A novel optical method to assess cervical changes during pregnancy and use to evaluate the effects of progestins on term and preterm labor

Abstract

Objective: The purpose of this study was to determine whether optical methods can estimate cervix function during pregnancy and whether progestins modify this process.

Study design: Photos of the external cervix of timed-pregnant rats were taken every other day from day 13 until postpartum day 5 after daily treatments with vehicle (controls) or progestin treatments (progesterone, subcutaneously or vaginally; 17-alpha-hydroxyprogesterone caproate [17P] and RU-486 subcutaneously, once on day 16). The surface area of the cervix was estimated from photos.

Results: The surface area of cervix increases throughout pregnancy and reverses after delivery in controls. In the progesterone subcutaneously or 17P subcutaneously groups, increases in surface area are lower (17P group until day 19 only; P < .05). Vaginal progesterone does not prevent surface area increases. Only the progesterone subcutaneously blocked delivery. RU-486 increases the surface area of the cervix (P < .05) during preterm delivery.

Conclusion: An optical method is useful for quantitative assessment of the cervix and evaluation of agents that modify cervical function.

Figure 1

Photos of the external cervix throughout pregnancy (D13 = day 13 of gestation to D21) and postpartum (day 5 postpartum).

Figure 2

Figure 2A: Figure showing surface area of cervix (means ± SD of the surface area of the cervix) obtained in vivo from pregnant rats (N = 6) at different days of pregnancy and postpartum treated daily with vehicle (controls). Different letters indicate significant differences between mean values (P < .05). Figure 2B: Bar graphs showing means ± SD of cervical light-induced fluorescence (LIF) obtained in vivo from pregnant rats (N = 6) at different days of pregnancy and postpartum treated daily with vehicle (controls). Significant differences (P <0 .05) between groups are marked with different letters.

Figure 3

Figure showing surface area of cervix (means ± SD of the surface area of the cervix) obtained in vivo from pregnant rats (N = 6/ group) at different days of pregnancy and postpartum treated with various progestins or vehicle. Figure 3A: Daily treatment with vehicle (controls) or P4 (4 mg, s.c.). Note that delivery is inhibited in the treatment group. Figure 3B: Daily treatment with vehicle (controls) or 17P (10 mg, s.c.). Note that significant differences are only observed until day 19 of gestation. Figure 3C: Twice a day treatment with vehicle (controls) or vaginal P4 (15 mg bid). Note that no significant differences are observed at any time between controls vs. treated animals. Figure 3D: Treatment once on day 16 with vehicle (controls) or RU-486 (3 mg s.c.). Note that animals treated with RU-486 delivered prematurely. Asterisks indicate P < 0.05 compared with controls.

Figure 4

Shown is the percent of animals delivering versus day of pregnancy after various treatments: RU-486 (single treatment, 3mg s.c., on day 16,), daily treatments from day 13 until delivery for P4 (4 mg s.c. or 15 mg vaginal bid), 17P (10 mg s.c.) and controls (0.2 ml sesame oil (vehicle) s.c. or 0.18 ml vaginal gel bid). Note that injections of P4 completely blocked delivery, whereas 17P or vaginal P4 had no effect on delaying term delivery. RU- 486 induced preterm delivery.