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128: Short cervix and negative fetal fibronectin: Low risk of delivery within 2 weeks of screening

      Objective

      Few reports exist regarding the performance of sonographic cervical length (CL) & Fetal Fibronectin (FFN) in patients (pts) at risk for PTD when CL is short (<2.5cm) & FFN is neg. We use a screening strategy in pts at high risk for PTD; obtain an FFN swab prior to CL, & only perform FFN screen if CL is <2.5cm; routinely administer a course of corticosteroids for pts at 24-34wks, with temporary tocolysis for contractions.

      Study Design

      In this retrospective study, we evaluated the time to delivery interval in all pts who had a CL and FFN within 24 hrs of CL in the University Obstetric Service. Using medical record review, we searched all pts having both CL and FFN result from 8/7/04 to 3/15/08. We identified 423 pts who met criteria for study. After excluding pts with multiple gestation, cerclage, & indicated delivery, we identified 114 singleton gestations with CL <2.5cm & FFN neg. If a pt delivered >1 time during the study period, only first pregnancy was used. For pts with multiple results, only the first CL and FFN results were evaluated. We analyzed the data using chi-square test, with significance set at p <0.05.

      Results

      Of 114 pts with CL <2.5cm & FFN neg, 2 & 3 pts delivered < 7days and <14 days of screening, resp. With FFN neg, the mean +/− SD time to delivery from CL <2.5cm (n=114), was 63 +/−28 days; CL <1.5cm (n=25): 66 +/−23 days; CL <0.5cm (n=4), 80 +/−12 days respectively.

      Conclusion

      Patients at risk for PTD who have a short cervix and negative FFN are very unlikely to deliver within 14 days of screening. Antenatal steroid administration in patients at high risk for PTD with a short cervix (CL <2.5cm) and with a negative FFN should be reconsidered.
      Tabled 1Results Table - Rate of Pre term delivery (%)
      GA first at FFN & CL (# pts)Deliv <14d; n (%)Deliv <37w; n (%)
      22 to < 24 wk (13)0 (0%)8 (61.5%)
      24 to < 28 wk (43)2 (4.6%)18 (41.8%)
      28 to < 32 wk (46)1 (2.2%)22 (47.8%)
      32 to < 34 wk (12)1 (8.3%)3 (25%)
      Total (114)4 (3.5%)51 (44.7.%)