A growing body of evidence suggests that the way surgeons close the uterus during cesarean delivery—particularly whether sutures incorporate endometrial tissue—may have significant implications for women's reproductive health for years after childbirth, according to a comprehensive review published in the American Journal of Obstetrics & Gynecology.
Emmanuel Bujold, MD, MSc, of Université Laval, and Roberto Romero, MD, DMedSci, of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, reviewed more than a century of experimental and clinical research. Their conclusion: even small variations in hysterotomy closure technique can alter scar formation and increase the risk of complications ranging from pelvic pain and abnormal bleeding to placenta accreta spectrum and uterine rupture.
Endometrium Exclusion Emerges as Key Principle
Drs. Bujold and Romero found one of the strongest signals in the literature is that including the endometrium—the uterine lining—in the suture line substantially increases the likelihood of poor healing. The principle was first demonstrated in 1961 by Leslie O. S. Poidevin, whose experiments showed defective healing in 78% of uterine incisions closed with endometrium included, compared with 0% when the lining was excluded. In a cohort of 202 women, Poidevin documented scar defects in 73% of endometrium-included closures vs 8% when the endometrium was avoided. All severe defects occurred when the lining had been incorporated.
Researchers believe the mechanism involves incomplete apposition of the inner myometrium, ischemia from tissue strangulation, and implantation of endometrial cells into the scar.
Clinical Consequences Linked to Scar Defects
Scar defects—or "niches"—are associated with several gynecologic and obstetric complications. Reported frequencies cited in the review include:
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Pelvic pain: 11% to 35%
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Postmenstrual spotting: approximately 33% overall; up to about 60% with a niche
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Scar-associated adenomyosis or endometriosis: 0% to 89%
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Cesarean scar pregnancy: around 0.05% to 0.2%
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Placenta accreta spectrum: approximately 0.3% to 6.8%
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Spontaneous preterm birth: 8% to 28%
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Uterine rupture: about 0.1% to 3.4%, with higher risk during trial of labor after cesarean
Dr. Bujold and Dr. Romero's review notes that niche formation appears to mediate many of these outcomes, making closure technique a potentially modifiable factor in long-term maternal health.
Revisiting Single- vs Double-Layer Techniques
Single-layer closure gained popularity in past decades for its speed, but subsequent research identified important distinctions between methods. In a landmark randomized trial in 1992, Hauth et al. found that a single locked layer shortened operative time without increasing short-term complications, and no uterine ruptures were reported in subsequent pregnancies.
Later, however, Bujold and colleagues associated single-layer closure with a higher risk of uterine rupture during trial of labor. Roberge et al. clarified that the risk was specific to locked single-layer techniques that include the endometrium.
Unlocked single-layer closures did not show this same elevated risk pattern, though the data suggest that careful attention to endometrium exclusion remains essential regardless of locking technique.
A 2014 meta-analysis found that double-layer closure results in a thicker residual myometrial layer—by approximately 2.5 to 3 mm—and that unlocked techniques produced thicker scars than locked ones.
Three-Layer Technique Gains Interest
Building on this evidence, Drs. Bujold and Romero described a refined 3-layer hysterotomy repair that emphasizes biologic healing principles, including exclusion of the endometrium and careful restoration of tissue planes.
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The first layer approximates decidua and junctional myometrium while excluding the surface endometrium.
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The second layer reapproximates the bulk of the myometrium to reinforce the uterine wall.
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The third layer approximates superficial myometrium and serosa, smoothing the surface and potentially reducing adhesions.
The authors noted that while the evidence clearly favors endometrium-excluding techniques, data specifically validating the full three-layer method are still developing.
Comparative Studies Support Endometrium Exclusion
Two prospective studies highlighted in the review offer head-to-head comparisons:
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In a study of 137 participants by Hayakawa et al., scar defects occurred in 6% of women whose closure excluded the endometrium, compared with 34% and 16% in two techniques that incorporated it.
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In a randomized trial of 81 women, Roberge et al. reported severe defects in 4% of endometrium-excluding closures vs 20% and 5% in comparison groups. Residual myometrial thickness averaged 6 mm with endometrium exclusion compared with 4 mm to 5 mm using other methods.
A 2025 synthesis by Lino et al. of 4 randomized trials (392 women) found that techniques excluding the endometrium reduced the risk of scar defects by about half.
Other Surgical Factors Matter Too
The review also pointed to several additional technical variables:
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Suture material: Most large studies show no meaningful difference in rupture risk between catgut and synthetic sutures, though some data suggest more defects with catgut.
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Tissue bite size: Evidence from the STITCH trial in abdominal surgery supports the use of smaller, finer bites to improve healing quality.
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Suture direction: In a study of 497 women, parallel-layered closure was associated with fewer defects (8% vs 16%) and fewer gynecologic symptoms. Parallel suture placement may distribute tension more evenly along the incision and reduce localized stress and ischemia compared with perpendicular orientation.
A Practical Framework: REPAIR
To guide clinical practice, Drs. Bujold and Romero proposed the mnemonic REPAIR:
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Restoring anatomy
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Excluding endometrium or decidua
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Preserving tissue integrity
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Approximating tissue layers
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Improving perfusion with unlocked, tension-free sutures
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Reducing dead space
They argued that meticulous technique—not operative speed—should drive surgical decision-making, given the long-term implications for maternal health.
Special Circumstances and Future Needs
The 3-layer technique may be most feasible in cesareans performed before or early in labor, when the lower uterine segment is still structurally distinct.
During advanced labor, when the segment becomes extremely thin and may blend into cervical tissue, modifications may be required. One randomized trial suggests that placing the incision approximately 2 cm above the vesicouterine fold may decrease the likelihood of scar defects.
The authors emphasized substantial knowledge gaps, including the optimal closure approach for second-stage cesarean deliveries. They called for clinical trials focused on outcomes that matter to patients—uterine integrity, reproductive performance, and long-term gynecologic health.
"Cesarean delivery has lasting consequences for mothers and their families," the authors wrote. "Because of its global frequency and lifelong impact, research aimed at optimizing uterine closure should be recognized as an immediate public health priority."
Disclosures can be found in the published review.