Routine transabdominal cervical length screening in mid-pregnancy for the prevention of preterm birth: Is it good enough to use as a screening test?

BACKGROUND: Preterm birth (PTB) is a major pregnancy complication. There is evidence that a short cervical length in mid-pregnancy may predict women at increased risk of PTB. AIMS: To evaluate the utility of population-based, transabdominal cervical length (TACL) measurement screening in mid-pregnancy for PTB prediction in women. MATERIALS AND METHODS: A transabdominal approach was initially performed, with a transvaginal (TVCL) approach offered when the TACL was <35 mm, could not be accurately measured, or the pregnancy had risk factors for PTB. TACL was compared to the directly related TVCL, when both were performed at the same assessment. Women with risk factors of PTB were included when they had both TACL and TVCL measurements performed at the same visit. RESULTS: Data were provided for 9355 singleton pregnancies from 13 participating imaging centres. A transabdominal approach was used in 9006 (96.3%), including 682 (7.3%) TVCL combined with TACL. There were 349 (3.7%) women who had TVCL only. The median TACL was longer (40 mm) than the TVCL (38 mm). In 682 paired TACL and TVCL measurements, TACL <35 mm correctly identified 96.2% of pregnancies with TVCL <25 mm, compared with 65.4% of cases when using a TACL <30 mm. A TVCL <25 mm occurred in 59 (0.6%) women. A TACL <35 mm was associated with birth <37 weeks of gestation in 12.1% of women and birth <32 weeks of gestation in 3.9%. CONCLUSIONS: Universal TACL is a feasible option for population screening of cervical length in a low-risk population, progressing to TVCL if the TACL is <35 mm or the cervix cannot be transabdominally accurately measured.

The perceptions of obstetric care providers about cervical length screening for preterm birth prevention.

BACKGROUND: Routine cervical length (CL) measurement at the mid-pregnancy ultrasound is a central recommendation of the Western Australian Preterm Birth Prevention Initiative (Initiative). AIM: To evaluate the perceptions and changes in practice of Western Australian obstetric care providers regarding routine CL screening for preterm birth (PTB) prevention following the Initiative introduction. METHODS: Two self-administered questionnaires were completed by providers from a range of practices. The first was during site visits with the Initiative Outreach team in 2015-2016. The questionnaire was re-issued in 2021 via online dissemination. Participant demographic data and opinions on CL screening for PTB prevention were collected. RESULTS: Two hundred and fourteen providers participated in 2015-2016 and 109 in 2021. In both surveys, providers were more likely to discuss transvaginal CL screening with high-risk women (48.1%, 76.1%; P < 0.001) compared with low-risk (7.5%, 18.3%; P = 0.002) and the importance of CL screening (13.5%, 40.4%; P < 0.001), in 2015-2016 and 2021, respectively. Responses relating to CL screening, including what constitutes a short cervix on ultrasound were varied. A transabdominal CL <35 mm was classified as short by 46.2% and 37.6% and <25 mm on transvaginal ultrasound by 49.1% and 64.2%, in the respective surveys. Most providers ceased progesterone (68.6%, 75.2%) at >28 weeks gestation. CONCLUSIONS: Providers focused on women with overt PTB risk factors, rather than a universal CL screening approach. Although there was improvement between the surveys, the definition of what constitutes a short cervix on ultrasound and how to treat and monitor women with a short CL remained varied.

The perceptions of pregnant women about cervical length screening for preterm birth prevention.

