Utility of follow-up cervical length screening in low-risk women with a cervical length of 26 to 29 mm

Screening for women at risk of spontaneous preterm birth, including cervical incompetence

Preterm births remain one of the biggest challenges in obstetrics worldwide. With the advancement of neonatal care, more premature neonates survive with long term consequences. Therefore, preventing or delaying preterm births starting from the preconceptional or antenatal periods are important. Among the numerous screening strategies described, not one can fit into all. Nonetheless, approaches including identifying women with modifiable risk factors for preterm births, genitourinary infections and short cervical length are the most useful. In this article, the current evidence is summarized and the best strategies for common clinical scenerios including cervical incompetence, history of second trimester loss or early preterm births, incidental short cervix and multiple pregnancy are discussed.

Randomized trial of screening for preterm birth in low-risk women - the preterm birth screening study

BACKGROUND

Preterm birth is a major cause of perinatal morbidity and mortality. It is unclear whether the introduction of a universal transvaginal ultrasound cervical length screening program in women at low risk for preterm delivery is associated with a reduction in the frequency of preterm birth.

OBJECTIVE

To test the hypothesis that the introduction of a midtrimester universal transvaginal ultrasound cervical length screening program in asymptomatic singleton pregnancies without prior preterm delivery would reduce the rate of preterm birth at <37 weeks of gestation.

STUDY DESIGN

This study was a multicenter nonblinded randomized trial of screening of asymptomatic singleton pregnancies without prior spontaneous preterm birth, who were randomized to either cervical length screening program (ie, intervention group) or no screening (ie, control group). Participants were randomized at the time of their routine anatomy scan between 18 0/7 and 23 6/7 weeks of gestation. Women randomized in the screening group received cervical length measurement. Those who were found to have cervical length ≤25 mm were offered 200 mg vaginal progesterone daily along with cervical pessary. The primary outcome was preterm birth at <37 weeks. The risk of primary outcome was quantified by the relative risk with 95% confidence interval, and was based on the intention-to-screen principle.

RESULTS

A total of 1334 asymptomatic women with singleton pregnancies and without prior preterm birth, were included in the trial. Out of the 675 women randomized in the transvaginal ultrasound cervical length screening group, 13 (1.9%) were found to have transvaginal ultrasound cervical length ≤25 mm during the screening. Preterm birth at <37 weeks of gestation occurred in 48 women in the transvaginal ultrasound cervical length screening group (7.5%), and 54 women in the control group (8.7%) (relative risk, 0.86; 95% confidence interval, 0.59-1.25). Women randomized in the transvaginal ultrasound cervical length screening group had no significant differences in the incidence of preterm birth at less than 34, 32, 30, 28, and 24 weeks of gestation.

CONCLUSION

The introduction of a universal transvaginal ultrasound cervical length screening program at 18 0/6 to 23 6/7 weeks of gestation in singleton pregnancies without prior spontaneous preterm birth, with treatment for those with cervical length ≤25 mm, did not result in significant lower incidence of preterm delivery than the incidence without the screening program.

Proposed staging criteria for sonographic and physical exam for cervical changes at <24 weeks gestation to predict preterm birth

Asymptomatic cervical changes, such as cervical length shortening and dilation, which often occur before spontaneous preterm birth, have been described well in singleton pregnancies with or without history of preterm birth. The current screening strategies available to identify patients at increased risk of spontaneous preterm birth include use of transvaginal ultrasound for cervical length assessment and for detection of a short cervical length (≤25 mm) before 24 weeks of gestation. Whether an additional evaluation of the cervix (ie, via speculum or manual exam) is indicated is often pondered by clinicians and may depend on how short the cervical length is and if there is a history of preterm birth. Based on expert opinion, we developed a novel staging system of asymptomatic cervical changes including the following: cervical length measurement, cervical and membrane appearance on speculum exam, and cervical dilation by manual exam. This staging system, if proven accurate, may aid in standardizing definitions for purposes of patient prognosis, evaluation of intervention efficacy, and clinical management.

Vaginal progesterone compared with intramuscular 17-alpha-hydroxyprogesterone caproate for prevention of recurrent preterm birth in singleton gestations: a systematic review and meta-analysis

OBJECTIVE

Randomized trials have found benefits of both vaginal progesterone and 17-alpha-hydroxyprogesterone caproate in the prevention of recurrent preterm birth. A previous meta-analysis directly comparing the two was limited by low-quality evidence, and national and international society guidelines remain conflicting regarding progestin formulation recommended for prevention of recurrent preterm birth. The aim of this updated systematic review with meta-analysis was to evaluate the efficacy of vaginal progesterone compared with 17-alpha-hydroxyprogesterone caproate in the prevention of spontaneous preterm birth in patients with singleton gestations and previous spontaneous preterm birth.

