion and further observation.
With spontaneous miscarriage, 2 percent of Rh D-negative women will become alloimmunized if not provided passive isoimmunization. With an induced abortion, this rate may reach 5 percent. The American College of Obstetricians and Gynecologists (2013c) recommends anti-Rh0 (D) immunoglobulin given as 300 μg intramuscularly (IM) for all gestational ages, or 50 μg IM for pregnancies ≤ 12 weeks and 300 μg for ≥ 13 weeks.
With threatened abortion, immunoglobulin prophylaxis is controversial because of sparse evidence-based data (American College of Obstetricians and Gynecologists, 2013c; Hannafin, 2006; Weiss, 2002). That said, some choose to administer anti-D immunoglobulin up to 12 weeks' gestation for a threatened abortion and a live fetus. At Parkland Hospital, we administer a 50-μg dose to all Rh D-negative women with first-trimester bleeding.
In the first trimester, gross rupture of the membranes along with cervical dilatation is nearly always followed by either uterine contractions or infection. A gush of vaginal fluid during the first half of pregnancy usually has serious consequences. In some cases not associated with pain, fever, or bleeding, fluid may have collected previously between the amnion and chorion. If this is documented, then diminished activity with observation is a reasonable course. After 48 hours, if no additional amnionic fluid has escaped and if there is no bleeding, cramping, or fever, then a woman may resume ambulation and pelvic rest. With bleeding, cramping, or fever, abortion is considered inevitable, and the uterus is evacuated.
Bleeding that follows partial or complete placental separation and dilation of the cervical os is termed incomplete abortion. The fetus and the placenta may remain entirely within the uterus or partially extrude through the dilated os. Before 10 weeks, they are frequently expelled together, but later, they deliver separately. Management options of incomplete abortion include curettage, medical abortion, or expectant management in clinically stable women as discussed on Management of Spontaneous Abortion. With surgical therapy, additional cervical dilatation may be necessary before suction curettage. In others, retained placental tissue simply lies loosely within the cervical canal and can be easily extracted with ring forceps.
At times, expulsion of the entire pregnancy may be completed before a woman presents to the hospital. A history of heavy bleeding, cramping, and passage of tissue or a fetus is common. Importantly, during examination, the cervical os is closed. Patients are encouraged to bring in passed tissue, which may be a complete gestation, blood clots, or a decidual cast. The last is a layer of endometrium in the shape of the uterine cavity that when sloughed can appear as a collapsed sac (Fig. 19-3, Clinical Manifestations).
If an expelled complete gestational sac is not identified, sonography is performed to differentiate a complete abortion from threatened abortion or ectopic pregnancy. Characteristic findings of a complete abortion include a minimally thickened endometrium without a gestational sac. However, this does not guarantee a recent uterine pregnancy. Condous and associates (2005) described 152 women with heavy bleeding, an empty uterus with endometrial thickness < 15 mm, and a diagnosis of completed miscarriage. Six percent were subsequently proven to have an ectopic pregnancy. Thus, unless products of conception are seen or unless sonography confidently documents, at first an intrauterine pregnancy, and then later an empty cavity, a complete abortion cannot be surely diagnosed. In unclear settings, serial serum hCG measurements aid clarification. With complete abortion, these levels drop quickly (Connolly, 2013).
Also termed early pregnancy failure or loss, missed abortion, as originally defined, is contemporaneously misused compared with its meaning many decades ago. Historically, the term was used to describe dead products of conception that were retained for days, weeks, or even months in the uterus with a closed cervical os. Early pregnancy appeared to be normal with amenorrhea, nausea and vomiting, breast changes, and uterine growth. Because suspected fetal death could not be confirmed, expectant management was the sole option, and spontaneous miscarriage would eventually ensue. And because the time of fetal death could not be determined clinically, pregnancy-duration—and thus fetal age—was erroneously calculated from the last menses. To elucidate these disparities, Streeter (1930) studied aborted fetuses and reported that the mean death-to-abortion interval was approximately 6 weeks.
This historical description of missed abortion is in contrast to that defined currently based on results of serial serum β-hCG assays and transvaginal sonography (Fig. 18-4). With rapid confirmation of fetal or embryonic death, many women choose uterine evacuation. Although many classify these as a missed abortion, the term is used interchangeably with early pregnancy loss or wastage (Silver, 2011).
Transvaginal sonogram displays a large anechoic sac consistent with an anembryonic gestation. Calipers measure uterine length and anteroposterior thickness in a sagittal plane.
Horrific infections and maternal deaths associated with criminal septic abortions have become rare with legalized abortion. Still, perhaps 1 to 2 percent of women with threatened or incomplete miscarriage develop a pelvic infection and sepsis syndrome. Elective abortion, either surgical or medical, is also occasionally complicated by severe and even fatal infections (Barrett, 2002; Ho, 2009). Bacteria gain uterine entry and colonize dead conception products. Organisms may invade myometrial tissues and extend to cause parametritis, peritonitis, septicemia, and, rarely, endocarditis (Vartian, 1991). Particularly worrisome are severe necrotizing infections and toxic shock syndrome caused by group A streptococcus—S pyogenes (Daif, 2009).
