Parto pré-termo espontâneo sem rotura de membranas: prevalência, fatores de risco e o papel do colo uterino / Spontaneous preterm birth without premature rupture of membranes: prevalence, risk factors and the role of the cervix

Cerca de 15 milhões de prematuros nascem por ano globalmente. Em 2015 ocorreram mais de 4 milhões de mortes de crianças menores de 5 anos, e as complicações da prematuridade são a principal causa de óbito em neonatos. O parto pré-termo é uma síndrome em que múltiplas etiologias convergem para uma via final única, e os fatores de risco mais importantes são antecedente de prematuridade e gestação gemelar. O colo uterino tem a função de manter a gestação desde a concepção até o parto, e seu processo de amadurecimento gera esvaecimento, dilatação e encurtamento, num continuum que pode compreender desde quadros de insuficiência cervical até o parto pré-termo espontâneo sem rotura de membranas. Este primeiro artigo, da série de três, descreve a prevalência da prematuridade, seus fatores de risco e o papel do colo uterino no processo de parturição.(AU)

Around 15 million preterm births happen globally. In 2015 over 4 million deaths in children under 5 years of age died and preterm birth complications is the leading cause in neonates. Preterm birth is a multiple etiology syndrome, in which various causes converge to a single parturition path. The most important risk factors are multiple gestation and obstetrical history of preterm birth. Uterine cervix is responsible for pregnancy maintenance from conception to birth, and its remodeling process generates effacement, dilation and shortening in a continuum that comprises conditions from cervical insufficiency to preterm birth without membrane disruption. This is a first article, of a series of three, describing preterm birth prevalence, risk factors and uterine cervix role in parturition.(AU)

Comprimento de colo uterino ao ultrassom transvaginal como preditor de risco do parto pré-termo espontâneo / Ultrasound cervical lenght predicting risk for spontaneous preterm birth

O encurtamento do colo uterino é parte da via final comum da parturição seja a termo ou pré-termo. A identificação precoce do comprimento cervical encurtado ao ultrassom transvaginal no segundo trimestre gestacional pode atuar como preditor de risco de prematuridade. Desde a década de 1990, vários estudiosos dedicaram-se a estabelecer parâmetros de referência para as medidas de colo uterino entre 16 e 24 semanas e até hoje o limite mais consensualmente aceito é de 25 mm. Especialistas são favoráveis à triagem universal, mas diretrizes internacionais são controversas quanto à investigação em casos sem antecedente de parto pré-termo, além de diversos estudos apresentarem que há custo-efetividade no rastreamento universal. Neste artigo, discutimos criticamente os parâmetros apresentados por estudos históricos e balizadores de conduta, a custo-efetividade e os guidelines internacionais. Propomos ainda uma reflexão ao pré-natalista, sugerindo a individualização da conduta perante os dados de cada gestante específica.(AU)

Cervical shortening is the final path of parturition, regardless if it is term or preterm. Precocious identification of a shortened cervix by transvaginal ultrasound during the second gestational trimester can act as a risk predictor of prematurity. Since the 1990´s decade, numerous studies established reference ranges for cervical length measurement between 16 to 24 gestational weeks and the most accepted cutoff limit is 25 mm. Experts indicate universal screening, however international guidelines are controversial, even in cases without a history of preterm birth, furthermore, many studies demonstrated cost-effectiveness about the universal screening of cervical length in middle gestation. In this article we discuss historical reference ranges, cost- -effectiveness, and international guidelines. We propose critical thinking and suggest individualized management according to specific characteristics of each patient.(AU)

The role of three-dimensional ultrasound in pregnancies submitted to cerclage.

OBJECTIVE: Cervical cerclage is the standard treatment for cervical incompetence (CI); however, there is still a high risk of preterm birth for women who undergo this treatment. The aim of this study was to longitudinally evaluate findings on two-dimensional transvaginal ultrasonography (2DTVUS) and three-dimensional transvaginal ultrasonography (3DTVUS) that could be related to gestational age at birth. METHODS: A total of 68 pregnant women who were treated with cerclage were evaluated by 2DTVUS and 3DTVUS in the second and third trimesters of pregnancy. Log-rank tests and Cox regression analyses were used to identify significant findings related to gestational age at delivery. RESULTS: A cervical length lower than 281 mm (p= 0.0083), a proximal cervical length lower than 10 mm (p= 0.0151), a cervical volume lower than 18.17 cm3 (p= 0.0152), a vascularization index (VI) under 2.153 (p= 0.0044), and a vascularization-flow index (VFI) under 0.961 (p= 0.0059) in the second trimester were all related to earlier delivery. In the third trimester, a cervical length lower than 20.4 mm (p= 0.0009), a VI over 0.54 (p= 0.0327) and a VFI over 2.275 (p= 0.0479) were all related to earlier delivery. Cervical funnelling in the second and third trimesters and proximal cervical length in the third trimester were not related to gestational age at birth. The COX regression analyses showed that cervical volume in the second trimester; FI and VFI in the third trimester were significantly associated with gestational age at birth. CONCLUSION: In women treated with history-indicated cerclage or ultrasound-indicated cerclage, 2nd trimester cervical volume and 3rd trimester FI and VFI are independent significant sonographic findings associated with time to delivery.

