Transvaginal sonography useful option for predicting Preterm delivery
Preterm birth as defined by WHO, American academy of Paediatrics and American Congress of Obstetrician and Gynaecologist, is the birth of a baby before 37 weeks of gestation. Preterm labour has multifactorial etiopathogenesis. A variety of maternal and fetal factors are known to increase the risk of preterm labour. Although there are unique aspects to each cause of preterm labour these diverse processes culminate in common end point which is premature cervical dilation and effacement premature activation of uterine contractions.
The fundamental change in the strategy of the preterm birth prevention has been the understanding of a need to intervene earlier in the development of a pathophysiology leading to this undesired outcome of preterm labour.
Several methods like home uterine monitoring, cervical examination, fetal fibronectin in cervico-vaginal secretions etc. have been used for identifying women at risk of preterm delivery. But these methods have been associated with either low sensitivity or specificity or are not cost effective. Sonographic evaluation of cervix determined by transabdominal or trans-vaginal scanning has significant role to predict the preterm labour. Sonographic evaluation is more precise procedure as compared to digital assessment. When performed by trained operator cervical length analysis using TVS is safe, highly reproducible more predictive than TAS screening.
The present study was carried out by Arora et al. in tertiary care teaching hospital for 1 year from 1 Jan 2019 to 31 Dec 2019. Total of 100 study participants who underwent TVS assessments of cervix regularly followed up who underwent TVS assessment of cervix and were regularly follow up and delivered.
The mean cervical length in all these women was 30±6.68 mm. It was observed that 51.72% of patients with short cervical length less than 25 mm had preterm labour compared to the patients with cervical length more than 25mm i.e. 4.22%.
Though preterm birth occurs in approximately 5-15% of all deliveries it accounts for the major bulk of perinatal and especially postnatal deaths. The risk of neonatal morbidity and mortality mainly depends on the gestational age at delivery. Survival rate increases with increasing period of gestation. In a developing country like ours, where intensive care facilities are often unavailable, mortality figures would be much higher at a lower gestation period at delivery.
The main reason for low success rate of tocolytic therapy is failure to detect patient at an early stage. Thus it becomes essential to identify women, both symptomatic and asymptomatic, who are at risk of preterm delivery early enough so that an optimum treatment in the form of tocolysis or cerclage can be given in time. Unfortunately current methods of identifying women at risk of preterm delivery like a scoring system based on demographic factors and digital examination of cervix have low sensitivity and specificity. Objective methods such as evaluation of the presence of cervico-vaginal fibronectin, direct or indirect assessment of subclinical infection including bacterial vaginosis, and assessment of cervical or amniotic cytokine concentration are accurate, but expensive and often unavailable.
Ultrasonographic assessment of the cervix has emerged as an alternative method to objectively assess cervical length and morphology for prediction of preterm labour. Acceptability and repeatability of this procedure were found to be good and cost- effective
Short cervical length predispose to preterm labour. The risk of preterm delivery is inversely proportional to cervical length. Doing a TVS measurement of cervical length between 20-25 weeks of gestation can be a helpful strategy to identify pregnant women at risk of preterm delivery.
Source: Arora et al. / Indian Journal of Obstetrics and Gynecology Research 2021;8(4):531–534
https://doi.org/10.18231/j.ijogr.2021.109
