Methods of Induced Abortion

Numerous methods are used to induce an abortion: suction or surgical curettage; induction of labor by means of intra- or extraovular injection of a hypertonic solution or other oxytocic agent; dilatation and evacuation; extraovular placement of devices such as catheters, bougies, or bags; hysterotomy - abdominal or vaginal; hysterectomy - abdominal or vaginal; and menstrual regulation.

The method of abortion used is determined primarily by the duration of pregnancy, with consideration for the patient’s health, the experience of the physician, and the available physical facilities.

Suction curettage on an outpatient basis under local or light general anesthesia can be accomplished with a high degree of safety. The safety of outpatient abortion and the shortage of hospital beds have led to the development of single-function, “free-standing” abortion clinics. In addition to providing more efficient counseling and social services, these clinics have effectively reduced the cost of abortion. Many hospitals have “short-stay units,” that match the efficiency of the outpatient clinics but also offer the back-up facilities of the general hospital.

A. Suction Curettage

Suction curettage is the safest and most effective method to terminate pregnancies of 12 weeks’ duration or less. This technique has gained rapid worldwide acceptance, and over 90% of induced abortions in the U.S. are now performed by this method. The procedure involves dilatation of the cervix by instruments or by hydrophilic Laminaria tent (see following text), followed by the insertion of a suction cannula of the appropriate diameter into the uterine cavity (

Fig 33-5). Standard negative pressures used are in the range of 30-50 mm Hg. Many physicians follow aspiration with light instrumental curettage of the uterine cavity.

The advantages of suction over surgical curettage are that the former empties the uterus more rapidly, minimizes blood loss, and reduces the likelihood of perforation of the uterus. However, failure to recognize perforation of the uterus with a cannula may result in serious damage to other organs. Knowledge of the size and position of the uterus and the volume of the contents is mandatory for safe suction curettage. Moreover, extreme care and slow minimal dilatation of the cervix, with special consideration for the integrity of the internal os, should prevent injury to the cervix or uterus. Attention to the decrease in uterine size that occurs with rapid evacuation helps to avoid uterine injury.

When performed in early pregnancy by properly trained physicians, suction curettage should be associated with a very low failure rate; the complication rate should be under 1% for infection, about 2% for excessive bleeding, and under 1% for uterine perforation. The risk of major complications such as persistent fever, hemorrhage requiring transfusion, and unintended major surgery ranges between 0.2% and 0.6% and is proportional to pregnancy duration. The incidence of mortality for suction curettage is about 1 in 100,000 patients.

B. Surgical Curettage

Surgical (“sharp”) curettage has been used for first-trimester abortion in the absence of suction curettage equipment. This procedure is performed as a standard D&C, such as for the diagnosis of abnormal uterine bleeding or for the removal of endometrial polyps. The blood loss, duration of surgery, and likelihood of damage to the cervix or uterus are greatly increased when surgical curettage is used. In addition, the risk of uterine synechiae or Asherman’s syndrome is also increased with this approach. Accordingly, suction curettage is generally preferred over sharp curettage for carrying out first-trimester termination procedures.

C. Medical Abortion with Methotrexate and Misoprostol

Women with first trimester pregnancies less than 49 days from their first day of the last menstrual period may be eligible for medical abortion. The protocol consists of intramuscular methotrexate (50 mg/m2) given on day 1 and then misoprostol (prostaglandin E1) 800 ug inserted vaginally on day 5, 6, or 7. Suction curettage may be required if the pregnancy appears viable 2 weeks after methotrexate, if a gestational sac persists 4 weeks after methotrexate, or at any time for excessive bleeding. In a study of 659 women, only 13% required a suction curettage.

D. Induction of Labor by Intra-Amniotic Instillation

The Japanese developed this technique for induced abortion after the first trimester. Currently, it is used almost exclusively for initiating midtrimester abortion. The original procedure was to perform amniocentesis, aspirate as much fluid as possible, and then instill into the amniotic sac 200 mL of hypertonic (20%) sodium chloride solution. In most (80-90%) cases, spontaneous labor and expulsion of the fetus and placenta would occur within 48 hours. Modifications of this technique have developed, primarily to reduce the injection-abortion interval, and as a result of the development of other agents that initiate labor when instilled intra-amniotically.

Because of the problems associated with hypertonic sodium chloride, many clinicians have used intra-amniotic hyperosmolar (59.7%) urea, usually with oxytocin or prostaglandin or intra-amniotic prostaglandin alone. These approaches result in injection-abortion intervals of 16-17 hours for urea and 19-22 hours for prostaglandin. The urea is instilled in a fashion similar to that described for hypertonic sodium chloride; the prostaglandin, most frequently PGF, is usually instilled as a single dose of 40-50 mg or as 2 doses of 25 mg instilled 6 hours apart. When using oxytocin to augment these agents, note that because of the relative insensitivity of the myometrium to oxytocin at this stage of pregnancy, doses as high as 332 mU/min are required to produce uterine contractions. To avoid water intoxication, the oxytocin is made up in highly concentrated solutions and given at slow rates.

