Urea and dilatation of the cervix

Forces required for dilatation of human cervix in first trimester of pregnancy

Cervical resistance to dilatation was measured in 76 patients undergoing first trimester legal abortion; a specially designed force-sensing instrument was used. No correlation between cervical resistance and patient age or gestational age was found. Increasing parity and earlier legal abortions were significantly correlated with a lowering of the cervical resistance. In patients dilated to 11 mm a lowering of resistance was noted suggesting a tear in cervical tissue.

Low-dose prostaglandin E2 analogue for cervical dilatation prior to pregnancy termination

The trauma of mechanical cervical dilatation preceding abortion is directly related to the degree of cervical resistance. Prostaglandins may reduce cervical rigidity but are accompanied by undesirable side effects. Our aims were to ascertain if a low-dose (10 mg) analogue (9-deoxo-16, 16 dimethyl-9-methylene PGE2) is effective and well tolerated and, if so, to try to determine the possible mechanism by which it works. To this end, we studied 39 women with gestational ages ranging from 7 to 19 weeks who were given a single vaginal suppository 1 to 4 hours before suction curettage. In addition to demographic data on age, gravidity, parity, and previous abortions, we determined progesterone, human chorionic gonadotropin and prostaglandin plasma levels. This low-dose prostaglandin E2 analogue was found to be effective in achieving cervical dilatation and softening with minimal side effects (mild nausea in one patient only). Mean cervical dilatation achieved was 7.8 +/- 2.3 mm. Softening was apparent and facilitated additional instrumental dilatation when required. No correlation was found between drug effectiveness and gravidity, gestational age, or duration of action. There was no detectable trend with regard to baseline progesterone or human chorionic gonadotropin levels. This suggested a specific sensitivity to the local effect by the drug, apparently unrelated to dosage.

Properties and safety of cervical dilators

Characteristics of cervical dilation produced by the new osmotic dilator, laminaria, and rigid (metal or plastic) dilators were compared. The osmotic dilator (Lamicel) is an open-porosity polyvinyl alcohol sponge loaded with magnesium sulfate and compressed into a rod. Pressures exerted by the Lamicel and laminaria tents were measured by placing them in a short elastic collar to simulate the cervical canal and allowing them to swell in water. At maximum dilation of the collar, the laminaria exerted 190 kPa (kPa = kilopascals; 6.895 kPa = 1 pound force/square inch), and the osmotic dilator, 14 kPa. The pressure that may be applied to the cervical canal with rigid dilators may be as much as 700 kPa. Because the Lamicel dilates the cervix passively and is as effective as laminaria, it appears to be the safest method of cervical dilation.