The Overlooked Impact of Lower Uterine Segment Contractions on Second Trimester Cervical Assessment

Introduction: Asymptomatic contractions in the lower uterine segment (LUS) may affect uterocervical angle and cervical length (CL); however, this has never been investigated. Therefore, the aim of this study was to evaluate the effect of LUS contractions on uterocervical angle, CL, and LUS thickness. Materials and Methods: This was a prospective, observational, single-cohort study conducted on 102 asymptomatic singleton pregnancies between 19.0 and 22.6 weeks of gestation. Uterocervical angle and CL were measured by transvaginal ultrasound at two different time points with an interval of at least 20 min. LUS thickness was also measured as an indirect marker of myometrial contraction. A linear and curvilinear regression were performed to explore a potential association between LUS contractions, measured as increments in LUS thickness, and changes in CL and uterocervical angle. Results: The linear regression between changes in LUS thickness and changes in CL showed that LUS contractions impact CL; for every 1-mm increase in LUS thickness, CL increased by 0.909 mm, when the isthmus was included in the CL measurement (R2 = 0.358; β = 0.909; p < 0.001). By contrast, when the isthmus was not included in the measurement, a curvilinear relation between changes in LUS thickness and changes in CL was found (R2 = 0.077; β1 = 0.575, β2 = 0.038; p = 0.018). The relation between changes in uterocervical angle and changes in LUS thickness was not significant. Discussion/Conclusion: LUS contractions can be observed in many asymptomatic women during the second trimester of pregnancy. LUS contractions lead to an increase in CL and LUS thickness, thus impacting ultrasound cervical assessments. These contractions do not affect the uterocervical angle.

[1]  Á. Sepúlveda-Martínez,et al.  The Novel Ultrasonographic Marker of Uterocervical Angle for Prediction of Spontaneous Preterm Birth in Singleton and Twin Pregnancies: A Systematic Review and Meta-Analysis , 2021, Fetal Diagnosis and Therapy.

[2]  I. Karaca,et al.  M-mode Ultrasound Scan as a Potential Alternative Technique for Monitoring Uterine Contractions in Obese Patients , 2021, Reproductive Sciences.

[3]  E. Carreras,et al.  Prospective evaluation of the uterocervical angle as a predictor of spontaneous preterm birth , 2020, Acta obstetricia et gynecologica Scandinavica.

[4]  P. Shah,et al.  Sonographic lower uterine segment thickness after prior cesarean section to predict uterine rupture: A systematic review and meta‐analysis , 2019, Acta obstetricia et gynecologica Scandinavica.

[5]  Jamie Perin,et al.  Global, regional, and national causes of under-5 mortality in 2000–15: an updated systematic analysis with implications for the Sustainable Development Goals , 2016, The Lancet.

[6]  Terry K Koo,et al.  A Guideline of Selecting and Reporting Intraclass Correlation Coefficients for Reliability Research. , 2016, Journal Chiropractic Medicine.

[7]  Takashi Shimizu,et al.  Ultrasound Assessment of Lower Uterine Segment Thickness During Pregnancy, Labour, and the Postpartum Period. , 2016, Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstetrique et gynecologie du Canada : JOGC.

[8]  K. Kagan,et al.  How to measure cervical length , 2015, Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology.

[9]  G. Visser,et al.  Dynamic cervical length changes: Preliminary observations from 30-minute transvaginal ultrasound recordings , 2007, The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians.

[10]  S. Salhan,et al.  Ultrasonographic evaluation of lower uterine segment thickness in patients of previous cesarean section , 2004, International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics.

[11]  S. Gandevia,et al.  Measurement of muscle contraction with ultrasound imaging , 2003, Muscle & nerve.

[12]  D. Twickler,et al.  Pitfalls in ultrasonic cervical length measurement for predicting preterm birth. , 1999, Obstetrics and gynecology.

[13]  E. Thom,et al.  The length of the cervix and the risk of spontaneous premature delivery. National Institute of Child Health and Human Development Maternal Fetal Medicine Unit Network. , 1996, The New England journal of medicine.

[14]  T. Moore.  Patterns of human uterine contractions: implications for clinical practice. , 1995, Seminars in perinatology.

[15]  J. Grisso,et al.  Effects of Physical Activity and Life-Style Factors on Uterine Contraction Frequency , 1992, American journal of perinatology.

[16]  J. Bowie,et al.  Sonographic diagnosis of premature cervical dilatation. Potential pitfall due to lower uterine segment contractions. , 1991, Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine.