The investigators propose a prospective evaluation of methods to assess cervical length for uncomplicated singleton gestations between 18-28 weeks presenting to the MFM office for routine mid pregnancy ultrasound. The investigators hypothesize that a sequential approach to screening of the cervix (which consists of initial transabdominal evaluation first with transvaginal ultrasound reserved only for those patients in whom the cervix appears short on transabdominal exam or when adequate views cannot be obtained with the transabdominal approach alone) will take less time, will result in the same number of adequate views of the cervix and will have higher patient satisfaction that a universal transvaginal screening approach.

OBJECTIVE

To determine the best strategy for cervical length screening in uncomplicated singleton gestations between the gestational ages of 18-28 weeks.

Primary outcome:

1) Time required to obtain adequate views of the cervical length.

Secondary outcomes:

1. Patient satisfaction with ultrasound experience as measured by patient questionnaire
2. Number of adequate views of the cervix obtained with each approach

STUDY DESIGN

This is a prospective study to compare strategies for cervical length measurements in uncomplicated singleton gestations seen in the MFM office for routine mid pregnancy fetal well being ultrasound between 18-28 weeks gestation. The different strategies include 1) Transabdominal assessment of the cervix (current standard), 2) Sequential evaluation of the cervical length (transabdominal followed by transvaginal if necessary due to short cervix or inadequate transabdominal views), and 3) Transvaginal cervical length assessment. Patients with an uncomplicated singleton gestation presenting for a routine mid pregnancy ultrasound between 18-28 weeks will be randomized into one of the three groups noted above after consent is obtained. Ultrasound examination will then take place and data collected. The various strategies listed above will be compared for the following:

1. Time required to obtain views of the cervix

   1. Time from initiation of exam to completion of cervical assessment
   2. Time for completion of entire exam

2. Patient satisfaction

   1. Comfort/Discomfort of exam procedure
   2. Overall impression of exam process

3. Number of adequate views of the cervix obtained

Maternal demographics including age, parity, weight, height and due date/gestational age will also be obtained for all consenting patients.

BACKGROUND AND SIGNIFICANCE

Preterm birth is a significant problem in the United States and worldwide. Approximately twelve percent of births in the US occur before 37 weeks and are considered preterm. Of these, 80% are considered "spontaneous preterm deliveries" (as opposed to iatrogenic) and are related to preterm labor or preterm rupture of membranes (Arias, 2003). Certain pregnancy characteristics have been identified to determine those patients at risk for preterm delivery. These include a history of preterm birth (Esplin, 2008), uterine anomalies, multiple gestation, among other things, both modifiable and not (Gardosi, 2000; Ananth, 2006). However, an important risk factor that can be identified is the presence of specific changes in the cervix, such as cervical shortening, and in fact, studies indicate that the risk of spontaneous preterm birth increases as cervical length decreases (Iams, 1996; Hibbard, 2000).

Some authors now advocate the universal screening of all pregnant women for cervical shortening at the time of the ultrasound that is performed at 18-28 weeks in most women. However, the best approach to evaluate the cervix in low risk patients (those without an identifiable risk factor) remains controversial.

PROTOCOL

1. Patients will be identified in the Maternal Fetal Medicine office and consented for randomization at the time of presentation for previously scheduled mid-trimester ultrasound

2. Patients will be given randomly generated treatment allocations within sealed opaque envelopes. Once a patient has consented to enter the trial, the envelope will be opened by the ultrasonographer to determine the assigned treatment regimen.

3. Patients will be randomized into one of three groups:

   1. Standard US evaluation
   2. Sequential US evaluation
   3. Transvaginal cervical length screening

4. Maternal demographics including maternal age, height, weight, parity, and gestational age will be collected from the patient as part of the patient questionnaire. Ultrasound exam data including measurements of the fetal biometry, presence of fetal anomalies, placental location and amniotic fluid volume will be collected from the official ultrasound report.

   1. Patients will be assigned a unique study ID number at the time of enrollment and all information including time of ultrasound procedures, clinical data and adequacy of cervical measurement will be linked by the ID number
   2. All data will be entered into an electronic data base in a de-identified fashion and kept in a secure, encrypted web-based database management program (RedCap).

Inclusion Criteria:

• singleton gestation
• between 18-28 weeks

Exclusion Criteria:

• presence of cerclage
• known short cervix
• prior preterm birth