Cervical stroma apoptosis in pregnancy.

Objective: To determine whether the percentage of apoptotic nuclei is different in cervical stroma of pregnant laboring women compared with nonpregnant women and pregnant nonlaboring women.

Methods: We took cervical stromal biopsies during cesarean delivery at the level of the lower uterine segment from ten women in active labor and 13 women before labor. In addition, we took biopsies of cervical stroma at the level of the internal cervical os from hysterectomy specimens in ten reproductive-aged women. Cryosections were then analyzed using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining. Tissue specimens were analyzed with ligation-mediated polymerase chain reaction to visualize nucleosomal ladders characteristic of apoptosis. To detect a 10% difference in the percentage of apoptotic cells per subject between study groups assuming a power of 0.90, an alpha of.05 in approximately ten subjects per group was needed.

Results: The median percentage of apoptotic nuclei was 0.7 (interquartile range 0.4, 1.4) for the nonpregnant group, 7.5 (interquartile range 6.6, 11.2) for the pregnant nonlaboring group, and 11.6 (interquartile range 8.3, 16.7) for the pregnant laboring group (P <.001). The percentage of apoptotic nuclei differed significantly across the three study groups. Using ligation-mediated polymerase chain reaction, nucleosomal ladders were seen in the specimens from pregnant women but not in the specimens from nonpregnant women, confirming the increase in stromal apoptosis seen with pregnancy.

Conclusion: Apoptosis of cervical stromal cells may play a role in the remodeling of the cervix during pregnancy and contribute to cervical changes during labor.