Interactions between ultrasonographic cervical length and placenta accreta spectrum on severe postpartum hemorrhage in women with placenta previa

Abstract Objective To explore the interactions between cervical length (CL) and placenta accreta spectrum (PAS) on severe postpartum hemorrhage (SPPH) in patients with placenta previa. Methods A retrospective case–control study was conducted at four medical centers in China, and 588 patients with placenta previa were included. The logistic regression analysis and restricted cubic splines (RCS) were used to evaluate the association between CL and SPPH. Furthermore, the joint effect of CL and PAS on SPPH was assessed, and the additive and multiplicative interactions were calculated. Results After adjusting for potential confounders, the negative linear dose–response relationship was confirmed by RCS, and the change of odds ratio (OR) was more significant when CL was 2.5 cm or less. The risk of SPPH was significantly higher when CL of 2.5 cm or less co‐existed with placenta increta/percreta than when CL of 2.5 cm less, or placenta increta/percreta existed alone (adjusted OR [aOR] CL ≤2.5cm&placenta accreta/non‐PAS 3.40, 95% confidence interval [CI] 1.37–8.45; aOR placenta increta/percreta&CL >2.5cm 4.75, 95% CI 3.03–7.47; aOR CL ≤2.5cm&placenta increta/percreta 14.51, 95% CI 6.08–34.64), and there might be additive interaction between CL and placenta increta/percreta on SPPH (attributable proportion due to interaction 50.7%, 95% CI 6.1%–95.3%). Conclusion If CL was routinely performed during PAS evaluation, the increased OR of short CL and PAS could allow better patient preparation through counseling.