3. The presence of a funnel and the increased the risk of adverse perinatal outcome in patients with a short cervix.
This study was undertaken to determine whether the presence of a dilated internal os (funneling or beaking) alters the outcome of patients with a short cervix documented by transvaginal ultrasound in the second trimester. Between January 1998 and May 2004, all singleton pregnancies with a short cervix (< or =2.5 cm) and no funnel between 16 and 24 weeks' gestational age were identified by query and review of the Lehigh Valley Perinatal Ultrasound Database. These no funnel patients were compared with patients with a short cervix and funnel matched in accordance with cervical length and risk factors. Multiple variables of perinatal outcome were identified and compared between the Funnel and No Funnel groups. Correlations between cervical measurements and gestational age at birth were analyzed. Of the 279 patients with a short cervix identified, 82 were singleton with a T-shaped cervix and no funnel and 82 patients matched with a typical Y-shaped funnel. There was no difference between groups with respect to maternal demographics, previous preterm birth (28.1% No Funnel group vs 36.5% Funnel group, P = .3), prior cervical surgery (24.3% vs 22.0 %, P = .8), gestational age at entry (20.5 +/- 2.1 vs 21.1 +/- 2.4 weeks, P = .1), and cervical length (1.9 +/- 0.4 vs 1.8 +/- 0.5 cm , P = .1). The No Funnel group had significantly less readmissions for preterm labor (43.2% vs 67.1 %, P = .004), chorioamnionitis (2.4% vs 23.2 %, P = .0002), abruption (1.2% vs 13.4 %, P = .007), preterm rupture of membranes (6.1% vs 23.4%, P = .002), and cerclage placement (23.2% vs 43 %, P = .008). The neonates in the no funnel group delivered later (36.2% +/- 4.6 vs 33.8 +/- 5.4 weeks , P = .003), and had less morbidity and mortality (17.1% vs 37.8 %, P = .02) compared with the Funnel group. The width and depth of the funnel did not correlate with perinatal outcome. Cervical length ( R(2) = 0.07, P = .02) and cervical funneling as a categorical variable ( r = 0.3, P = .0002) did correlate with earlier delivery. It is concluded that the disruption of the internal os, as documented by funneling, is a significant risk factor for adverse perinatal outcome (ie, preterm labor, chorioamnionitis, abruption, rupture of the membranes, and serious neonatal morbidity and mortality). Cervical funneling is best measured as a categorical variable (present or absent).
Reference
Rust OA, Atlas RO, Kimmel S, Roberts WE, Hess LW. Does the presence of a funnel increase the risk of adverse perinatal outcome in a patient with a short cervix? Am J Obstet Gynecol. 2005 Apr;192(4):1060-6.
4. Screening for trisomy-21 and the presence or absence of the fetal nasal bone
To determine the benefit of including nasal bone assessment in addition to standard first-trimester markers (nuchal translucency, free beta human chorionic gonadotropin and pregnancy-associated plasma protein A) as a screening test for Down syndrome, using a strict criterion for classification of nasal bone absence. Nasal bone assessment was conducted in 2411 patients with crown-rump length between 45 and 84 mm, including 15 patients with Down syndrome. A patient was considered to have an absent nasal bone only if there was no evidence of present nasal bone. Unlike other studies, nasal bone was classified as present when there was evidence of a thin echogenic line under the skin. Simulation studies were conducted to assess the detection rate and false-positive rate of a combined first-trimester screening protocol including nasal bone assessment. There were 9 of 2396 (0.4%) unaffected cases with absent nasal bone (95% confidence interval 0.2%, 0.7%) and 8 of 15 (53.3%) Down syndrome cases (95% confidence interval 26.6%, 78.7%). Using a 1 in 250 risk cut-off, the detection rate of standard first-trimester screening was 87%, with a false-positive rate of 4.3%. Incorporating nasal bone measurement improved the detection rate of Down syndrome to 90% and reduced the false-positive rate to 2.5%. CONCLUSION: The use of a strict criterion to determine nasal bone absence leads to fewer cases classified as absent and may simplify the implementation of nasal bone as a marker for first-trimester screening, resulting in lower false-positives and higher detection, compared with other current screening protocols.
Reference
Orlandi F, Rossi C, Orlandi E, Jakil MC, Hallahan TW, Macri VJ, Krantz DA. First-trimester screening for trisomy-21 using a simplified method to assess the presence or absence of the fetal nasal bone. Am J Obstet Gynecol. 2005 Apr;192(4):1107-11.
