True Knot Research Articles

Estimating umbilical cord flow resistance from measurements of the whole cord

Measuring umbilical blood pressure in utero is challenging and for this reason non-invasive methods are required. However, the total vessel blood pressure drop can be estimated using numerical and empirical results by studying the mechanics of fluids in coiled and straight tubes. Two key findings emerge from such an analysis. Firstly, the total pressure drop along a vessel at a given blood flow-rate depends on both the tightness of the coils and the total cord length. Relatively short and straight cords exhibit low pressure, while long, tightly coiled cords with large width exhibit high pressure. It follows that an estimate of the pressure requires three measurements: the full cord length, its average width and number of coils. Using this result we propose two prototype indices for clinical testing that estimate umbilical cord flow resistance. The umbilical pressure index (PX) and flow index (QX) quantify the deviation of a cord geometry from defined typical conditions by considering the steady pressure drop and flow-rate, respectively. These indices can be quickly calculated, and require only a single additional measurement to the conventional umbilical coiling index (UCI); namely the cord coiling width. Unlike the UCI, these indices are derived from blood-flow properties and provide a measure of the relative flow-resistance inherent to a cord geometry. Furthermore, the pressure index can be applied to irregularities, including loose true knots, which we show must be accounted for.

Umbilical cord characteristics and their association with adverse pregnancy outcomes: A systematic review and meta-analysis.

Current data on the role of the umbilical cord in pregnancy complications are conflicting; estimates of the proportion of stillbirths due to cord problems range from 3.4 to 26.7%. A systematic review and meta-analysis were undertaken to determine which umbilical cord abnormalities are associated with stillbirth and related adverse pregnancy outcomes. MEDLINE, EMBASE, CINAHL and Google Scholar were searched from 1960 to present day. Reference lists of included studies and grey literature were also searched. Cohort, cross-sectional, or case-control studies of singleton pregnancies after 20 weeks' gestation that reported the frequency of umbilical cord characteristics or cord abnormalities and their relationship to stillbirth or other adverse outcomes were included. Quality of included studies was assessed using NIH quality assessment tools. Analyses were performed in STATA. This review included 145 studies. Nuchal cords were present in 22% of births (95% CI 19, 25); multiple loops of cord were present in 4% (95% CI 3, 5) and true knots of the cord in 1% (95% CI 0, 1) of births. There was no evidence for an association between stillbirth and any nuchal cord (OR 1.11, 95% CI 0.62, 1.98). Comparing multiple loops of nuchal cord to single loops or no loop gave an OR of 2.36 (95% CI 0.99, 5.62). We were not able to look at the effect of tight or loose nuchal loops. The likelihood of stillbirth was significantly higher with a true cord knot (OR 4.65, 95% CI 2.09, 10.37). True umbilical cord knots are associated with increased risk of stillbirth; the incidence of stillbirth is higher with multiple nuchal loops compared to single nuchal cords. No studies reported the combined effects of multiple umbilical cord abnormalities. Our analyses suggest specific avenues for future research.

Complex Twisted Knots of Umbilical Cord in a Monochorionic-Diamniotic Twin Gestation: A Case Report

Background: True knots and tight loops of umbilical cord can cause serious fetal complications in monochorionic-monoamniotic twins but are usually unexpected in Monochorionic-diamniotic twins because of the presence of the intertwin membrane. This report presents a case of monochorionic-diamniotic twin gestation with a complex cord knots. Case report: A 31-year-old G2Ab1 with monochorionic-diamniotic twin pregnancy in the gestational age of 30 weeks presented with ruptured membrane since 3weeks before delivery. At the delivery time, multiple umbilical cord knots was found. Conclusion: Premature ruptured membrane can cause septostomy of the intertwin membrane, multiple umbilical cord knots and its complications. Therefore, these cases should be considered for evaluation of the presence of intertwin membrane and umbilical cord knots in each sonography examination. [GMJ.2020;9:e1878]

Current Perspectives of Prenatal Sonographic Diagnosis and Clinical Management Challenges of Nuchal Cord(s).

