Comparison of the lower uterine segment in pregnant women with and without previous cesarean section in 3 T MRI

Predicting Uterine Rupture Risk Using Lower Uterine Segment Measurement During Pregnancy With Cesarean History: How Reliable Is It? A Review

Importance

Uterine rupture during labor is a calamitous event that can result in maternal/neonatal morbidity/mortality. Lower uterine segment (LUS) thickness measurement is a proposed method to determine the risk factor of uterine rupture in women undergoing trial of labor after cesarean. Does this measurement predict uterine rupture risk?

Objectives

This review examines current evidence to determine if a thin LUS ultrasound diagnosis during pregnancy with prior cesarean delivery(s) can reliably predict uterine rupture risk while attempting vaginal birth after cesarean (VBAC).

Evidence Acquisition

Electronic databases (PubMed and CINAHL) were searched with one limitation of abstracts in English. Search terms used were "lower uterine segment" AND "risk(s)" AND "rupture" OR "dehiscence.

Results

After reviewing 164 identified articles, 15 were used in this review. Of the studies including LUS thickness measurement, notable differences were found: gestational age at time of measurement, full thickness measurement versus myometrial thickness, number of sonographers involved, ultrasound technique (transabdominal vs transvaginal), and blinding. Other factors influencing LUS thickness include fetal weight, amniotic fluid volume, and gestational age. The most recent systematic review and meta-analysis suggests that an LUS > 3.65 mm should be safe for a VBAC, 2-3.65 mm is probably safe, and <2 mm identifies a patient at higher risk for uterine rupture/dehiscence.

Conclusions

Study heterogeneity, absence of an agreed upon thickness threshold, poor correlation between ultrasound and MRI measurements, or physical cesarean measurements currently make VBAC uterine rupture risk prediction uncertain.

Relevance

Our aim is to analyze existing literature to determine if evidence supports LUS measurement in women undergoing VBAC after cesarean to determine risk of uterine rupture.

Comparison of Diagnostic Efficacy among Transvaginal Sonography, Transabdominal Sonography, and 3.0 T Magnetic Resonance Imaging in Early Cesarean Scar Pregnancy

Objective

To compare the diagnostic efficacy among transvaginal sonography (TVS), transabdominal sonography (TAS), and 3.0 T magnetic resonance imaging (MRI) in early cesarean scar pregnancy (CSP).

Methods

The clinical data of 65 patients initially diagnosed with CSP in our hospital from November 2019 to November 2020 were selected for the retrospective analysis, and all patients received TVS, TAS, and 3.0 T MRI. Taking the pathological findings as the “gold standard”, the diagnostic efficacy of different diagnostic modalities in early CSP was compared.

Results

In terms of the AUC value, the result was 3.0 T MRI > TVS > TAS, and among the three diagnosis methods, 3.0 T MRI had the highest diagnostic specificity, and TVS and 3.0 T MRI had the highest sensitivity; other than intragestational hemorrhage, the detection rates of other signs of disease by TVS and TAS were significantly higher than 3.0 T MRI (P < 0.05).

Conclusion

3.0 T MRI has better diagnostic efficacy in early CSP than TVS and TAS, while TVS and TAS work better in diagnosing uterine bleeding, plumule, yolk sac, and fetal heartbeat than 3.0 T MRI. The results are more beneficial to the guidance on selecting treatment modalities.

The Intraoperative Median Effective Dose of Oxytocin for Preventing Uterine Atony in Parturients with a Prior History of Caesarean Delivery

BACKGROUND AND OBJECTIVE

While oxytocin is commonly used for the prevention of uterine atony, its pharmacology may be affected by a prior history of caesarean delivery. The objective of this study was to determine the 50% effective dose (ED₅₀) of bolus oxytocin after caesarean delivery in parturients with and without prior caesarean delivery.

METHODS

This was a parallel-group, double-blind, dose-response study using Dixon's up-and-down sequential allocation method to estimate the ED₅₀ of bolus-administered oxytocin in parturients having caesarean delivery under combined spinal-epidural anaesthesia (CSE). Twenty-seven parturients with a history of prior caesarean delivery (With-PCD group) and 26 parturients with no such history (Without-PCD group) were enrolled. Oxytocin was administered as an intravenous bolus at a starting dose of 0.5 units, which was then increased or decreased by 0.25 units at a time. Uterine tone was assessed by the obstetrician as either 'adequate' or 'inadequate' 3 min after delivery of the fetus. Adverse effects, administration of additional uterotonic agents, and estimated blood loss were recorded.

RESULTS

The ED₅₀ of oxytocin was greater in the With-PCD group than in the Without-PCD group (0.95 units [95% CI 0.82-1.08] vs. 0.55 units [95% CI 0.38-0.73], P < 0.001). The overall incidence of adverse effects was higher in the With-PCD group than in the Without-PCD group (33.3% vs. 7.7%, P = 0.02).

