Clinical Findings in Amniotic Fluid of Women With Asymptomatic Short Cervix in the Midtrimester

Objective: To correlate amniotic fluid (AF) findings in women with asymptomatic short cervix in the midtrimester to pregnancy outcome.

Study Design: 30 women with an asymptomatic singleton pregnancy, and an incidental finding of transvaginal cervical length <15mm at 16-27 weeks gestation underwent amniocentesis. AF was analyzed for chemistry (glucose and LDH), cytology (WBC and total cell count), and microbiology (gram stain, aerobic, anaerobic, and mycoplasma cultures). Women were divided into a cerclage (WBC <= 5, negative cultures and gram stain) or vaginal progesterone (200 mg nightly) treatment arm depending on their AF findings. Pregnancy outcome data was collected and compared with initial AF findings.

Results: 5 women met criteria for cerclage and four underwent the procedure. The remaining 25 were treated with vaginal progesterone. AF fluid gram stain and cultures were negative for pathogens. Average gestational age (GA) at birth for the entire population was 31.9 weeks. When compared with the patients who had WBC >5 and received progesterone, women who had AF WBC<5 had lower rates of birth before 37 weeks (20% v 72%, p=0.047) and before 32 weeks (0% v 64% p=0.014). Women who received cerclage had longer latency days than those who received progesterone, (median 118.5 v 52, p=0.009). Cervical length at enrollment correlated to latency period, (r=0.4687, p=0.009). The Spearman's rank correlation coefficients for gestational age at delivery and AF glucose, LDH, or WBC count were not statistically significant.

Conclusion: Cervical length at the time of discovery of short cervix in the midtrimester ultrasound correlated to the latency period. In women with AF negative for inflammation and infection the outcome was improved. It remains to be determined if cervcal cerclage is beneficial in this subgroup.