European Journal of Cardiovascular Medicine

Preterm birth, defined as delivery before 37 completed weeks of gestation, remains a significant global health challenge, accounting for an estimated 11% of all live births and contributing to substantial neonatal morbidity and mortality [1]. Despite advances in obstetric care, the rate of preterm deliveries has remained relatively unchanged in many regions, underscoring the need for improved prediction and prevention strategies [2]. Numerous risk factors for preterm birth have been identified, including prior spontaneous miscarriage, which is associated with an increased likelihood of cervical insufficiency and early pregnancy loss [3].

Spontaneous miscarriage, particularly when recurrent or occurring in the second trimester, may lead to structural or functional compromise of the cervix [4]. The cervix plays a critical role in maintaining pregnancy, and its premature shortening can initiate a cascade of events resulting in preterm labor [5]. Transvaginal ultrasonographic measurement of cervical length has emerged as a reliable, non-invasive method to evaluate cervical competence and predict preterm delivery risk [6]. This modality is especially pertinent during the mid-trimester window (16–24 weeks), a period when interventions such as vaginal progesterone or cervical cerclage may still be effectively instituted [7].

Clinical guidelines recommend cervical length screening in high-risk women; however, the predictive value of cervical length in women with previous spontaneous miscarriages remains less thoroughly explored [8]. Many such women fall into a grey zone—not consistently identified as high-risk by traditional criteria—yet they may harbor subtle cervical changes that predispose them to adverse outcomes [9].

In this context, cervical length assessment could serve as a crucial tool in stratifying risk and guiding management in this subgroup. Identifying a specific cervical length threshold with high predictive value would enhance early intervention strategies and potentially reduce the incidence of spontaneous preterm birth [10].

The current study was undertaken to evaluate the association between mid-trimester cervical length and preterm birth in women with a prior history of spontaneous miscarriage.

This prospective observational study was conducted in the Department of Gynaecology and Obstetrics, Government Medical College, Bhupalpally, from June 2024 to May 2025. Ethical clearance was obtained from the Institutional Ethics Committee, and written informed consent was taken from all participants prior to enrollment.

Study Population

A total of 200 pregnant women were recruited based on the following

inclusion criteria:

• Singleton viable intrauterine pregnancy confirmed by ultrasound
• Gestational age between 16 and 24 weeks
• History of at least one spontaneous miscarriage (first or second trimester)

Exclusion criteria included:

• Multiple gestations
• Known uterine anomalies or fibroids
• History of cervical surgery (e.g., cone biopsy)
• Use of progesterone or cerclage before enrollment
• Medical disorders such as chronic hypertension, diabetes mellitus, or autoimmune conditions

Data Collection

After initial screening, participants underwent a detailed obstetric and medical history assessment. Gestational age was confirmed by first-trimester dating scans. Demographic details including maternal age, parity, BMI, and obstetric history were recorded.

All participants underwent transvaginal ultrasonography (TVS) using a high-frequency (7.5 MHz) probe in the dorsal lithotomy position. The cervical length (CL) was measured as the distance from the internal to the external os along the endocervical canal, avoiding undue pressure on the cervix. Measurements were taken three times by the same experienced radiologist, and the shortest value was recorded.

Participants were followed up till delivery. The primary outcome was incidence of preterm birth, defined as spontaneous onset of labor resulting in delivery before 37 completed weeks. Secondary outcomes included mode of delivery, neonatal birth weight, and NICU admissions.

Statistical Analysis

All data were entered and analyzed using SPSS version 26.0 (IBM Corp, Armonk, NY). Continuous variables were expressed as mean ± standard deviation, while categorical variables were summarized as frequencies and percentages. Comparison between groups (preterm vs. term delivery) was performed using:

• Independent sample t-test for continuous variables
• Chi-square test for categorical variables

Receiver Operating Characteristic (ROC) curve analysis was done to evaluate the predictive accuracy of cervical length for preterm birth. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for various CL cut-offs. A p-value <0.05 was considered statistically significant.

Table 1: Demographic Characteristics of Study Participants (n = 200)

Table 2: Delivery Outcomes and Cervical Length (n = 200)

Table 3: Secondary Maternal and Neonatal Outcomes

Table 4: Cervical Length Category and Preterm Birth Association

Table 5: Diagnostic Performance of Cervical Length <25 mm for Predicting Preterm Birth

Fig 1: ROC curve of cervical length predicting pre-term birth

The demographic analysis revealed that the average maternal age in the study population was 28.6 ± 4.2 years, and the mean BMI was 24.8 ± 3.6 kg/m². A significant proportion of participants (73%) were multigravida, and 32% had a history of two or more miscarriages. The mean gestational age at the time of cervical length measurement via transvaginal sonography was 19.4 ± 2.1 weeks.