Umbilical cord accidents preceding labor are uncommon. In contrast, nuchal cords are a very common finding at delivery, with reported incidences of a single nuchal cord of approximately between 20% and 35% of all singleton deliveries at term. Multiple loops occur less frequently, with reported incidence rates inverse to the number of nuchal cords involved. Rare cases of up to 10 loops of nuchal cord have been reported. While true knots of the umbilical cord have been associated with a 4–10-fold increased risk of stillbirth, nuchal cord(s) are most often noted at delivery of non-hypoxic non-acidotic newborns, without any evidence of subsequent adverse neonatal outcome. Prior to ultrasound, nuchal cords were suspected clinically following subtle (spontaneous or evoked) electronic fetal heart rate changes. Prenatal sonographic diagnosis, initially limited to real-time gray-scale ultrasound, currently entails additional sonographic modalities, including color Doppler, power Doppler, and three-dimensional sonography, which have enabled increasingly more accurate prenatal sonographic diagnoses of nuchal cord(s). In contrast to true knots of the umbilical cord (which are often missed at sonography, reflecting the inability to visualize the entire umbilical cord, and hence are often incidental findings at delivery), nuchal cord(s), reflecting their well-defined and sonographically accessible anatomical location (the fetal neck), lend themselves with relative ease to prenatal sonographic diagnosis, with increasingly high sensitivity and specificity rates. While current literature supports that single (and possibly double) nuchal cords are not associated with increased adverse perinatal outcome, emerging literature suggests that cases of ≥3 loops of nuchal cords or in the presence of a coexisting true knot of the umbilicus may be associated with an increased risk of stillbirth or compromised neonatal status at delivery. This commentary will address current perspectives of prenatal sonographic diagnosis and clinical management challenges associated with nuchal cord(s) in singleton pregnancies.

Current Perspectives of Prenatal Sonographic Diagnosis and Clinical Management Challenges of True Knot of the Umbilical Cord.

Umbilical cord accidents preceding labor are rare. Single and multiple nuchal cords, and true knot(s) of the umbilical cord, are often incidental findings noted at delivery of non-hypoxic non-acidotic newborns without any evidence of subsequent adverse neonatal outcome. In contrast to single nuchal cords, true knots of the umbilical cord, which occur in between 0.04% and 3% of all deliveries, have been associated with a reported 4 to 10 fold increased risk of stillbirth. First reported with real-time ultrasound, current widespread application of color Doppler, power Doppler and three-dimension sonography, has enabled increasingly more accurate prenatal sonographic diagnoses of true knot(s) of the umbilical cord. Reflecting the inability to visualize the entire umbilical cord at prenatal ultrasound assessment, despite detailed second and third-trimester scanning, many occurrences of incidental true knot of the umbilical cord remain undetected and are noted only at delivery. Although prenatal sonographic diagnostic accuracy is increasing, false positive sonographic diagnosis of true knot of the umbilical cord cannot be ruled out with certainty, and must continue to be considered clinically. Notwithstanding the inability to diagnose all true knots, currently there is a clear absence of clinical management guidelines by governing bodies regarding patients in whom prenatal sonographic diagnosis of true knot(s) of the umbilical cord is / are suspected. As a result, in many prenatal ultrasound units, suspected sonographic findings suggestive of or consistent with true knot of the umbilical cord are often disregarded, not documented, and patients are not uniformly informed of this potentially life-threatening condition, which carries an associated considerable risk of stillbirth. This commentary will address current perspectives of prenatal sonographic diagnostic and management challenges associated with true knot(s) of the umbilical cord in singleton pregnancies.

Additional benefits of three-dimensional ultrasound for prenatal assessment of twins.

