Strengths and limitations
The strengths of our study are that it is a retrospective, cohort study matched with the degree of cervical dilation in ECC technology in twin pregnancy, which undertook a subgroup analysis for cervical dilation ≥ 3cm and < 3cm. There are no prior dedicated retrospective, cohort matched studies in this population. Our study adds to the current limited literature on ECC technique in twin pregnancies. Despite the small sample size, we were able to show a significant benefit of this novel technique in twin pregnancies with cervical dilation 1-6cm. Furthermore, our study proposed the potential benefit of this novel technique even in women with cervical dilation ≥3cm and prolapsed membranes, in whom had a high chance of sPTB before 28 weeks and we first to suggest that ECC placement may be extended to 26 weeks of gestation in twins. Also, our study does have some limitations. Firstly, because of the retrospective nature of this study, selection bias was inevitable despite our attempts to reduce this by matching one-on-one with controls. Secondly, there could be a potential concern that the patients considered subjectively to have a higher risk of PTB tend to receive combined McDonald-Shirodkar procedure, resulting in possible selection bias. However, the clinical characteristics between the two groups were similar, suggesting that selection bias was minimal. Due to these limitations, future randomized control studies with large samples are warranted to evaluate the efficacy of each treatment and confirm our findings.
Conclusions: In addition, we suggested that ECC placement may be extended to 26 weeks of gestation in twin pregnancy. ECC performed with the combined McDonald-Shirodkar methord in twins with cervical dilation 1-6 cm may reduce the rate of sPTB and improve perinatal and neonatal outcomes compared with McDonald procedure, especially for twins with cervical dilation of 3-6 cm and prolapsed membranes.