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Induced Abortion

(Interruption of Pregnancy)

By

Frances E. Casey

, MD, MPH, Virginia Commonwealth University Medical Center

Last full review/revision May 2020| Content last modified May 2020
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In the US, abortion of a previable fetus is legal, although state-specific restrictions (eg, mandatory waiting periods, gestational age restrictions) exist. In the US, about half of pregnancies are unintended. About 40% of unintended pregnancies end in induced abortion; 90% of procedures are done during the 1st trimester.

In countries where abortion is legal, abortion is usually safe and complications are rare. Worldwide, 13% of maternal deaths are secondary to induced abortion, and the overwhelming majority of these deaths occur in countries where abortion is illegal.

Pregnancy should be confirmed before abortion is induced. Often, gestational age is established by ultrasonography, but sometimes history and physical examination can accurately confirm gestational age during the 1st trimester. Doppler ultrasonography should be considered if a woman is in the 2nd trimester and has placenta previa or an anterior placenta plus a history of a uterine scar.

Completion of an induced abortion can be confirmed by directly observing removal of uterine contents or via ultrasonography used during the procedure. If ultrasonography is not used during the procedure, resolution of the pregnancy can be confirmed by measuring quantitative serum beta–human chorionic gonadotropin (beta-hCG) levels before and after the procedure; a decrease of > 50% after 1 week confirms resolution.

Antibiotics effective against reproductive tract organisms (including chlamydiae) should be given to the patient on the day of the abortion. Traditionally, doxycycline is used; 200 mg is given before the procedure. After the procedure, Rho(D) immune globulin is given to women with Rh-negative blood.

First-trimester abortions often require only local anesthesia, but trained clinicians may offer sedation in addition. For later abortions, deeper sedation is usually required.

Contraception (all forms) can be started immediately after an induced abortion at < 28 weeks gestation.

Methods

Common methods of inducing abortion are

  • Instrumental evacuation of the uterus after cervical dilation

  • Medical induction (drugs to stimulate uterine contractions)

The method used depends in part on the length of the pregnancy. Instrumental evacuation can be used for most pregnancies. Drugs can be used for some pregnancies that are < 11 weeks or > 15 weeks.

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.

Instrumental evacuation

Typically at < 14 weeks, dilation and curettage (D & C) is used, usually with a large-diameter suction cannula, inserted into the uterus.

At < 9 weeks, manual vacuum aspiration (MVA) can be used. It produces enough pressure to evacuate the uterus. MVA devices are portable, do not require an electrical source, and are quieter than electrical vacuum aspiration (EVA) devices. MVA may also be used to manage spontaneous abortion during early pregnancy. After 9 weeks, EVA is used; it involves attaching a cannula to an electrical vacuum source.

At 14 to 24 weeks, dilation and evacuation (D & E) is usually used. 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 and requires more training than do other methods of instrumental evacuation.

Often, progressively increasing sizes of tapered dilators are used to dilate the cervix before the procedure. However, depending on gestational age and parity, clinicians may need to use another type of dilator instead of or in addition to tapered dilators to minimize the cervical damage that tapered dilators can cause. Choices include

  • The prostaglandin E1 analog (misoprostol)

  • Osmotic dilators such as laminaria (dried seaweed stems)

Misoprostol dilates the cervix by stimulating prostaglandin release. Misoprostol is usually given vaginally or buccally 2 to 4 hours before the procedure.

Osmotic dilators can be inserted into the cervix and left for ≥ 4 hours (often overnight if the pregnancy is >18 weeks). Osmotic dilators are usually used at > 16 to 18 weeks.

Medical induction

Medical induction can be used for pregnancies of < 11 weeks or > 15 weeks. If patients have severe anemia, medical induction should be done only in a hospital so that blood transfusion is readily available.

In the US, medical abortion accounts for 25% of abortions done at < 10 weeks.

For pregnancies of < 10 weeks, regimens include the progesterone-receptor blocker mifepristone (RU 486) and the prostaglandin E1 analog misoprostol, as follows:

  • Mifepristone 200 mg orally, followed by misoprostol 800 mcg buccally at 24 to 48 hours (for pregnancies of 10 to 11 weeks, an additional dose of misoprostol 800 mcg buccally is taken 4 hours after the initial misoprostol dose)

Misoprostol may be taken by the patient or given by a clinician.

This regimen is about 95% effective in pregnancies of 8 to 9 weeks and 92% effective in pregnancies of > 9 to 10 weeks (1).

A follow-up visit is required to confirm resolution of the pregnancy and, if necessary, to provide contraception.

After 15 weeks, pretreatment with mifepristone 200 mg 24 to 48 hours before induction reduces induction times. Prostaglandins are used to induce abortion. Options include

  • Vaginal prostaglandin E2 (dinoprostone) suppositories

  • Vaginal and buccal misoprostol tablets

  • IM injections of prostaglandin F2-alpha (dinoprost tromethamine)

The typical dose of misoprostol is 600 to 800 mcg vaginally, followed by 400 mcg buccally every 3 hours for up to 5 doses. Or, two 200-mcg vaginal tablets of misoprostol every 6 hours can be used; abortion occurs within 48 hours in almost 100% of cases.

Adverse effects of prostaglandins include nausea, vomiting, diarrhea, hyperthermia, facial flushing, vasovagal symptoms, bronchospasm, and decreased seizure threshold.

Methods reference

Complications

Complication rates with safe, legal abortion (serious complications in < 1%; mortality in < 1 in 100,000) are higher than those with contraception; however, rates are 14 times lower than those after delivery of a full-term infant, and 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%), which may result from trauma or an atonic uterus

  • Laceration of the cervix (0.1 to 1%), which are typically superficial tenaculum tears but can be more serious and require repair

General or local anesthesia rarely causes serious complications.

The most common delayed complications include

  • Bleeding and significant infection (0.1 to 2%)

These complications usually occur because placental fragments are retained. If bleeding occurs or infection is suspected, pelvic ultrasonography is done; retained placental fragments may be visible on an ultrasound scan. 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 (Asherman syndrome) or tubal fibrosis due to infection. Forceful dilation of the cervix in more advanced pregnancies may contribute to incompetent cervix. However, induced 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

  • Had significant emotional attachment to the pregnancy

  • Have limited social support or feel stigmatized by their support system

Key Points

  • About 40% of unintended pregnancies end in induced abortion.

  • Common methods for abortion are instrumental evacuation of the uterus after cervical dilation or medical induction (to induce uterine contractions).

  • Before doing an abortion, confirm that the woman is pregnant, and if so, determine gestational age based on history and physical examination and/or ultrasonography.

  • For instrumental evacuation, usually use D & C at < 14 weeks gestation and D & E at 14 to 24 weeks, sometimes preceded by cervical dilation using misoprostol or osmotic dilators (eg, laminaria).

  • For medical induction, give mifepristone, followed by misoprostol at < 11 weeks gestation; after 15 weeks gestation, pretreat with mifepristone, then give a prostaglandin (eg, dinoprostone vaginally, misoprostol vaginally and buccally, prostaglandin F2-alpha IM, or misoprostol vaginally).

  • Serious complications (eg, uterine perforation, major bleeding, serious infection) occur in < 1% of abortions.

  • Induced abortion probably does not increase risks in subsequent pregnancies.

Drugs Mentioned In This Article

Drug Name Select Trade
Gammagard S/D
THAM
CRINONE
CERVIDIL, PREPIDIL, PROSTIN E2
MIFEPREX
CYTOTEC
PERIOSTAT, VIBRAMYCIN
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