This cluster non-randomized controlled trial aims to evaluate the effectiveness and feasibility of a risk score-guided targeted cervical length screening strategy for the prevention of spontaneous preterm birth in routine community-based prenatal care. Pregnant women are first assessed using a simple preterm birth risk scoring system, and those identified as high risk undergo transvaginal cervical length screening followed by guideline-based preventive interventions when clinically indicated.

The primary objective of the study is to compare this targeted screening strategy with usual prenatal care in reducing the incidence of spontaneous preterm birth occurring between 28 and 36 completed weeks of gestation. Secondary objectives include evaluating the cervical length screening rate, adherence to cervical length screening recommendations, and selected maternal and neonatal outcomes.

Researchers will compare outcomes between women receiving risk score-guided targeted screening and those receiving routine prenatal care without use of the risk scoring system. All participants will be followed until delivery.

1. Preterm birth is a leading cause of neonatal mortality, and current guidelines mainly recommend cervical length screening for women with a prior history of preterm birth, leaving many high-risk women without such a history unidentified. This study applies a validated early-pregnancy (<14 weeks' gestation) preterm birth risk scoring system based on 17 routinely collected clinical indicators to enable targeted risk stratification (e.g., 15 points for a previous preterm birth, 6 points for age <20 years, 3 points for age ≥35 years, 7 points for age ≥40 years, 1 point for BMI <18.5 kg/m², 7 points for diabetes mellitus, 5 points for chronic hypertension, 4 points for hyperthyroidism and diastolic blood pressure≥90 mmHg, 3 points for systolic blood pressure≥140 mmHg, 2 points for anaemia, 1 point for systolic blood pressure 120-139 mmHg). Screening efficiency is quantified using the number needed to screen (NNS) to support pragmatic clinical decision-making and resource allocation. The trial evaluates the effectiveness of implementing this risk-based screening strategy in real-world community settings.
2. Given the comparable maternal demographic profiles, historical preterm birth rates, levels of maternal health management, and healthcare accessibility in Yinzhou and Beilun districts, this study adopts a non-randomised, community-based cluster parallel controlled design. The intervention is implemented in Yinzhou District, while the control group is constructed using contemporaneous, anonymised maternal healthcare records from Beilun District obtained from the Ningbo Municipal Health Information Platform, with all required institutional and administrative approvals in place. Baseline comparability assessment and the use of geographically distinct data sources are intended to minimise confounding and intervention contamination, enabling evaluation of the effectiveness and feasibility of a standardised cervical length screening strategy in community settings.
3. The intervention group, located in Yinzhou District of Ningbo, will undergo assessment using the preterm birth risk scoring system. Women with a score >6 will be classified as high-risk and undergo cervical length screening via transvaginal ultrasonography. Those with a cervical length ≤25 mm will receive guideline-based standardised preventive interventions as clinically indicated. The control group, located in Beilun District of Ningbo, will receive routine prenatal care according to current clinical practice, without risk score assessment.
4. Pregnant women identified by transvaginal ultrasonography as having a cervical length ≤25 mm will be referred, according to a predefined standardised care pathway, to tertiary hospitals with established maternal-fetal medicine (MFM) services for further evaluation and management. Final assessment will be conducted by senior MFM specialists in accordance with current clinical guidelines, followed by implementation of preventive interventions. Vaginal progesterone therapy will be initiated in women without relevant high-risk obstetric history, while cervical cerclage will be performed in those meeting specific indications, such as a history of spontaneous mid-trimester pregnancy loss or preterm birth.
5. Community health service centers in both districts will use standardized tools to collect participants' baseline characteristics, screening information, intervention implementation, and pregnancy outcome data. Participants will be followed up until delivery, with primary assessment of pregnancy outcomes, including spontaneous preterm birth, et al.

Inclusion Criteria:

• ·For community health service centers:

  1. Be located in the selected districts

  2. Provide prenatal care and be responsible for the registration and follow-up management of pregnant women

  3. Have the chief physician (or equivalent) agree to participate and to implement study-related risk assessment, referral, follow-up, and data collection procedures, and to receive standardized training

     • For pregnant women:
  1. Registered at participating community health service centers.
  2. Singleton pregnancy.
  3. No history of previous cervical cerclage.
  4. Able and willing to provide written informed consent and participate in the study.

Exclusion Criteria:

• for pregnant women:

  1. Multiple pregnancies.
  2. History of cervical cerclage.
  3. Medical indications requiring pregnancy termination.
  4. Any other condition that, in the opinion of the investigator, would make the participant unsuitable for the study.