Three-dimensional ultrasound (3DUS) may provide additional information for prenatal assessment of twins. It may improve the diagnostic confidence of dating, nuchal translucency (NT) and chorionicity assignment in twin pregnancies. The "virtual 3DUS placentoscopy" can guide selective fetoscopic laser photocoagulation (SFLP) to treat twin-twin transfusion syndrome (TTTS). Volumetric assessment of the dysmorphic acardiac twin with the Virtual Organ Computer-aided Analysis (VOCAL) software is more accurate than the conventional ultrasound measurement. Twin anemia polycythemia (TAP) sequence and selective intrauterine growth restriction (sIUGR) may be clinically monitored with 3DUS placental volume (PV) and power Doppler vascular indices. Congenital anomalies are more common in twins. Evaluation of fetal anomalies with 3DUS could assist perinatal management. The 3DUS power Doppler can provide a better understanding of true and false umbilical cord knots, which are commonly found in monoamniotic (MA) twins. Single demise in monochorionic (MC) twin pregnancies can cause severe neurologic morbidity in the surviving co-twin. Prenatal prediction of brain injury in the surviving co-twin with unremarkable neurosonographic examination is difficult. The 3DUS power Doppler may aid in prenatal detection of subtle abnormal cerebral perfusion. Prenatal assessment of conjoined twins with 3DUS is important if emergency postnatal surgical separation is anticipated. There is no significant additional advantage in using real-time 3DUS to guide prenatal interventions. Assessment of the cervix and pelvic floor during twin pregnancies is enhanced with 3DUS. Due to lack of high-quality studies, routine prenatal 3DUS in twin pregnancies needs to be balanced with risks of excessive ultrasound exposure.

Intrauterine fetal death due to true knot on umbilical cord: Report of two cases

The incidence of a true knot of the umbilical cord is not only very low ranging from 0.3% to 2.1%, but also it often remains undiagnosed antenatally despite the availability of ultrasonography (USG). If the true knot remains tight, it may impede the circulation of the fetus and results in intrauterine fetal death (IUFD). We reported two cases of the true knot of the umbilical cord that ultimately led to fetal demise. Our first patient was a 25-year-old primigravida, with a singleton pregnancy of 35 weeks reported with complaints of absent fetal movements for the day. On examination, the patient was normotensive; the fundal height corresponded with the gestational age. The fetal heart sounds were absent on auscultation. The ultrasound confirmed IUFD. Labor was induced and the patient underwent uneventful vaginal delivery. However, the baby was stillborn. Two tight loops of the umbilical cord around the neck with true knots were found. Our second patient was gravida 2 with previous cesarean delivered 3 years back. She was pregnant 25 weeks and had a loss of fetal movement for the day. The fetal heart sounds were absent. She went into spontaneous labor and delivered vaginally. On examination, the true knot in the umbilical cord was seen.

脐带脱垂合并脐带真结1例报告并文献复习

脐带脱垂合并脐带真结1例报告并文献复习

460: The significance of true knot of the umbilical cord

460: The significance of true knot of the umbilical cord

731: True knot of the umbilical cord and long-term neurological morbidity of the offspring

731: True knot of the umbilical cord and long-term neurological morbidity of the offspring

42: Fetuses with fetal growth restriction (FGR) have elevated proteasome levels and activity

To increase lean body mass, the rate of fetal protein synthesis must exceed that of protein breakdown. The ubiquitin-proteasome system is an assembly of enzymatic activities with a key role in protein degradation and homeostasis. Environmental stressors switch the constitutive proteasome (cPROT) to immunoproteasome (iPROT), a quality control proteolytic machinery effective also in the absence of inflammation. Our hypothesis was that FGR fetuses have upregulated levels and enzymatic activity of the proteasome. We analyzed maternal blood, cord blood, and placenta of 70 singleton pregnancies of which 37 were complicated by FGR (EFW< 10%, Table). FGR occurred in the context of preeclampsia with severe features (sPE, n=23), identifiable causes (n=2: CMV infection, true cord knot) or idiopathic factors (n=12). Proteasome levels were measured using ELISA for cPROT and iPROT 20S subunit. Lytic activity was analyzed with fluorogenic substrates for caspase-like (CAS-L), chemotrypsin-like (CHE-L) and trypsin-like (TRY-L) activities. Specificity was confirmed with proteasome inhibitors MG132 and ONX. Placenta was stained for β5 (cPROT) and β5i (iPROT) subunits. Controls were idiopathic preterm births (iPTB) without fetal or placental inflammation. Data was adjusted for gestational age (GA) at birth. 1) The highest maternal cPROT levels were seen in sPE, independent of FGR (sPE p=.003, FGR p=.259, 2-way ANOVA, Fig A); 2) There was no correlation between cord blood and maternal proteasome levels (r=-.009, p=.96); 3) Fetuses with FGR had heightened CHE-L enzymatic activity independent of maternal proteasome levels or activity, sPE status or GA (adjusted p=.04, Fig B); 4) Cord blood proteasome activity of FGR fetuses was inhibited by MG132 and ONX with maximal effect on CHE-L activity which was reduced to 1.7% and 0.6%, respectively; 5) FGR placenta displayed intense β5i staining in trophoblasts and stromal cells suggestive of upregulated iPROT (Fig C). FGR fetuses display a significant upregulation in proteasome enzymatic activity independent of maternal compartment and etiology.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

