Reference Ranges for Ultrasonographic Measurements of the Uterine Cervix in Low-Risk Pregnant Women

Abstract

Objective To define transvaginal ultrasound reference ranges for uterine cervix measurements according to gestational age (GA) in low-risk pregnancies.

Methods Cohort of low-risk pregnant women undergoing transvaginal ultrasound exams every 4 weeks, comprising measurements of the cervical length and volume, the transverse and anteroposterior diameters of the cervix, and distance from the entrance of the uterine artery into the cervix until the internal os. The inter- and intraobserver variabilities were assessed with the linear correlation coefficient and the Student t-test. Within each period of GA, 2.5, 10, 50, 90 and 97.5 percentiles were estimated, and the variation by GA was assessed with analysis of variance for dependent samples. Mean values and Student t-test were used to compare the values stratified by control variables.

Results After confirming the high reproducibility of the method, 172 women followed in this cohort presented a reduction in cervical length, with an increase in volume and in the anteroposterior and transverse diameters during pregnancy. Smaller cervical lengths were associated with younger age, lower parity, and absence of previous cesarean section (C-section).

Conclusion In the studied population, we observed cervical length shortening throughout pregnancy, suggesting a physiological reduction mainly in the vaginal portion of the cervix. In order to better predict preterm birth, cervical insufficiency and premature rupture of membranes, reference curves and specific cut-off values need to be validated.

Resumo

Objetivo Elaborar curvas de referências de medidas ultrassonográficas de colo uterino por idade gestacional (IG) em gestações de baixo risco.

Métodos Coorte de gestantes de baixo risco, submetidas a ultrassom transvaginal repetido a cada 4 semanas, com medida do comprimento, dos diâmetros antero-posterior e transverso, da distância entre a entrada da artéria uterina no colo e o orifício interno, e do volume do colo. Foi avaliada a variabilidade inter e intraobservador entre as medidas com o coeficiente de correlação linear e teste t de Student. Para cada faixa de IG, estimaram-se os percentis 2,5, 10, 50, 90 e 97,5 dos valores das medidas, com a variação por IG avaliada por análise de variância para amostras dependentes. As comparações dos valores por variáveis de controle foram feitas por meio dos cálculos de médias e teste t de Student.

Resultados Assegurada a alta reprodutibilidade do método, as 172 mulheres acompanhadas na coorte apresentaram redução das medidas de comprimento de colo com o decorrer da gestação, com aumento de volume e dos diâmetros anteroposterior e transverso. O menor comprimento cervical foi associado à menor idade materna, menor paridade, e ausência de cesárea prévia.

Conclusão Na população estudada foi observada redução no comprimento cervical com o decorrer da gestação, sugerindo encurtamento fisiológico principalmente à custa da porção vaginal do colo. Há a necessidade de validar tais curvas de referência e pontos de corte específicos para uma melhor predição de risco de parto pré-termo, insuficiência cervical, e amniorrexe prematura.

Keywords

ultrasound - uterine cervix - cervical length - reference ranges - low-risk pregnancy

Palavras-chave

ultrassom - colo uterino - comprimento cervical - valores de referência - gestação de baixo risco

Contributors

Andrade KC, Bortoletto TG, Almeida CM, Daniel RA, Avo H, Pacagnella RC, and Cecatti JG contributed to the conception of the study, the critical review of the intellectual content, and the final approval of the version to be published.