In terms of delivery outcomes, women who experienced preterm birth had a substantially shorter mean cervical length of 24.1 ± 3.8 mm, compared to 32.3 ± 2.9 mm in those who delivered at term. This difference was statistically significant, suggesting a strong inverse relationship between cervical length and risk of preterm delivery.

Further analysis of neonatal and maternal outcomes indicated that preterm births were associated with poorer clinical parameters. The mean birth weight in the preterm group was 2140 ± 260 grams, in contrast to 2880 ± 330 grams among term births. NICU admission was required in 57.7% of preterm cases, while only 8.1% of term infants needed similar care. The cesarean delivery rate was also notably higher in the preterm group at 73.1%, compared to 37.8% among term deliveries.

When categorized by cervical length, 42 of 74 women with a length less than 25 mm delivered preterm, whereas only 10 of 126 women with cervical length ≥25 mm experienced preterm labor. This relationship was statistically significant, reinforcing the critical threshold value.

Diagnostic metrics for cervical length <25 mm showed a sensitivity of 80.8%, specificity of 78.4%, and a high negative predictive value of 92.1%. The ROC curve analysis yielded an AUC of 0.84 (95% CI: 0.78–0.89), indicating good diagnostic performance.

These results affirm that mid-trimester cervical length is a reliable predictor of preterm birth in women with prior miscarriage.

Preterm birth remains a persistent global health issue, particularly in pregnancies following spontaneous miscarriage, where cervical insufficiency may be a contributing factor. This study specifically evaluated the predictive role of mid-trimester cervical length in such women, aiming to establish its utility as an early diagnostic tool. The present findings demonstrated that a cervical length less than 25 mm between 16–24 weeks of gestation was significantly associated with an increased risk of preterm birth, with a sensitivity of 80.8%, specificity of 78.4%, and a high negative predictive value of 92.1%.

These findings are consistent with those reported by Iams et al., who conducted a large-scale prospective study involving 2,915 pregnant women. Their research demonstrated that women with a cervical length under 25 mm at 24 weeks had a nearly sixfold increase in the risk of delivering before 35 weeks, with a preterm birth rate of 18% compared to 4% in those with longer cervices [11]. In our cohort, 42 out of 74 women with a cervical length below 25 mm delivered preterm, emphasizing the robust association between early cervical shortening and adverse outcomes.

Hassan et al. also established the predictive utility of cervical length in a cohort of asymptomatic women between 19 and 24 weeks of gestation. Their study showed that a cervical length ≤25 mm was associated with a preterm birth rate of 28%, whereas those with a longer cervix had a rate of only 1.7% [12]. Our study mirrors these findings with a comparable preterm rate of 26%, reinforcing the use of this threshold as clinically meaningful in risk stratification.

Owen et al., in a randomized controlled trial assessing cerclage efficacy, evaluated women with a history of spontaneous second-trimester loss and cervical length below 25 mm. They found a preterm delivery rate of 30% in the control group and 14% in those who received cerclage, demonstrating the dual relevance of cervical length both as a predictor and a modifiable risk factor [13]. Although our study did not evaluate interventions, the baseline association between shortened cervix and preterm birth strongly supports the findings of Owen and colleagues.

Further supporting these observations, Berghella et al. performed a meta-analysis of cervical length screening in high-risk women, reporting a pooled sensitivity of 69% and specificity of 88% with a high negative predictive value for identifying women at risk of spontaneous preterm delivery  [14]. Our study exceeded these predictive values, particularly in sensitivity and NPV, suggesting that cervical length performs even more robustly when targeted to women with prior miscarriages.

These cumulative findings from multiple robust investigations converge with our results to confirm the strong predictive capacity of mid-trimester cervical length for preterm birth in a high-risk obstetric subgroup. The diagnostic performance of this single, non-invasive ultrasound marker demonstrates significant potential to guide antenatal surveillance and inform timely therapeutic decisions.

The findings of this study highlight the clinical value of mid-trimester cervical length measurement as a reliable and non-invasive predictor of preterm birth in women with a history of spontaneous miscarriage. A cervical length of less than 25 mm between 16 and 24 weeks of gestation was significantly associated with increased risk of preterm delivery, poorer neonatal outcomes, and higher rates of cesarean section and NICU admissions. The predictive accuracy demonstrated—particularly the high negative predictive value—supports its use in antenatal screening protocols for this high-risk group. Early identification of at-risk women through transvaginal ultrasound could facilitate timely interventions such as progesterone supplementation or cervical cerclage, ultimately improving maternal and neonatal outcomes.

Acknowledgements

The authors thank the Department of Obstetrics and Gynaecology at XXXX for providing institutional support and infrastructure for conducting this study.

Conflicts of Interest

The authors declare no conflicts of interest related to this study.

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