CC BY 4.0 · Rev Bras Ginecol Obstet 2019; 41(10): 581-587
DOI: 10.1055/s-0039-1697986
Original Article
Thieme Revinter Publicações Ltda Rio de Janeiro, Brazil

Do We Know How to Avoid OASIs in Non-Supine Birth Positions? A Retrospective Cohort Analysis

Sabemos como evitar as LOEAs em posições de parto não supinas? Uma análise de coorte retrospectiva
1   Department of Obstetrics and Gynecology, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, MG, Brazil
1   Department of Obstetrics and Gynecology, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, MG, Brazil
Anna Laura Freitas Vianini
1   Department of Obstetrics and Gynecology, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, MG, Brazil
Marilene Vale Castro Monteiro
1   Department of Obstetrics and Gynecology, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, MG, Brazil
Regina Amélia Lopes Pessoa Aguiar
1   Department of Obstetrics and Gynecology, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, MG, Brazil
› Author Affiliations
Further Information

Publication History

16 April 2019

26 June 2019

Publication Date:
28 October 2019 (online)


Objective To evaluate the association between the upright and supine maternal positions for birth and the incidence of obstetric anal sphincter injuries (OASIs).

Methods Retrospective cohort study analyzed the data of 1,728 pregnant women who vaginally delivered live single cephalic newborns with a birth weight of 2,500 g. Multiple regression analyses were used to investigate the effect of the supine and upright positions on the incidence of OASIs after adjusting for risk factors and obstetric interventions.

Results In total, 239 (13.8%) births occurred in upright positions, and 1,489 (86.2%) in supine positions. Grade-III lacerations occurred in 43 (2.5%) patients, and grade-IV lacerations occurred in 3 (0.2%) women. Supine positions had a significant protective effect against severe lacerations, odds ratio [95% confidence interval]: 0,47 [0.22–0.99], adjusted for the use of forceps 4.80 [2.15–10.70], nulliparity 2.86 [1.44–5.69], and birth weight 3.30 [1.56–7.00]. Anesthesia (p < 0.070), oxytocin augmentation (p < 0.228), shoulder dystocia (p < 0.670), and episiotomy (p < 0.559) were not associated with the incidence of severe lacerations.

Conclusion Upright birth positions were not associated with a lower rate of perineal tears. The interpretation of the findings regarding these positions raised doubts about perineal protection that are still unanswered.


Objetivo Avaliar a associação entre as posições maternas verticais e supinas ao nascimento e a taxa de incidência de lesões obstétricas do esfíncter anal (LOEAs).

Métodos Estudo coorte retrospectivo que analisou os dados de 1.728 gestantes que tiveram parto vaginal cefálico simples com peso ao nascer de 2.500 g. Análises de regressão múltipla foram usadas para investigar o efeito de posições supinas ou verticais sobre a taxa de incidência de LOEAs após o ajuste para fatores de risco e intervenções obstétricas.

Resultados No total, 239 (13,8%) nascimentos ocorreram nas posições verticais, e 1,489 (86,2%), nas posições supinas. Lacerações graves de grau III ocorreram em 43 (2,5%) pacientes, e de grau IV, em 3 (0,2%) mulheres. As posições supinas tiveram um efeito protetor significativo contra lacerações graves, razão de probabilidades [Intervalo de Confiança de 95%]: 0,47 [0.22–0.99], ajustado para o uso de Fórceps 4.80 [2.15–10.70], nuliparidade 2.86 [1.44–5.69], e peso ao nascer 3.30 [1.56–7.00]. Anestesia (p < 0.070), aumento de ocitocina (p < 0.228), distocia de ombro (p < 0.670), e episiotomia (p < 0.559) não estiveram associados à incidência de laceração grave.

Conclusão As posições de parto verticais não estiveram associadas a uma menor taxa de ruptura perineal. A interpretação dos achados referentes a essas posições levantou dúvidas sobre a proteção perineal que ainda aguardam respostas.


All authors contributed with the project and the interpretation of data, the writing of the article, the critical review of the intellectual content, and with the final approval of the version to be published.

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