EP02.11: True knot in the umbilical cord: how accurate can we be?

EP02.11: True knot in the umbilical cord: how accurate can we be?

Fetal gender and umbilical cord characteristics at birth

Objective To determine fetal gender on umbilical cord parameters. Methods Umbilical cords were prospectively collected from uncomplicated, singleton, term pregnancies, which ended either by elective cesarean section or spontaneous vaginal delivery. Data regarding obstetrical history and pregnancy outcome were collected. Various cord parameters were examined including, length, number of coils, umbilical cord index (UCI), which demonstrate the ratio between number of coils and cord length, site of placental insertion, direction of coiling and the presence of true knots. Results Overall, 154 umbilical cords were collected, of them 84 from male and 70 from female newborns. No differences were found regarding obstetrical history parameters or pregnancy outcome between the groups. The umbilical coiling index was significantly higher in female compared to male newborns (0.183 coils/cm versus 0.157 coils/cm, p=.006) due to higher number of cord coils (12.25 ± 5.31 vs. 10.17 ± 3.96, p=.007), with no difference in cord length (66.48 vs. 64.61 cm, p=.372). These differences remained statistically significant even after correction for gravidity, parity and gestational age using multiple linear regression analysis. Conclusion Female newborns having higher umbilical cord index, compared to male as a result of more coils, with no length dissimilarity.

Knot calculation for spline fitting based on the unimodality property

Determining the knot number and location is the most challenging problem in spline fitting. In this paper, we proposed a two-stage framework for calculating knots in spline fitting based on the unimodality property. Here, the unimodality property means that the jumps of the highest order derivative of the B-spline approximation at the initial knots closest to the true knots from the sampled B-spline are local maximal. Thus, in the first step, we search for the knots associated with local maximal jumps to locate in which intervals true knots should be. Here, the sliding window algorithm is adopted to search for the knots from an initial knot vector. Then, the knots selected in the first step are adjusted locally to reduce the knot number and improve fitting performance. Furthermore, we provide an error estimation for the B-spline approximation when data points are sampled uniformly and densely from a spline, and the initial knots are chosen as the parametrization for the data points. Such an estimation provides evidence of the unimodality of the least squares B-spline approximation. The proposed method is a significant improvement upon the method used in Kang et al. (2015) based on algorithm efficiency and fitting performance.

Experience of prenatal diagnosis of true knots of the umbilical cord during ultrasound examination in the third trimester of gestation

Despite the rapid technological advance, the expansion of prenatal ultrasound diagnosis, as well as the accumulation of experience by both domestic and foreign experts, prenatal recognition of true knots of the umbilical cord causes significant difficulties. Three cases of successful ultrasound diagnosis of true knots of the umbilical cord and brief review of the literature are presented.

