Induced abortion is legally available to about two thirds of women worldwide. In the US, abortion is legal during the 1st trimester (≤ 12 wk); after that, legality varies by state. In the US, about half of pregnancies are unintended; about 40% of these are terminated by elective abortion, with 90% during the 1st trimester.

Common methods of inducing abortion are instrumental evacuation through the vagina and medical induction (stimulation of uterine contractions). Uterine surgery (hysterotomy or hysterectomy) is a last resort, which is usually avoided because mortality rates are higher. Hysterotomy also results in a uterine scar, which may rupture in subsequent pregnancies.

Typically, gestational age, which usually dictates abortion method, is established by ultrasonography. Rh₀(D) immune globulin, when indicated, is given to women with Rh-negative blood to prevent sensitization. First-trimester abortions often require only local anesthesia; later abortions sometimes require general anesthesia.

Instrumental evacuation

Instrumental evacuation is used in 97% of all abortions.

At 4 to 6 wk, the uterus can be curetted gently via a cannula attached to a vacuum source. Because failure to terminate the pregnancy is more common in early than in later weeks, instrumental evacuation should usually not be done until a gestational sac is seen. Before this time, abortion is usually induced medically.

At 7 to 12 wk, dilation and curettage (D & C) is usually used; large-diameter suction cannulas are usually required, so the cervix must be dilated. Typically, progressively increasing sizes of tapered dilators are used. Cervical damage due to dilation can be prevented or minimized by using laminaria (dried seaweed stems) or other osmotic dilators, which can be inserted into the cervix and left for ≥ 4 h (usually overnight). They dilate the cervix by expanding or stimulating prostaglandin release.

At 12 to 18 wk, dilation and evacuation (D & E) is usually used. The cervix is dilated, usually with laminaria or other osmotic dilators and dilating instruments. Forceps are used to dismember and remove the fetus, and a suction cannula is used to aspirate the amniotic fluid, placenta, and fetal debris. D & E requires more skill than do other methods of instrumental evacuation.

Medical induction

Medical induction can be done for pregnancies of < 7 to 9 wk or > 15 wk.

For pregnancies of up to 9 wk, mifepristone (RU 486) 200 to 600 mg po, a progesterone-receptor blocker, followed by misoprostol 400 μg po or 800 μg intravaginally, is about 95% effective in terminating pregnancies.

After 15 wk, prostaglandins are used. They include vaginal prostaglandin E₂ (dinoprostone) suppositories, intravaginal prostaglandin E₁ analog (misoprostol) tablets, and IM injections of prostaglandin F_2α (dinoprost tromethamine). Using two 200-μg intravaginal tablets of misoprostol q 6 h is nearly 100% successful within 48 h of treatment.

Adverse effects of prostaglandins include nausea, vomiting, diarrhea, hyperthermia, facial flushing, vasovagal symptoms, bronchospasm, and decreased seizure threshold. In women with a severe kidney or liver disorder, activation of the prostaglandin may be decreased, so dose should be increased.

Complications

Complication rates with abortion (serious complications in < 1%; mortality in < 1 in 100,000) are higher than those with contraception, although the rates have decreased in the last few decades. Complication rates increase as gestational age increases.

Serious early complications include perforation of the uterus (0.1%) or, less often, of the intestine or another organ by an instrument. Major hemorrhage (0.06%) may result from trauma or an atonic uterus. Laceration of the cervix (0.1 to 1%) ranges from superficial tenaculum tears to cervicovaginal tears, rarely with fistulas. General or local anesthesia rarely causes serious complications.

The most common delayed complications include bleeding and significant infection (0.1 to 2%), which usually occur simultaneously because placental fragments are retained, and thrombophlebitis. If bleeding occurs or infection is suspected, pelvic ultrasonography is done; retained placental fragments may be visible on ultrasound scans. Mild inflammation is expected, but if infection is moderate or severe, peritonitis or sepsis may occur. Sterility may result from synechiae in the endometrial cavity or tubal fibrosis due to infection. Forceful dilation of the cervix in more advanced pregnancies may contribute to incompetent cervix. Elective abortion probably does not increase risks for the fetus or woman during subsequent pregnancies.

Psychologic complications do not typically occur but may occur in women who had psychologic symptoms before pregnancy, who terminated a desired pregnancy for medical reasons (maternal or fetal), who have considerable ambivalence about the abortion, who are adolescents, who had a late abortion, or who obtained an abortion illegally.

Last full review/revision August 2007 by Daniel R. Mishell, Jr., MD; Megan A. Economidis, MD