The preterm prediction study: Risk factors in twin gestations

The Change in Cervical Length Over Time as a Predictor of Preterm Delivery in Asymptomatic Women With Twin Pregnancies Who Have a Normal Mid-Trimester Cervical Length

“…The change in CL (expressed as a percentage) was defined as the decrement in sonographic CL between the initial and follow-up measurements and was calculated using the following formula: ([CL initial -CL follow-up ]/CL initial ) × 100, where CL is the cervical length in millimeters. A short CL was defined as ≤25 mm at 20-24 weeks' gestation, which has been validated in several studies (Goldenberg et al, 1996;Imseis et al, 1997). The study was approved by the Institutional Review Board of Seoul National University Bundang Hospital (Seongnamsi, Korea), and written informed consent was obtained from all study participants prior to enrollment.…”

“…We assumed that 5% of women with twin pregnancies and a CL > 25 mm at 20-24 weeks gestation have SPTDs at <32 weeks' gestation because previous studies have reported that the rate was 8.5-9.2% (Goldenberg et al, 1996;Guzman et al, 2000), and one half of women with SPTDs at <32 weeks' gestation have a CL > 25 mm at 20-24 weeks' gestation (Conde-Agudelo et al, 2010;Fox et al, 2009;Goldenberg et al, 1996;Yang et al, 2000). Therefore, using an alpha of 0.05 and a power of 0.8, we calculated that a sample size of 189 women would be needed to detect a 15% difference in the change in CL with a standard deviation (SD) of 16% (based on a pilot study).…”

“…Measurement of cervical length (CL) by transvaginal ultrasound (TVS) is known to be effective in identifying twin gestations at increased risk for preterm delivery (Goldenberg et al, 1996;Guzman et al, 2000;Souka et al, 1999;To et al, 2006;Yang et al, 2000). A recent meta-analysis indicated that among asymptomatic women with twin pregnancies, a CL ≤ 20 mm at 20-24 weeks' gestation is the most accurate in predicting preterm birth at <32 and <34 weeks' gestation, but a 'normal' CL (defined as a CL > 25 mm) was less accurate in predicting the absence of preterm birth (Conde-Agudelo et al, 2010).…”

“…A recent meta-analysis indicated that among asymptomatic women with twin pregnancies, a CL ≤ 20 mm at 20-24 weeks' gestation is the most accurate in predicting preterm birth at <32 and <34 weeks' gestation, but a 'normal' CL (defined as a CL > 25 mm) was less accurate in predicting the absence of preterm birth (Conde-Agudelo et al, 2010). Similarly, several studies have reported that approximately one half of women with spontaneous preterm delivery (SPTD) at < 32 weeks have a CL > 25 mm at 20-24 weeks (Conde-Agudelo et al, 2010;Fox et al, 2009;Goldenberg et al, 1996;Yang et al, 2000). At present, however, there is no effective tool to predict the risk of SPTD in the absence of a short CL, despite the fact that by identifying such a high-risk group for SPTD, possible interventions in this cohort can be studied to test their effectiveness.…”

Screening for Preterm Labor

“…Although the numbers of published trials in multiples are significantly fewer compared to singletons, sonographic assessment of the cervix appears to be of value in this population. Goldenberg et al, 50 prospectively screened 147 twin pregnancies at 24 and 28 weeks for more than 50 potential risk factors for spontaneous preterm birth. They found that at 24 weeks a cervical length < 25 mm was consistently associated with preterm birth.…”