It is advantageous to soften the unripe cervix with Laminaria tents placed in the cervix a few hours before amniocentesis is performed. Such an approach markedly reduces the risk of cervical injury.

Midtrimester induced abortion by this method must be done with scrupulous aseptic surgical technique, and the patient must be monitored until the fetus and placenta are delivered and postabortion bleeding is under control. The complication rate is high - up to 20% in some institutions - and the mortality rate is comparable to that of term parturition. Fortunately, because first-trimester abortion is now more readily available, more women are consulting their physicians early and thus availing themselves of the much safer suction curettage.

Several types of complications are associated with the use of instillation agents. Retained placenta is the most common problem; rates ranging from 13-46% have been reported. The placenta can usually be removed with ring forceps and large curets without difficulty with the patient under local anesthesia. Hemorrhage may be caused by retained products or atony; coagulopathy is seen in up to 1% of patients in whom hypertonic sodium chloride is used. Infection can also be encountered, but is reduced significantly by the use of prophylactic antibiotics in high-risk situations, eg, in patients with early ruptured membranes and during injection-abortion intervals greater than 24 hours. Cervical laceration can also occur; a complication that is reduced by the use of Laminaria tents. Hypernatremia can occur with the use of hypertonic sodium chloride if the drug is absorbed rapidly by the placental bed or if it is given intravascularly by mistake.

Failure of labor to expel the products of conception necessitates either a repetition of the procedure if the membranes are still intact or oxytocin stimulation, usually by intravenous injection or use of the dilatation and evacuation technique.

Emotional stress is an important factor for many women, since they are awake at the time of the expulsion of the fetus and the fetus is well formed. (The emotional stress is also a factor for hospital personnel - a problem impossible to avoid.)

E. Induction of Labor with Vaginal Prostaglandins

Prostaglandin E2 given intravaginally can also be used to induce midtrimester abortion. Vaginal suppositories containing 20 mg are used every 3-4 hours until abortion occurs; the presence or absence of labor determines whether to stop the prostaglandin E2. Misoprostol, a synthetic prostaglandin E1 analog is also utilized. Treatment-abortion intervals, rates of incomplete abortion, and complications are similar to those described for instillation agents. The major disadvantages are significant gastrointestinal side effects, a higher incidence of live abortion, and a more frequent occurrence of fever.

F. Dilatation and Evacuation

This technique for inducing midtrimester abortion is essentially a modification of suction curettage. Because fetal parts are larger at this stage of pregnancy, serial placement of Laminaria tents is used by most operators to effect cervical dilatation with less likelihood of injury. Larger suction cannulas and specially designed forceps are used to extract tissue. In most instances, the operation can be performed in the outpatient setting using paracervical block anesthesia and intravenous sedation on patients with pregnancies of up to 18 weeks’ gestation. Complications include hemorrhage (usually due to atony or laceration), perforation, and rarely infection. Retained tissue is uncommon, especially when careful inspection of tissue for completion is carried out at the end of each procedure. Compared with instillation techniques or vaginal prostaglandin, the overall incidence of complications (in pregnancies up to 18 weeks’ gestation) is less with dilatation and evacuation. In addition, the technique is preferred by most patients because it is an outpatient procedure and the woman does not undergo labor.

G. Hysterotomy and Hysterectomy

The use of hysterotomy and hysterectomy is currently reserved for special circumstances such as in failure to complete a midtrimester abortion due to cervical stenosis or in the management of other complications. Both approaches, compared with other techniques discussed, have unacceptably high rates of morbidity and mortality and neither should be used as a primary method.

H. Menstrual Regulation

Menstrual regulation consists of aspiration of the endometrium within 14 days after a missed menstrual cycle or within 42 days after the beginning of the last menstrual period by means of a small cannula attached to a source of low-pressure suction such as a syringe or other suction machine. This is a simple and safe procedure that can be readily performed in the office or outpatient clinic, usually without any anesthetic, although paracervical block can be used if necessary. Menstrual regulation was used extensively in the 1970s and 1980s before reliable, inexpensive, and sensitive urine pregnancy tests were available. It offered a safe early approach to pregnancy termination; however, about 40% of women were not pregnant at the time of the procedure. With the advent of urine pregnancy tests that have the ability to document pregnancy even before a missed menstrual period, standard first-trimester suction curettage is probably more widely used. Complications are similar to those described for suction curettage except that persistent pregnancy is more common, particularly when very early menstrual regulation procedures are performed.

I. RU-486

RU-486 (mifepristone) is a synthetic drug developed by French pharmacologists, which acts at least partially as an antiprogestational agent. When given orally in conjunction with a prostaglandin such as misoprostol, it effects first-trimester abortion. Complications include failure to terminate a pregnancy, incomplete abortion, and significant uterine cramping.

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Provided by ArmMed Media
Revision date: July 5, 2011
Last revised: by Jorge P. Ribeiro, MD