BACKGROUND: The Western Australian Preterm Birth Prevention Initiative was officially launched in November 2014. It demonstrated an initial decrease in the preterm birth rate in Western Australia. One of the key points of this initiative is the routine ultrasound measurement of the cervical length in mid-pregnancy. AIM: The aim of this study was to evaluate the perceptions and attitudes of Western Australian women regarding transvaginal cervical length (TVCL) screening for preterm birth prevention. MATERIALS AND METHODS: Self-administered questionnaires were completed by pregnant women before and after their mid-trimester obstetric ultrasound. Maternal demographical and medical data were collected in addition to opinions of TVCL screening. RESULTS: A total of 598 women participated with the maternal age range representative of the Western Australian obstetric population. There was a high rate of acceptance of TVCL imaging, with 2% of the 149 women declining a transvaginal ultrasound (TVU) offered in this study, 1.5% refusing a TVU in the past and 5.7% reporting that they would have a concern in having a TVU in the future. Women stated that they either had declined TVCL in the past (11%) or would decline in the future (30.7%) as they wanted to discuss the procedure with their clinician first, had been advised not to have a TVU by their clinician (11% in the past and 47.7% in the future) or felt uncomfortable with the operator (22% at a previous TVU and 34.4% in the future). CONCLUSION: Pregnant women participating in this study had a high acceptance of TVCL screening for preterm birth prevention.

Reducing preterm birth by a statewide multifaceted program: an implementation study.

BACKGROUND: A comprehensive preterm birth prevention program was introduced in the state of Western Australia encompassing new clinical guidelines, an outreach program for health care practitioners, a public health program for women and their families based on print and social media, and a new clinic at the state's sole tertiary level perinatal center for referral of those pregnant women at highest risk. The initiative had the single aim of safely lowering the rate of preterm birth. OBJECTIVE: The objective of the study was to evaluate the outcomes of the initiative on the rates of preterm birth both statewide and in the single tertiary level perinatal referral center. STUDY DESIGN: This was a prospective population-based cohort study of perinatal outcomes before and after 1 full year of implementation of the preterm birth prevention program. RESULTS: In the state overall, the rate of singleton preterm birth was reduced by 7.6% and was lower than in any of the preceding 6 years. This reduction amounted to 196 cases relative to the year before the introduction of the initiative and the effect extended from the 28-31 week gestational age group onward. Within the tertiary level center, the rate of preterm birth in 2015 was also significantly lower than in the preceding years. CONCLUSION: A comprehensive and multifaceted preterm birth prevention program aimed at both health care practitioners and the general public, operating within the environment of a government-funded universal health care system can significantly lower the rate of early birth. Further research is now required to increase the effect and to determine the relative contributions of each of the interventions.

Implementing universal cervical length screening in asymptomatic women with singleton pregnancies: challenges and opportunities.

Cervical length (CL) screening has been successfully utilised to identify asymptomatic women, with a singleton pregnancy, at risk of preterm birth (PTB), thereby providing an opportunity to offer interventions that may reduce that risk. Cervical length screening with ultrasound is most effectively performed with a transvaginal approach. Universal cervical length screening, encompassing all singleton pregnancies rather than restricting screening to those considered at increased risk of PTB, is currently not widely used, despite a growing body of evidence in support of its utility for PTB prevention. There are a number of barriers that may prevent or restrict the implementation of a universal CL screening program. These include cost, availability of vaginal progesterone and other treatment options, reluctance of women to undergo transvaginal ultrasound and the perceptions and beliefs of medical practitioners. Given that mid-pregnancy CL measurement is a recognised predictor of spontaneous PTB, that most cases of PTB occur with no prior maternal history and that there are interventions available that may reduce the risk of PTB, we believe there is a clear role for routine CL screening to be adopted as a component of the fetal morphology ultrasound examination. As a strategy to reduce PTB rates, discussion and counselling about PTB prevention and CL screening should be adopted as a core element of prenatal care.

A comparison of four fetal biometry growth charts within an Australian obstetric population.