• References

• 1 Preterm birth: Fact Sheet. World Health Organization Web site. Published November 2016. http://www.who.int/mediacentre/factsheets/fs363/en/ . Accessed March 10, 2017
• 2 Blencowe H, Cousens S, Chou D. , et al; Born Too Soon Preterm Birth Action Group. Born too soon: the global epidemiology of 15 million preterm births. Reprod Health 2013; 10 (Suppl. 01) S2
• 3 Koullali B, Oudijk MA, Nijman TA, Mol BW, Pajkrt E. Risk assessment and management to prevent preterm birth. Semin Fetal Neonatal Med 2016; 21 (02) 80-88
• 4 Buck JN, Orzechowski KM, Berghella V. Racial disparities in cervical length for prediction of preterm birth in a low risk population. J Matern Fetal Neonatal Med 2017; 30 (15) 1851-1854
• 5 Bittar RE, Zugaib M. [Risk predictors for preterm birth]. Rev Bras Ginecol Obstet 2009; 31 (04) 203-209
• 6 Manuck TA, Esplin MS, Biggio J. , et al; Eunice Kennedy Shriver National Institute of Child Health and Human Development Genomics and Proteomics Network for Preterm Birth Research. The phenotype of spontaneous preterm birth: application of a clinical phenotyping tool. Am J Obstet Gynecol 2015; 212 (04) 487.e1-487.e11
• 7 Romero R, Nicolaides K, Conde-Agudelo A. , et al. Vaginal progesterone in women with an asymptomatic sonographic short cervix in the mid-trimester decreases preterm delivery and neonatal morbidity: a systematic review and metaanalysis of individual patient data. Am J Obstet Gynecol 2012; 206: 124.e1-124.e19
• 8 Conde-Agudelo A, Romero R. Predictive accuracy of changes in transvaginal sonographic cervical length over time for preterm birth: a systematic review and metaanalysis. Am J Obstet Gynecol 2015; 213 (06) 789-801
• 9 Li Q, Reeves M, Owen J, Keith LG. Precocious cervical ripening as a screening target to predict spontaneous preterm delivery among asymptomatic singleton pregnancies: a systematic review. Am J Obstet Gynecol 2015; 212 (02) 145-156
• 10 House M, Kaplan DL, Socrate S. Relationships between mechanical properties and extracellular matrix constituents of the cervical stroma during pregnancy. Semin Perinatol 2009; 33 (05) 300-307
• 11 Sinno A, Usta IM, Nassar AH. A short cervical length in pregnancy: management options. Am J Perinatol 2009; 26 (10) 761-770
• 12 Vaisbuch E, Romero R, Erez O. , et al. Clinical significance of early (< 20 weeks) vs. late (20-24 weeks) detection of sonographic short cervix in asymptomatic women in the mid-trimester. Ultrasound Obstet Gynecol 2010; 36 (04) 471-481
• 13 Suhag A, Berghella V. Short cervical length dilemma. Obstet Gynecol Clin North Am 2015; 42 (02) 241-254
• 14 Romero R, Nicolaides KH, Conde-Agudelo A. , et al. Vaginal progesterone decreases preterm birth ≤ 34 weeks of gestation in women with a singleton pregnancy and a short cervix: an updated meta-analysis including data from the OPPTIMUM study. Ultrasound Obstet Gynecol 2016; 48 (03) 308-317
• 15 Abdel-Aleem H, Shaaban OM, Abdel-Aleem MA. Cervical pessary for preventing preterm birth. Cochrane Database Syst Rev 2013; (05) CD007873
• 16 Fox NS, Rebarber A, Roman AS, Klauser CK, Saltzman DH. Association between second-trimester cervical length and spontaneous preterm birth in twin pregnancies. J Ultrasound Med 2010; 29 (12) 1733-1739
• 17 Ramaeker DM, Simhan HN. Sonographic cervical length, vaginal bleeding, and the risk of preterm birth. Am J Obstet Gynecol 2012; 206 (03) 224.e1-224.e4
• 18 Wozniak S, Czuczwar P, Szkodziak P, Milart P, Wozniakowska E, Paszkowski T. Elastography in predicting preterm delivery in asymptomatic, low-risk women: a prospective observational study. BMC Pregnancy Childbirth 2014; 14: 238
