Background

Cesarean scar pregnancies carry a high risk of pregnancy complications including placenta previa with antepartum hemorrhage, placenta accreta spectrum, and uterine rupture.

Objective

To evaluate the development of utero-placental circulation in the first half of pregnancy in ongoing cesarean scar pregnancies and compare it with pregnancies implanted in the lower uterine segment above a previous cesarean delivery scar with no evidence of placenta accreta spectrum at delivery

Study Design

This was a retrospective case-control study conducted in 2 tertiary referral centers. The study group included 27 women who were diagnosed with a live cesarean scar pregnancy in the first trimester of pregnancy and who elected to conservative management. The control group included 27 women diagnosed with an anterior low-lying placenta or placenta previa at 19 to 22 weeks of gestation who had first and early second trimester ultrasound examinations. In both groups, the first ultrasound examination was carried out at 6 to 10 weeks to establish the pregnancy location, viability, and to confirm the gestational age. The utero-placental and intraplacental vasculatures were examined using color Doppler imaging and were described semiquantitatively using a score of 1 to 4. The remaining myometrial thickness was recorded in the study group, whereas the ultrasound features of a previous cesarean delivery scar including the presence of a niche were noted in the controls. Both the cesarean scar pregnancies and the controls had ultrasound examinations at 11 to 14 and 19 to 22 weeks of gestation.

Results

The mean color Doppler imaging vascularity score in the ultrasound examination at 6 to 10 weeks was significantly (P<.001) higher in the cesarean scar pregnancy group than in the controls. High vascularity scores of 3 and 4 were recorded in 20 of 27 (74%) cases of the cesarean scar pregnancy group. There was no vascularity score of 4, and only 3 of 27 (11%) controls had a vascularity score of 3. In 15 of the 27 (55.6%) cesarean scar pregnancies, the residual myometrial thickness was <2 mm. In the ultrasound examination at 11 to 14 weeks, there was no significant difference between the groups in the number of cases with an increased subplacental vascularity. However, 12 cesarean scar pregnancies (44%) presented with 1 or more placental lacunae whereas there was no case with lacunae in the controls. Of the 18 cesarean scar pregnancies that progressed into the third trimester, 10 of them were diagnosed with placenta previa accreta at birth, including 4 creta and 6 increta. In the 19 to 22 weeks ultrasound examination, 8 of the 10 placenta accreta spectrum patients presented with subplacental hypervascularity, out of which 6 showed placental lacunae.

Conclusion

The vascular changes in the utero-placental and intervillous circulations in cesarean scar pregnancies are due to the loss of the normal uterine structure in the scar area and the development of placental tissue in proximity of large diameter arteries of the outer uterine wall. The intensity of these vascular changes, the development of placenta accreta spectrum, and the risk of uterine rupture are probably related to the residual myometrial thickness of the scar defect at the start of pregnancy. A better understanding of the pathophysiology of the utero-placental vascular changes associated with cesarean scar pregnancies should help in identifying those cases that may develop major complications. It will contribute to providing counseling for women about the risks associated with different management strategies.

中文翻译：

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剖宫产瘢痕妊娠子宫胎盘循环的发展：病例对照研究

背景

剖宫产瘢痕妊娠具有很高的妊娠并发症风险，包括前置胎盘伴产前出血、胎盘植入谱和子宫破裂。

客观的

评估正在进行的剖宫产瘢痕妊娠中妊娠前半期子宫胎盘循环的发展，并将其与之前剖宫产瘢痕上方子宫下段植入且分娩时无胎盘植入谱证据的妊娠进行比较

学习规划

这是一项在 2 个三级转诊中心进行的回顾性病例对照研究。该研究组包括 27 名在妊娠前三个月被诊断为活体剖宫产瘢痕妊娠并选择保守治疗的女性。对照组包括 27 名在妊娠 19 至 22 周被诊断为前部低洼胎盘或前置胎盘的女性，她们在妊娠早期和中期进行了超声检查。两组均在 6 至 10 周进行第一次超声检查，以确定妊娠位置、存活率并确定胎龄。使用彩色多普勒成像检查子宫胎盘和胎盘内脉管系统，并使用 1 至 4 分进行半定量描述。剩余的肌层厚度记录在研究组中，而在对照组中注意到先前剖宫产疤痕的超声特征，包括壁龛的存在。剖宫产瘢痕妊娠和对照组均在妊娠 11 至 14 周和 19 至 22 周进行超声检查。

结果

6~10周超声检查平均彩色多普勒成像血管分布评分显着（P<.001) 剖宫产瘢痕妊娠组高于对照组。27 例（74%）剖宫产瘢痕妊娠组病例中有 20 例（74%）记录了 3 和 4 的高血管分布评分。没有 4 分的血管分布，27 名对照者中只有 3 名 (11%) 的血管分布评分为 3。在 27 例剖宫产瘢痕妊娠中，有 15 例 (55.6%) 的残余肌层厚度小于 2 毫米。在 11 至 14 周的超声检查中，胎盘下血管增多的病例数组间无显着差异。然而，12 例剖宫产瘢痕妊娠（44%）出现 1 个或多个胎盘腔隙，而对照组中没有胎盘腔隙。在进展到妊娠晚期的 18 例剖宫产瘢痕妊娠中，有 10 例在出生时被诊断为前置胎盘植入，包括4个creta和6个increta。在19～22周的超声检查中，10例胎盘植入谱患者中有8例出现胎盘下血管过多，其中6例出现胎盘腔隙。

结论

剖宫产瘢痕妊娠中子宫胎盘和绒毛间循环的血管变化是由于瘢痕区域正常子宫结构的丧失以及子宫外壁大直径动脉附近胎盘组织的发育。这些血管变化的强度、胎盘植入谱的发展以及子宫破裂的风险可能与妊娠开始时瘢痕缺损的残余肌层厚度有关。更好地了解与剖宫产瘢痕妊娠相关的子宫胎盘血管变化的病理生理学应该有助于识别可能出现严重并发症的病例。它将有助于为女性提供有关与不同管理策略相关的风险的咨询。