Cervical length as a predictive tool in managing preterm labour risks: Study

Nearly two-thirds of preterm births are spontaneous, often resulting from either the early stat of labour or preterm premature rupture of membranes (PPROM). The remaining one-third of preterm births are induced due to maternal or foetal complications. Preterm labour can occur at various gestational ages and through different mechanisms. While term labour is initiated by physiological activation of the labour pathways, preterm labour is often triggered by pathological factors that activate one or more components of the same pathway. The pathway, which involves uterine contractions, cervical dilation, and membrane activation, is consistent across both term and preterm labour.

Identifying women at risk for preterm labour early is very crucial, particularly due to the recent increase in preterm births. While advancements in neonatal care have improved survival rates for very premature infants, early detection of preterm birth risk remains essential. Therefore, developing a very sensitive approach to diagnose women at high risk and implementing effective prevention strategies for preterm labour is of paramount importance.

Cervical length measurement is considered the gold standard for detecting preterm birth risk. Since eighties (1980), transvaginal ultrasonography (TVU) has been used to measure length of cervix, offering a simple, non-invasive, and accessible tool for identifying pregnant women at high risk for PTD. TVU can be integrated with routine nuchal translucency (NT) and anomaly scans to enhance early detection. In some cases, early recognition of a shortened cervical length can lead to interventions that may reduce the likelihood of PTB.

Research has shown that using 17αhydroxyprogesterone caproate, micronized progesterone, and cervical cerclage can help prevent preterm birth. Measuring cervical length during the first trimester NT scan (10 to 14 weeks) and repeating the measurement during the second trimester anomaly scan (20 to 24 weeks) while monitoring the rate of shortening is a valuable indicator for predicting PTL. Although no statistically significant difference in cervical lengths between term and non-term pregnancies has been observed during TVS at 10 to 14 weeks, this method provides a useful baseline for monitoring.

The predictive accuracy for spontaneous preterm delivery varies based on factors such as the number of foetuses, gestational age during testing, cervical length, and the presence of preterm birth risk factors. While a short cervical length is associated with preterm delivery, it remains unclear whether this condition is a cause or a consequence of pathophysiological processes.

A prospective cohort design was employed, involving 70 asymptomatic pregnant women aged 18-35 with singleton pregnancies, cervical lengths >25 mm, and no history of cervical issues. Length of cervix was measured using TVS at 10-14 weeks and 20-24 weeks of gestation and pregnancy outcome was noted. Regression models were used to analyse the relationship between preterm labour and cervical length changes.

The study found that preterm labour occurred in 30% of patients, predominantly in those with cervical lengths under 26 mm during the second measurement. Significant differences in cervical length were observed between pregnancies under and over 37 weeks. Cervical length measurement demonstrated a specificity of 90.91% and a sensitivity of 76.19% in predicting preterm labour.

This study's results highlight the significance of measuring cervical length as a predictor of premature labour. The statistics showed that most patients were between the ages of 26 and 30, which is a crucial reproductive period. The even distribution between first-time mothers (PRIMI) and those with previous pregnancies (MULTI) suggests that parity alone is not a significant predictor of preterm labour within this sample. The gestational age measurements at 10 and 20 weeks provide key insights into common periods for evaluating cervical length changes. Notably, preterm labour was significantly associated with shorter cervical lengths, particularly those less than 26 mm during the second measurement. Consistent with previous research, this data confirms that shorter cervical lengths raise the likelihood of premature delivery.

This study highlights the significant association between cervical length and the risk of preterm labour. Notably, 30% of the patients experienced preterm labour, predominantly among those with a length of cervix less than 26 mm during the second assessment. Length of cervix emerged as a strong predictor of preterm labor, with significant differences observed between pregnancies that lasted less than 37 weeks and those that exceeded this gestational period. Patients who delivered before 37 weeks had a shorter cervical length, with more substantial mean rate and absolute changes, emphasizing the dynamic nature of cervical shortening as a risk factor for preterm labour. Vaginal delivery was the predominant mode of birth, followed by caesarean sections (LSCS). The high sensitivity and specificity of cervical length measurements underscore their effectiveness as a predictive tool in managing pregnancy outcomes.

Overall, the findings support the importance of cervical length evaluation in prenatal care, especially for identifying and managing the risk of preterm labour. Shorter cervical lengths were consistently associated with higher risks of early delivery, reinforcing the need for regular monitoring. Implementing standardized cervical length assessments could significantly improve early detection and intervention strategies, ultimately enhancing maternal and neonatal health outcomes.

Source: Gopalan et al. / Indian Journal of Obstetrics and Gynecology Research 2025;12(3):427–431