DATA SOURCES

Searches were performed in MEDLINE, Ovid, Scopus, ClinicalTrials.gov, the International Prospective Register of Systematic Reviews (PROSPERO), SciELO, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) with the use of a combination of keywords and text words related to "preterm birth," "preterm delivery," "singleton," "cervical length," "progesterone," "progestogens," "vaginal," "17-alpha-hydroxy-progesterone caproate," and "intramuscular" from inception of each database to September 2021. No restrictions for language or geographic location were applied.

STUDY ELIGIBILITY CRITERIA

We included all randomized controlled trials of asymptomatic singleton gestations with previous spontaneous preterm birth that were randomized to prophylactic treatment with either vaginal progesterone (ie, intervention group) or intramuscular 17-alpha-hydroxyprogesterone caproate (ie, comparison group). Post hoc sensitivity analysis was performed for studies with low risk of bias and studies with protocol registration.

METHODS

The primary outcome was preterm birth <34 weeks' gestation. The summary measures were reported as relative risks with 95% confidence intervals.

RESULTS

Seven randomized controlled trials including 1910 patients were included in the meta-analysis. Patients who received vaginal progesterone had a significantly lower rate of preterm birth at <34 weeks (14.7% vs 19.9%; relative risk, 0.74; 95% confidence interval, 0.57-0.96), preterm birth at <37 weeks (36.0% vs 46.6%; relative risk, 0.76; 95% confidence interval, 0.69-0.85), and preterm birth at <32 weeks of gestation (7.9% vs 13.6%; relative risk, 0.58; 95% confidence interval, 0.39-0.86), compared with women who received intramuscular 17-alpha-hydroxyprogesterone caproate. There were no significant differences in the rate of preterm birth at <28 weeks' gestation. Adverse drug reactions were significantly lower in the vaginal progesterone group than in the 17-alpha-hydroxyprogesterone caproate group (15.6% vs 22.2%; relative risk, 0.71; 95% confidence interval, 0.54-0.92). Perinatal mortality was lower in the vaginal progesterone group than in the 17-alpha-hydroxyprogesterone caproate group (2.2% vs 4.4%; relative risk, 0.51; 95% confidence interval, 0.25-1.01). In sensitivity analysis including trials rated with at least 4 Cochrane tools as of "low risk of bias," 4 trials were included (N=575), and there was no longer a significant difference in preterm birth at <34 weeks' gestation between vaginal progesterone and 17-alpha-hydroxyprogesterone caproate (12.2% vs 13.9%; relative risk, 0.87; 95% confidence interval, 0.57-1.32).

CONCLUSION

Overall, vaginal progesterone was superior to 17-alpha-hydroxyprogesterone caproate in the prevention of preterm birth at <34 weeks' gestation in singleton pregnancies with previous spontaneous preterm birth. Although sensitivity analysis of high-fidelity studies showed the same trend, findings were no longer statistically significant.

Evaluation of midtrimester cervical length thresholds for the prediction of spontaneous preterm birth

INTRODUCTION

To estimate the optimal midtrimester cervical length (CL) threshold for the prediction of spontaneous preterm birth (sPTB) in asymptomatic pregnant women.

MATERIAL AND METHODS

This is a prospective observational cohort study including asymptomatic women with singleton pregnancies who underwent CL measurement by transabdominal and/or transvaginal ultrasound between 19°^/7 and 21^6/7 weeks of gestation. All CL ≤30 mm from transabdominal ultrasound were confirmed by transvaginal ultrasound. Primary outcomes were sPTB <35 and <37 weeks.

RESULTS

Out of 3,449 participants, 28 (0.8%) had a sPTB before 35 weeks and 99 (2.9%) had a sPTB before 37 weeks. Receiver operating characteristics (ROC) curves suggest that a cut-off of 30 mm was the optimal CL to predict sPTB before 35 weeks (sensitivity: 43%; specificity: 97%) and sPTB before 37 weeks (sensitivity: 21%; specificity: 97%). While a CL <25 mm was an important risk factor for sPTB before 35 weeks (relative risk: 31; 95% confidence interval: 13-73), women with a CL between 25 and 30 mm were also at greater risk (relative risk: 12; 95% confidence interval: 4 - 35) compared to women with CL ≥30 mm.

DISCUSSION

A midtrimester CL <30 mm should be considered to identify women at high-risk of sPTB.