The role of three-dimensional ultrasound in pregnancies submitted to cerclage

SUMMARY OBJECTIVE: Cervical cerclage is the standard treatment for cervical incompetence (CI); however, there is still a high risk of preterm birth for women who undergo this treatment. The aim of this study was to longitudinally evaluate findings on two-dimensional transvaginal ultrasonography (2DTVUS) and three-dimensional transvaginal ultrasonography (3DTVUS) that could be related to gestational age at birth. METHODS: A total of 68 pregnant women who were treated with cerclage were evaluated by 2DTVUS and 3DTVUS in the second and third trimesters of pregnancy. Log-rank tests and Cox regression analyses were used to identify significant findings related to gestational age at delivery. RESULTS: A cervical length lower than 281 mm (p= 0.0083), a proximal cervical length lower than 10 mm (p= 0.0151), a cervical volume lower than 18.17 cm3 (p= 0.0152), a vascularization index (VI) under 2.153 (p= 0.0044), and a vascularization-flow index (VFI) under 0.961 (p= 0.0059) in the second trimester were all related to earlier delivery. In the third trimester, a cervical length lower than 20.4 mm (p= 0.0009), a VI over 0.54 (p= 0.0327) and a VFI over 2.275 (p= 0.0479) were all related to earlier delivery. Cervical funnelling in the second and third trimesters and proximal cervical length in the third trimester were not related to gestational age at birth. The COX regression analyses showed that cervical volume in the second trimester; FI and VFI in the third trimester were significantly associated with gestational age at birth. CONCLUSION: In women treated with history-indicated cerclage or ultrasound-indicated cerclage, 2nd trimester cervical volume and 3rd trimester FI and VFI are independent significant sonographic findings associated with time to delivery.

RESUMO OBJETIVOS: Determinar quais características ultrassonográficas obtidas por meio da ultrassonografia transvaginal bidimensional (USG TV 2D) e tridimensional (USG TV 3D) associam-se ao parto prematuro em gestantes submetidas à cerclagem profilática e terapêutica. MÉTODOS: Sessenta e seis gestantes com feto único submetidas à cerclagem profilática ou terapêutica e acompanhadas no ambulatório de Aborto Habitual da Clínica Obstétrica do Hospital das Clínicas da Faculdade de Medicina da USP, entre 10 de juho de 2012 e 30 de outubro de 2015, foram avaliadas longitudinalmente, por meio das US TV 2D e US TV 3D associadas ao power Doppler para avaliação do VI, FI e VFI, nos três trimestres da gestação. Os resultados foram avaliados em relação ao parto em idade gestacional (IG) menor que 34 semanas e maior ou igual a 34 semanas, assim como em relação à idade do parto como variável contínua. RESULTADOS: O comprimento do colo uterino (CC) e a distância do ponto de cerclagem ao orifício interno do colo uterino (POI) diminuíram de forma significativa entre o segundo e terceiro trimestres da gestação. O CC, o POI e o afunilamento cervical no terceiro trimestre da gestação tiveram relação com a ocorrência de parto em IG<34 semanas. Na análise de regressão de COX, em que a variável de interesse foi o tempo até o parto, o volume do colo uterino no segundo trimestre e o FI e VFI no terceiro trimestre foram significativos. CONCLUSÃO: Foi possível identificar parâmetros ultrassonográficos do colo uterino bi e tridimensionais que se correlacionam com a idade gestacional do parto.

Prematurity prevention: the role of progesterone.

PURPOSE OF REVIEW: This review summarizes the evidence of the effectiveness of progesterone on the rate of preterm birth and evaluates the most recent studies. RECENT FINDINGS: The incidence of preterm delivery is about 7-11% of all pregnant women and preterm birth is one of the most important causes of neonatal morbidity and mortality. Interventions to reduce such complications have been attempted for several years. Most efforts so far have been tertiary interventions, such as treatment with antenatal corticosteroids, tocolytic agents, and antibiotics. Some of these measures have reduced perinatal morbidity and mortality, but the incidence of preterm birth is increasing. Recently, researches have suggested prophylactic progesterone could reduce the preterm birth rate in a select group presenting previous preterm birth and a short cervical length by transvaginal scan at mid-trimester pregnancy. SUMMARY: This review intends to define the current indication for administration of progesterone for pregnant women. On the basis of current knowledge, progesterone should be offered to women with a documented history of a previous spontaneous birth at less than 37 weeks and for those found to have a short cervical length of 15 mm or less. Studies are needed to evaluate progesterone efficacy on other risk factors.