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Farràs A, Catalán S, Casellas A, Higueras T, Calero I, Goya M, Maiz N, Brik M, Carreras E. Real-time ultrasound demonstration of uterine isthmus contractions during pregnancy. Am J Obstet Gynecol 2024; 230:89.e1-89.e12. [PMID: 37481152 DOI: 10.1016/j.ajog.2023.07.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 07/05/2023] [Accepted: 07/14/2023] [Indexed: 07/24/2023]
Abstract
BACKGROUND Asymptomatic isthmic contractions are a frequent physiological phenomenon in pregnancy, sometimes triggered by bladder voiding. They can interfere with proper cervical length assessment and may lead to false images of placenta previa. However, there is limited research on the prevalence and characteristics of these contractions. OBJECTIVE This study aimed to determine the prevalence and characteristics of isthmic contractions after bladder voiding in the second trimester of pregnancy, to evaluate their effect on cervical length assessment, and to propose a new method for the objective assessment of the presence and intensity of isthmic contractions. STUDY DESIGN In this prospective observational study, long videos of the uterine cervix were recorded in 30 singleton pregnancies during the second trimester of pregnancy after bladder voiding. Isthmic length and cervicoisthmic length changes were assessed over time. The isthmic length was measured using a new approach, which involved calculating the distance from the base of the cervix to the internal os, including the isthmus. RESULTS Isthmic contractions were observed in 43% of pregnant women (95% confidence interval, 26%-62%) after bladder voiding. The median time for complete isthmus relaxation was 19.7 minutes (95% confidence interval, 15.0 to not available). No substantial differences in maternal characteristics were found between individuals with and without contractions. The proposed method for measuring isthmic length provided an objective assessment of the presence and intensity of isthmic contractions. A cutoff of 18 mm in isthmic length allowed for the distinction of pregnant women presenting a contraction. In addition, the study identified a characteristic undulatory pattern in the relaxation of the isthmus in half of the cases with contractions. CONCLUSION Isthmic contractions are a common occurrence after bladder voiding in the second trimester of pregnancy and may interfere with proper cervical length assessment. We recommend performing cervical assessment at least 20 minutes after bladder voiding to reduce the risk of bias in cervical length measurement and to avoid false images of placenta previa. The new method for measuring isthmic length provides an objective way to assess the presence and intensity of isthmic contractions. Further research is needed to understand the role of isthmic contractions in the physiology of pregnancy and birth.
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Affiliation(s)
- Alba Farràs
- Maternal and Fetal Medicine Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Maternal and Fetal Medicine Group, Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain.
| | - Sara Catalán
- Departament de Pediatria, Obstetrícia i Ginecologia i Medicina Preventiva i Salut Pública. Universitat Autònoma de Barcelona, Bellaterra, Spain; Maternal and Fetal Medicine Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Maternal and Fetal Medicine Group, Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain
| | - Alba Casellas
- Maternal and Fetal Medicine Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Maternal and Fetal Medicine Group, Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain
| | - Teresa Higueras
- Maternal and Fetal Medicine Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Maternal and Fetal Medicine Group, Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain; Departament de Pediatria, Obstetrícia i Ginecologia i Medicina Preventiva i Salut Pública. Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Inés Calero
- Maternal and Fetal Medicine Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Maternal and Fetal Medicine Group, Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain; Departament de Pediatria, Obstetrícia i Ginecologia i Medicina Preventiva i Salut Pública. Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - María Goya
- Maternal and Fetal Medicine Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Maternal and Fetal Medicine Group, Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain; Departament de Pediatria, Obstetrícia i Ginecologia i Medicina Preventiva i Salut Pública. Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Nerea Maiz
- Maternal and Fetal Medicine Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Maternal and Fetal Medicine Group, Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain; Departament de Pediatria, Obstetrícia i Ginecologia i Medicina Preventiva i Salut Pública. Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Maia Brik
- Maternal and Fetal Medicine Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Maternal and Fetal Medicine Group, Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain
| | - Elena Carreras
- Maternal and Fetal Medicine Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Maternal and Fetal Medicine Group, Vall d'Hebron Institut de Recerca (VHIR), Barcelona, Spain; Departament de Pediatria, Obstetrícia i Ginecologia i Medicina Preventiva i Salut Pública. Universitat Autònoma de Barcelona, Bellaterra, Spain
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Abstract
Background Work in voiding (WIV) of the bladder may be used to evaluate bladder status throughout urination, not just at a single time point. Few studies, however, have assessed WIV due to the complexity of the calculations. We have developed a method of calculating work capacity of the bladder while voiding and analyzed the associations of bladder work parameters with bladder contractile function and bladder outlet obstruction (BOO). Methods The study retrospectively evaluated 160 males, aged >40 years and with a detrusor pressure at maximal flow rate (PdetQmax) of ≥40 cmH2O, who underwent urodynamic testing. WIV was calculated using the bladder power integration method; WIV per second (WIV/t) and WIV per liter urine voided (WIV/v) were also calculated. The relationships between these work capacity parameters and PdetQmax and AG number were determined using linear-by-linear association tests, and relationships between work capacity parameters and BOO grade were investigated using Spearman’s association test. Results Mean WIV was 1.15±0.78 J, mean WIV/t was 22.95±14.45 milliWatt, and mean WIV/v was 5.59±2.32 J/L. WIV/v showed significant positive associations with PdetQmax (r=0.845, P=0.000), AG number (r=0.814, P=0.000), and Schafer class (r=0.726, P=0.000). Conversely, WIV and WIV/t showed no associations with PdetQmax or AG number. In patients with BOO (Schafer class > II), WIV/v correlated positively with increasing BOO grade. Conclusions WIV can be calculated from simple urodynamic parameters using the bladder power integration method. WIV/v may be a marker of both bladder contractile function and BOO.
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