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  • Title: Pharmacological modulation of cervical compliance in the first and second trimesters of pregnancy.
    Author: Calder AA, Greer IA.
    Journal: Semin Perinatol; 1991 Apr; 15(2):162-72. PubMed ID: 1876872.
    Abstract:
    Health practitioners use many methods and agents to bring on cervical ripening in early pregnancy, such as intracervical tents and pharmacological techniques, to induce a therapeutic abortion. Prostaglandins alter myometrial and cervical tissue and are the most often used pharmacological technique. Reduced collagen concentration, an increase in water volume, an increase in prostaglandins (PGE2, PGI2, and PGF2 alpha), and a change in the glycosaminoglycan (GAG) content coincide with cervical ripening, yet the mechanism responsible for these changes is obscure. Prostaglandins appear to cause the breakdown of collagen or change the GAG/proteoglycan content. Research shows that prostaglandins can initiate cervical ripening at any stage of pregnancy. Estradiol stimulates prostaglandin production thereby al so inducing cervical dilation. Relaxin also demonstrates an ability to ripen the cervix. In addition, mifepristone (RU-486) is gaining acceptance as a cervical ripening agent. In fact, RU-486 and gemeprost have at least 95% success rate compared to 92% for gemeprost alone or 85% with RU-486 alone. The only effective and acceptable prostaglandins to use at gestation of 0-8 weeks are sulprostone, gemeprost, and 9-methylene-PGE2. At t his gestational age, pharmacological modulation is all that is needed. Even though they are effective (abortion rate 90%), side effects are expected to occur (pain, nausea, and vomiting). Similarly, prostaglandin analogues are preferable for cervical ripening in women at 8-12 weeks gestation. Suction curettage or other surgical techniques then are used to remove the conceptus. At 12-16 weeks gestation, many physicians prefer the same protocol as that of 8-12 weeks gestation. Other choose to infuse PGE2 and saline into the amniotic fluid to stimulate uterine contractions. Another procedure at 12-16 weeks involves 1mg vaginal pessaries of gemeprost every 3 hours to ripen the cervix and stimulate contractions. After 16 weeks, the methods for 12-16 weeks still apply.
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