Excessively long umbilical cord: a preventive factor of miserable outcomes of pregnancies with true umbilical cord knots

Objective: We examined the clinical significance of pregnancies with true umbilical cord knots related to umbilical cord length.Methods: The material reviewed consisted of the total population of Japanese women who gave birth to singleton babies at 34–41 weeks’ gestation at Japanese Red Cross Katsushika Maternity Hospital between 2002 and 2017.Results: During the study period, there were 32,315 Japanese women who gave birth to singleton babies at 34–41 weeks’ gestation. Of these, true umbilical cord knots were recognized in 209 cases (0.6%). In addition, excessively long umbilical cords were recognized in 98 of the 209 cases (46.9%). On multivariate analysis, true umbilical cord knots were associated with intrauterine fetal demise (adjusted OR 5.65, 95% confidence interval [CI] 1.9–17, p = .02) and excessively long umbilical cord (adjusted OR 8.26, 95% CI 6.0–11, p < .01). The incidence of intrauterine fetal demise in cases with the excessively long umbilical cord (0%) was significantly lower than that without excessively long umbilical cord (4.2%, p = .04), and it was not different measurably from that without true umbilical cord knots (0.3%, p = 1.00).Conclusions: Excessively long umbilical cords may contribute to the decreased risk of intrauterine fetal demise in singleton pregnancies delivered at ≥34 weeks’ gestation.

Complete hydatidiform mole with a twin pregnancy at 26 weeks: a rare obstetric complication.

Complete hydatidiform mole with a twin pregnancy at 26 weeks: a rare obstetric complication.

ЭТИКО-ФИЛОСОФСКИЕ АСПЕКТЫ ПРОБЛЕМЫ ЭВТАНАЗИИ

The focus of the author’s attention is the problem of active euthanasia and assisted suicide. Relying on the reasoning of modern philosophers and representatives of bioethics, the author shows that the true knot of the problems associated with these phenomena is concentrated around the specificity of the medical profession and respect for the autonomy of a patient’s personality. Separate consideration is also given to the topic of using painkillers. Highlighting various points of view, the author concludes that the position of supporters of euthanasia and assisted suicide is based on the absolutization of the value of a personality’s autonomy and leads to such morally questionable, non-medical reasons for death as “life fatigue”, “loss of the meaning of life”.

Prenatal detection and obstetric management of true umbilical cord knots using color Doppler and 4D ultrasonography: a report of two cases and literature review

Abstract Background True umbilical cord knots are common incidental findings at birth, however, there are limited reports of antenatal diagnosis. True knots are mostly asymptomatic; however, cord related accidents may be encountered. Case presentation We present two cases we diagnosed and followed-up antenatally. We reviewed previous literature and found 16 reports of antenatal diagnosis. In addition to foregoing established risk factors, we noticed an increased risk at first trimester screening in our cases. Conclusions Modern ultrasonography (USG) technology applications are valuable for monitoring knot architecture and compression. We propose monitoring the baby with daily kick counts and biweekly cardiotocography after 28–30 weeks of gestation. Weekly umbilical Doppler pulsatility (PI) measurements of afferent and efferent loops with respect to the gestational age, aids in monitoring the tightness of the knot. The timing and route of delivery should be necessitated by obstetric indications. Vaginal delivery is possible under continuous fetal monitorization during labor.

True knot at the time of delivery: electronic fetal monitoring characteristics and neonatal outcomes.

Objective:Determine the association between electronic fetal monitoring and neonatal outcomes in the setting of a true knot at delivery.Study Design:This was a planned secondary analysis of a prospective cohort of 8,580 women. Patients with and without a true knot were compared and the primary outcome was repetitive late decelerations occurring with at least 50% of contractions. Confounders were adjusted for using logistic regression.Results:8,580 patients met inclusion criteria and 49 (0.57%) had a TK. There was no significant difference in the rate of repetitive late decelerations in patients with TK (aOR 1.04; 95% confidence interval [CI] 0.25–4.40),other electronic fetal monitoring parameters, or neonatal outcomes.Conclusion:Neonates with true knots who are delivered at term have similar electronic fetal monitoring characteristics compared to those without true knots and no detectable difference in neonatal morbidity; thus, calling into question the clinical significance of a true knot at term.