During the last few years, rare but severe infections with otherwise low-virulence organisms have complicated medical abortions. Deaths have been reported from toxic shock syndrome due to Clostridium perfringens (Centers for Disease Control and Prevention, 2005). Similar infections are caused by Clostridium sordellii and have clinical manifestations that begin within a few days after an abortion. Women may be afebrile when first seen with severe endothelial injury, capillary leakage, hemoconcentration, hypotension, and a profound leukocytosis (Cohen, 2007; Fischer, 2005; Ho, 2009). Maternal deaths from these clostridial species approximate 0.58 per 100,000 medical abortions (Meites, 2010).
Management of clinical infection includes prompt administration of broad-spectrum antibiotics as discussed in Chapter 37 (Perioperative Prophylaxis). If there are retained products or fragments, then suction curettage is also performed. Most women respond to this treatment within 1 to 2 days, and they are discharged when afebrile. Follow-up oral antibiotic treatment is likely unnecessary (Savaris, 2011). In a very few women, severe sepsis syndrome causes acute respiratory distress syndrome, acute kidney injury, or disseminated intravascular coagulopathy. In these cases, intensive supportive care is essential (Chap. 47, Obstetrical Intensive Care).
To prevent postabortal sepsis, prophylactic antibiotics are given at the time of induced abortion or spontaneous abortion that requires medical or surgical intervention. The American College of Obstetricians and Gynecologists (2011b) recommends doxycycline, 100 mg orally 1 hr before and then 200 mg orally after a surgical evacuation. At Planned Parenthood clinics, for medical abortion, doxycycline 100 mg is taken orally daily for 7 days and begins with abortifacient administration (Fjerstad, 2009b).
Management of Spontaneous Abortion
With embryofetal death now easy to verify with current sonographic technology, management can be more individualized. Unless there is serious bleeding or infection with an incomplete abortion, any of three options are reasonable—expectant, medical, or surgical management. Each has its own risks and benefits—for example, the first two are associated with unpredictable bleeding, and some women will undergo unscheduled curettage. Also, success of any method depends on whether the woman has an incomplete or missed abortion. Some of the risks and benefits are summarized as follows:
Expectant management of spontaneous incomplete abortion has failure rates as high as 50 percent.
Medical therapy with prostaglandin E1 (PGE1) has varying failure rates of 5 to 40 percent. In 1100 women with suspected first-trimester abortion, 81 percent had a spontaneous resolution (Luise, 2002).
Curettage usually results in a quick resolution that is 95- to 100-percent successful. It is invasive and not necessary for all women.
It is possible that patients and clinicians opt for surgical methods when there is not a strict protocol for medical treatment (Kollitz, 2011).
Several randomized studies that compared these management schemes were reviewed by Neilson (2010). A major drawback cited for between-study comparisons was varied inclusion criteria and techniques. For example, studies that included women with vaginal bleeding reported greater success for medical therapy than did studies that excluded such women (Creinin, 2006). With these caveats in mind, selected studies reported since 2005 are listed in Table 18-3. Importantly, Smith and coworkers (2009) reported that subsequent pregnancy rates did not differ among these management methods.
Table 18-3Randomized Controlled Studies for Management of Various Types of First-Trimester Pregnancy Loss ||Download (.pdf) Table 18-3 Randomized Controlled Studies for Management of Various Types of First-Trimester Pregnancy Loss
|Study ||Inclusion Criteria ||No. ||Treatment Arms ||Outcomes |
|Nguyen (2005) ||Incomplete SAB ||149 ||(1) PGE1, 600 μg orally ||60% completed at 3 d |
| || || ||(2) PGE1, 600 μg orally initially and at 4 hr ||95% at 7 d; 3% curettage |
|Zhang (2005) ||Pregnancy failureb ||652 ||(1) PGE1, 800 μg vaginally ||71% completed at 3 d; 16% failure |
| || || ||(2) Vacuum aspiration ||97% successful |
|Trinder (2006) (MIST Trial) ||Incomplete SAB; missed AB ||1200 ||(1) Expectant ||50% curettage |
| || || ||(2) PGE1, 800 μg vaginally + 200 mg mifepristone ||38% curettage |
| || || ||(3) Suction curettage ||5% repeat curettage |
|Dao (2007) ||Incomplete SAB ||447 ||(1) PGE1, 600 μg orally ||95% completed |
| || || ||(2) Vacuum aspiration ||100% curettage |
|Torre (2012) ||First-trimester miscarriageb ||174 ||(1) Immediate—PGE1, 200 μg orally now; 400 μg vaginally day 2 ||81% completed |
| || || ||(2) Delayed—no Rx; TVS days 7 and 14 ||57% completed |