CONCLUSION

The initial bolus dose of oxytocin needed to prevent uterine atony was higher in parturients with prior caesarean delivery than in parturients without prior caesarean delivery. Uterine scarring may contribute to the increased oxytocin requirements of the former group.

TRIAL REGISTRATION NUMBER

ChiCTR1900023474; investigator: Wei CN; date of registration: 30 May 2019.

The diagnostic value of 3.0T MRI in cesarean scar pregnancy

OBJECTIVE

The purpose was to evaluate the diagnostic value of 3.0T MRI in cesarean scar pregnancy (CSP).

METHODS

56 patients with suspected CSP treated in our hospital from August 2018 to July 2020 were recruited as the study cohort and diagnosed using ultrasound and 3.0T MRI. With the pathological examination results as the gold standard and the ultrasound examination results as a comparison, the diagnostic value of 3.0T MRI was evaluated according to the diagnostic accuracy, sensitivity, specificity, and positive and negative misdiagnosis rates, etc. Results: The pathological examination showed that 33 patients were positive for CSP but the other 23 were negative. The accuracy, sensitivity, and specificity of 3.0T MRI in the CSP diagnoses were significantly higher than the accuracy, sensitivity, and specificity of the ultrasound diagnoses (P<0.05), and the positive and negative misdiagnosis rates were significantly lower than the misdiagnosis rates of the ultrasound diagnosis (P<0.05). Moreover, the images from two patients showed that 3.0T MRI can provide clear images of the patients' lesion locations.

CONCLUSION

Compared with ultrasound diagnoses, 3.0TMRI has significant advantages in diagnosing CSP and has a high clinical value.

Uterine Dehiscence and Subsequent Pregnancy Management: A Review of the Literature

Importance

Uterine dehiscence is a separation of the uterine musculature with intact uterine serosa. Uterine dehiscence can be encountered at the time of cesarean delivery, be suspected on obstetric ultrasound, or be diagnosed in between pregnancies. Management is a conundrum for obstetricians, regardless of timing of onset.

Evidence Acquisition

A literature search was undertaken by our research librarian using the search engines PubMed, CINAHL, and Web of Science. The search term used was "uterine dehiscence." The search was limited to the English language, and there was no limit on the years searched.

Results

The search identified 152 articles, 32 of which are the basis for this review. Risk factors, treatment, and management in subsequent pregnancies are discussed. The number of prior cesarean deliveries is the greatest risk factor for uterine dehiscence. Unrepaired uterine dehiscence can cause symptoms outside of pregnancies and may require repair for alleviation of these symptoms. Dehiscence should also be repaired prior to subsequent pregnancies.

Conclusion and Relevance

Planned delivery prior to the onset of labor with careful monitoring of maternal symptoms is the preferred management strategy of women with prior uterine dehiscence. Careful attention should be paid to the lower uterine segment thickness when ultrasonography is performed in women with prior cesarean delivery.

Relevance Statement

An evidence-based review of uterine dehiscence in pregnancy and how to manage subsequent pregnancies following uterine dehiscence.

Special Report of the Society for Maternal-Fetal Medicine Placenta Accreta Spectrum Ultrasound Marker Task Force: Consensus on definition of markers and approach to the ultrasound examination in pregnancies at risk for placenta accreta spectrum

Placenta accreta spectrum includes the full range of abnormal placental attachment to the uterus or other structures, encompassing placenta accreta, placenta increta, placenta percreta, morbidly adherent placenta, and invasive placentation. The incidence of placenta accreta spectrum has increased in recent years, largely driven by increasing rates of cesarean delivery. Prenatal detection of placenta accreta spectrum is primarily made by ultrasound and is important to reduce maternal morbidity associated with the condition. Despite a large body of research on various placenta accreta spectrum ultrasound markers and their screening performance, inconsistencies in the literature persist. In response to the need for standardizing the definitions of placenta accreta spectrum markers and the approach to the ultrasound examination, the Society for Maternal-Fetal Medicine convened a task force with representatives from the American Institute of Ultrasound in Medicine, the American College of Obstetricians and Gynecologists, the American College of Radiology, the International Society of Ultrasound in Obstetrics and Gynecology, the Society for Radiologists in Ultrasound, the American Registry for Diagnostic Medical Sonography, and the Gottesfeld-Hohler Memorial Ultrasound Foundation. The goals of the task force were to assess placenta accreta spectrum sonographic markers on the basis of available data and expert consensus, provide a standardized approach to the prenatal ultrasound evaluation of the uterus and placenta in pregnancies at risk of placenta accreta spectrum, and identify research gaps in the field. This manuscript provides information on the Placenta Accreta Spectrum Task Force process and findings.