SECOND-TRIMESTER ABORTION

Most abortions are performed before 13 menstrual weeks. Later abortions are generally performed because of fetal defects, maternal illness, or maternal age. Younger women are much more likely to request abortion after 12 weeks.

Dilation and Evacuation

Transcervical instrumental evacuation of the uterus (D&E) is the method most commonly used in the United States for mid-trimester abortions before 21 menstrual weeks. Two D&E techniques are used and differ primarily in the preparatory steps that precede the evacuation. In the one-stage technique, forcible dilation is performed slowly and carefully to sufficient diameter to allow insertion of large, strong ovum forceps for evacuation. The better approach is a two-stage procedure in which multiple laminaria are used to achieve gradual dilatation over several hours before extraction.

Overnight placement of one set of laminaria is sufficient preparation for the early mid-trimester, but beyond 18-20 weeks, two sets of laminaria and 2 days of preparation are often used. Oral tetracycline or doxycycline should be started after laminaria insertion and continued for 2 days after uterine evacuation. Uterine evacuation is accomplished with long, heavy forceps, using the vacuum cannula to rupture the fetal membranes, drain amniotic fluid, and ensure complete evacuation. A large-bore, 16-mm vacuum system facilitates the procedure. The procedure causes discomfort despite a paracervical block, and most patients will benefit from conscious seda-tion.

If general anesthesia is elected, potent inhalation agents should be avoided or used only in low concentrations to avoid uterine atony and increased blood loss. Standard care of the anesthetized patient must be provided, with continuous monitoring of tissue oxygenation and end-expiratory carbon dioxide and frequent monitoring of vital signs.

The patient must be closely supervised until she is fully recovered from anesthesia.

Preoperative ultrasonography is necessary for all cases 14 weeks and beyond. Intraoperative real-time
ultrasonography helps to locate fetal parts within the uterus. Paracervically administered vasopressin has been demon-strated to significantly reduce bleeding, but vasopressin must be used with caution. A maximum of 4 units should be used, and it is usually diluted with saline or Xylocaine. Vasopressin should not be used in women with heart disease or hypertension. Intravenous oxytocin is begun early in the procedure, just after rupture of the membranes.

Coagulopathy can be seen after D&E, apparently because tissue thromboplastins have been released into the maternal venous sinusoids. The use of oxytocin and intracervical vasopressin may reduce this risk. To avoid negative pressure in the uterine vasculature, the Trendelenburg position should not be used.

After the procedure, the operator must examine the fetal parts carefully to be sure that evacuation is complete. If the fetal calvarium has been retained in the uterus and gentle attempts at extraction fail, the procedure should be completed under ultrasound guidance. If this is not available, it is best to stop, administer an oxytocin infusion for 2 hours, and try again. By then, the remaining fetal parts usually will have been pushed down to the internal cervical os and they can be extracted easily.

Dilation and evacuation becomes progressively more difficult as gestational age advances, and in the United States instillation techniques are often used after 21 weeks. Dilation and evacuation can be offered in the late mid-trimester, but the technique should be modified. The use of two sets of laminaria tents for a total of 36-48 hours is favored. A further modification is the Hern combination method. After multistage laminaria treatment, urea is injected into the amniotic sac. Extraction is then accomplished after labor begins and after fetal maceration has occurred.

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