Comparison of the primary cesarean hysterotomy scars after single- and double-layer interrupted closure SOROMON KATAOKA, FUMIE TANUMA, YUTAKA IWAKI, KURUMI IWAKI, TAKERU FUJII & TOSHIO FUJIMOTO Department of Obstetrics and Gynecology, Hakodate Central General Hospital, Hakodate, Japan ACTA Obstetricia et Gynecologica Scandinavica Journal Club December 2016 Edited by Francesco D’Antonio

Background Caesarean section (CS) is one of the most common surgical procedures performed worldwide. CS may be associated with several short and long-term maternal adverse outcomes such as haemorrhage, hysterectomy and abnormally invasive placenta. Formation of uterine niches at the site of CS represents the main risk factor for uterine rupture, placenta accreta, cesarean scar pregnancy in a future pregnancy. It has still to be ascertained whether suture techniques can affect niche development.

Aim of the study To analyze the effect of single and double-layer interrupted closure of hysterotomy incisions during primary cesarean section on the formation of uterine niches

Methodology Study design: Prospective cohort study. Inclusion criteria: Women undergoing primary caesarean section (pCS) with a transverse lower uterine segment incision at the Department of Obstetrics and Gynecology of Hakodate Central General Hospital, Japan between 2011 and 2014. Exclusion criteria: Myomas around the site of the CS scar, cervical cancer, ovarian cancer, and pelvic inflammatory disease. Intervention: Saline contrast sonohysterosonography (SCSH). Outcomes explores: Niche severity according to the type of suture.

Surgical techniques (a) Single-layer interrupted suture (b) double-layer interrupted suture

Saline contrast sonohysterography Niche severity was expressed as a ratio of the niche depth to the sum of the niche depth (N) and residual myometrium thickness (M) [i.e. niche ratio = N / N + M)]

Results (1) Flowchart of the study cohorts that underwent (a) single-layer closure and (b) double-layer closure.

Results (2) Until the niche ratio was 0.4, there was no significant difference between the two groups Niche ratio ≥0.4 and 0.5 significantly higher in women with single layer repair No demographic or obstetric differences between the single and double-layer groups

Results (2)   Univariate analysis OR 95% CI p value Forward stepwise multivariate regression Single-layer suture 4.64 1.50 14.42 0.008 5.59 1.71 18.28 0.004 Maternal age 1.02 0.92 1.13 0.71 Gestational age 0.91 1.41 0.27 Plural fetal pregnancy 3.20 0.93 11.01 0.07 Primipara 0.76 0.25 2.32 0.63 Preeclampsia 0.36 0.05 2.82 0.33 Cervix dilatation ≥ 5 cm 1.56 0.41 5.91 0.51 Retroflexion of the uterus 1.78 0.56 5.63 Blood loss per 100 mL 1.10 1.17 0.009 1.11 1.03 1.19 0.005 Risk of a niche ratio ≥0.4 was associated with the closure technique (OR 4.64; 95% CI 1.50–14.42) and blood loss per 100 mL (OR 1.10; 95% CI 1.02–1.17) Five-fold increase in the odds of a large niche formation (i.e. a niche ratio ≥0.4) when the single-suture technique was used (OR 5.59; 95% CI 1.71–18.28) Blood loss per 100 mL (OR 1.11; 95% CI 1.03–1.19) was independently associated with a niche ratio ≥0.4

Limitations Single center study (low external validity) Small sample size Lack of randomization Examiners not blinded to the results Different time at enrollment There is still a need for more objective evidence on which suturing technique to use during CS in order to reduce short and long term complications

Research agenda Need for randomized controlled studies with: Larger sample size Long-term follow-up Evaluation of intra- and intra-observer variability in assessing severity of the niche Association with different clinical outcomes

Conclusion Single-layer closure may be associated with an increased risk of larger niches (niche ratio ≥0.4), although it may not increase the overall frequency of niche formation