PURPOSE: The aim of this study was to investigate the applicability of four existing fetal growth charts to a local tertiary hospital obstetric population. METHOD: Four existing fetal growth charts (the Raine study reference charts, INTERGROWTH-21st charts, World Health Organization (WHO) fetal growth study charts and Australasian Society for Ultrasound in Medicine (ASUM) endorsed Campbell Westerway charts were compared using data from 11651 singleton pregnancy ultrasound scans at King Edward Memorial Hospital (KEMH). The 3rd, 10th, 50th 90th and 97th percentile curves for abdominal circumference (AC) biometry for the KEMH data were calculated and the four primary correlation parameters from fitted 3rd order polynomials (a, b, c and d) were used to generate like-for-like comparisons for all charts. RESULTS: The overall comparisons showed a significant variation with different growth charts, giving different percentiles for the same fetal AC measurement. INTERGROWTH-21st percentile curves tended to fall below those of other charts for AC measurements. Both the Raine Study charts and ASUM charts were the charts of closest overall fit to the local data. CONCLUSION: Our data show the Raine Study charts are the most appropriate for our population compared with the other three charts assessed suggesting the 'one size fits all' model may not be appropriate. However, additional analysis of biometry measurements, primarily AC, is needed to address the deficiency of data at 14-18 weeks gestation which exists for the Raine Study data.A reasonable alternative may be to adopt the WHO charts with local calibration (including the 14 - 18 week gestation period).

Consistency in the transabdominal ultrasound measurement of cervical length in mid-pregnancy.

Purpose: The Western Australian Preterm Birth Prevention Initiative recommends a transabdominal cervical length (TACL) measurement at the mid-pregnancy ultrasound to screen low-risk women for preterm birth risk. In view of this recommendation, we assessed the inter-observer consistency of TACL screening in mid-pregnancy. Methods: Routinely collected mid-pregnancy TACL ultrasound images were graded from 0 to 4 according to the anatomical landmarks identified by a single expert. A random selection of 10 images of each grade were disseminated in an electronic survey to determine inter- and intra-observer variations in the classification of the cervical image. Results: A total of 244 participants graded 50 TACL images. Six participants repeated the grading. Overall agreement to the exact initial grade for all images was 49.6%, highest for images at both ends of the spectrum (83% Grade 0 and 70.4% for Grade 4). Overall agreement to the initial diagnostic Grades 3 and 4 was 75.3% (95% CI 74.5-76.0%) and was higher when the maternal bladder was empty. There was moderate inter-rater agreement (κ = 0.42) for Grades 3 and 4 (diagnostic) or Grades 1 and 2 (non-diagnostic). The intra-rater agreement was fair to good (κ = 0.59, 95% CI 0.49-0.70) for those who repeated the assessment (including the expert grader). Conclusions: Sonographic CL screening is considered an important tool for the identification of women at high risk of preterm birth. Image classification of TACL performed poorly compared with previous studies assessing transvaginal cervical length. Improved reliability and measurement consistency may be achieved through high levels of quality assurance, ongoing training and image audit.

The elements of success in a comprehensive state-wide program to safely reduce the rate of preterm birth.

BACKGROUND: In 2014, a whole-of-population and multi-faceted preterm birth prevention program was introduced in Western Australia with the single aim of safely lowering the rate of preterm birth. The program included new clinical guidelines, print and social media, and a dedicated new clinic. In the first full calendar year the rate of preterm birth fell by 7.6% and the reduction extended from the 28-31 week gestational age group upwards. OBJECTIVE: The objective of this study was to evaluate outcomes in greater depth and to also include the first three years of the program. STUDY DESIGN: This was a prospective population-based cohort study of perinatal outcomes in singleton pregnancies before and after commencement of the program. RESULTS: There was a significant reduction in preterm birth in the tertiary center which extended from 28 weeks gestation onwards and was ongoing. In non-tertiary centers there was an initial reduction, but this was not sustained past the first year. The greatest reduction was observed in pregnancies classified at first attendance as low risk. No benefit was observed in the private sector, but a significant reduction was seen in the remote region of the Kimberley where the program was first launched and vaginal progesterone had been made free-of-charge. CONCLUSION: Preterm birth rates can be safely reduced by a multi-faceted and whole-of-population program but the effectiveness requires continuing effort and will be greatest where the strategies are most targeted.