• 19 Kuusela P, Jacobsson B, Söderlund M. , et al. Transvaginal sonographic evaluation of cervical length in the second trimester of asymptomatic singleton pregnancies, and the risk of preterm delivery. Acta Obstet Gynecol Scand 2015; 94 (06) 598-607
• 20 Miller ES, Tita AT, Grobman WA. Second-trimester cervical length screening among asymptomatic women: an evaluation of risk-based strategies. Obstet Gynecol 2015; 126 (01) 61-66
• 21 Heath VC, Southall TR, Souka AP, Novakov A, Nicolaides KH. Cervical length at 23 weeks of gestation: relation to demographic characteristics and previous obstetric history. Ultrasound Obstet Gynecol 1998; 12 (05) 304-311
• 22 Podobnik M, Bulić M, Smiljanić N, Bistricki J. Ultrasonography in the detection of cervical incompetency. J Clin Ultrasound 1988; 16 (06) 383-391
• 23 Guzman ER, Ananth CV. Cervical length and spontaneous prematurity: laying the foundation for future interventional randomized trials for the short cervix. Ultrasound Obstet Gynecol 2001; 18 (03) 195-199
• 24 Silva SV, Damião R, Fonseca EB, Garcia S, Lippi UG. Reference ranges for cervical length by transvaginal scan in singleton pregnancies. J Matern Fetal Neonatal Med 2010; 23 (05) 379-382
• 25 Palma-Dias RS, Fonseca MM, Stein NR, Schmidt AP, Magalhães JA. Relation of cervical length at 22-24 weeks of gestation to demographic characteristics and obstetric history. Braz J Med Biol Res 2004; 37 (05) 737-744
• 26 Hoesli IM, Strutas D, Tercanli S, Holzgreve W. Charts for cervical length in singleton pregnancy. Int J Gynaecol Obstet 2003; 82 (02) 161-165
• 27 Peng CR, Chen CP, Wang KG, Wang LK, Chen CY, Chen YY. The reliability of transabdominal cervical length measurement in a low-risk obstetric population: Comparison with transvaginal measurement. Taiwan J Obstet Gynecol 2015; 54 (02) 167-171
• 28 Friedman AM, Schwartz N, Ludmir J, Parry S, Bastek JA, Sehdev HM. Can transabdominal ultrasound identify women at high risk for short cervical length?. Acta Obstet Gynecol Scand 2013; 92 (06) 637-641
• 29 Hernandez-Andrade E, Romero R, Ahn H. , et al. Transabdominal evaluation of uterine cervical length during pregnancy fails to identify a substantial number of women with a short cervix. J Matern Fetal Neonatal Med 2012; 25 (09) 1682-1689
• 30 To MS, Skentou CA, Royston P, Yu CKH, Nicolaides KH. Prediction of patient-specific risk of early preterm delivery using maternal history and sonographic measurement of cervical length: a population-based prospective study. Ultrasound Obstet Gynecol 2006; 27 (04) 362-367
• 31 Domin CM, Smith EJ, Terplan M. Transvaginal ultrasonographic measurement of cervical length as a predictor of preterm birth: a systematic review with meta-analysis. Ultrasound Q 2010; 26 (04) 241-248
• 32 Conde-Agudelo A, Romero R, Nicolaides K. , et al. Vaginal progesterone vs. cervical cerclage for the prevention of preterm birth in women with a sonographic short cervix, previous preterm birth, and singleton gestation: a systematic review and indirect comparison metaanalysis. Am J Obstet Gynecol 2013; 208 (01) 42.e1-42.e18
• 33 Mercer BM, Goldenberg RL, Das A. , et al. The preterm prediction study: a clinical risk assessment system. Am J Obstet Gynecol 1996; 174 (06) 1885-1893 , discussion 1893–1895
• 34 Passini Jr R, Cecatti JG, Lajos GJ. , et al; Brazilian Multicentre Study on Preterm Birth study group. Brazilian multicentre study on preterm birth (EMIP): prevalence and factors associated with spontaneous preterm birth. PLoS One 2014; 9 (10) e109069
• 35 Szychowski JM, Owen J, Hankins G. , et al; Vaginal Ultrasound Cerclage Trial Consortium. Timing of mid-trimester cervical length shortening in high-risk women. Ultrasound Obstet Gynecol 2009; 33 (01) 70-75