Prevalence and Evaluation of Cesarean Scar Niche

Although the risk of scar niche formation increases with multiple cesarean deliveries, it is important to recognize that a niche can also develop after a single cesarean delivery, says a study published in The American Journal of Obstetrics and Gynecology.¹

The objective of this cross-sectional study was to determine the prevalence and dimensions of internal, external, and bidirectional scar niches in 200 women with a past history of cesarean deliveries who had undergone hysterectomy due to abnormal uterine bleeding (AUB) between December 2021 to November 2023. Their mean age was 48.19 years; 30% had undergone only one cesarean delivery. The niches were detected both via preoperative transvaginal ultrasound (TVS) and gross specimens from hysterectomy. The dimensions assessed were height, residual myometrial thickness, and adjacent myometrial thickness. 

Analysis revealed that niches were detected in 83.5% of patients using sonography, while 91% were identified in uterine tissue samples obtained through hysterectomy. Internal niches were most commonly detected, while external niches were found only in hysterectomy samples (4%) but were not detected by ultrasound. 23.3% of patients with one cesarean delivery had internal niches.

Significant differences were noted in residual myometrial thickness and adjacent myometrial thickness between ultrasound reports and tissue samples. Discrepancies in measurements were observed. The residual myometrial thickness was 7.68 mm in TVS and 4.28 mm in tissue samples. The adjacent myometrial thickness was 17.08 mm in TVS and 16 mm in tissue samples.

 This study emphasizes the need for scar precise evaluation of niches in patients with a history of cesarean delivery and demonstrates disparities in diagnostic methods. It draws attention to the significance of assessing external and bidirectional niches, in addition to internal niches, as these can lead to reduced residual myometrial thickness and increase the risk of complications in future pregnancies such as ectopic scar pregnancies, placenta accreta and even uterine rupture.

Source:. Am J Obstet Gynecol. 2025 Apr;232(4):373.e1-373.e10. doi: 10.1016/j.ajog.2024.10.010.