For centuries there has been fascination with umbilical cord. The cord itself, as well as the remnant of the umbilical cord, a navel (umbilicus) on the adult abdomen, had ascribed mystical powers in ancient and some present cultures. It represents the “life source”, or the “entry” and “exit” point of human will and source of energy that makes connection to the surrounding world. Regardless of umbilical cord mystical powers, it was always obvious that it provides the life support to the fetus, and therefore, represents the major feto-maternal unit. All building blocks required by the developing fetus are exchanged with waste materials through this blood flow highway. As such, any morphologic umbilical cord abnormalities will affect blood flow and modulate function of the end units that the same connects-placenta and fetus [1].

The umbilical cord length at term has wide variation with extremes ranging from no cord to lengths up to 300 cm. At birth, the mature normal umbilical cord is between 50 and 60 cm in length and 37.7 ± 7.73 mm in diameter [2].

The umbilical cord can be long or short and there may be as many as 40 spiral twists in the cord as well as false and true knots. Short cords, defined as cords <35 cm long, are seen in 0.4–0.9% of pregnancies and some studies revealed an incidence of up to 3–10% of all umbilical cords. Long cords, defined as cord length longer than 80 cm according to some studies or 100 cm according to others, are seen in 3.7–4% and 0.5% of all umbilical cords during pregnancies respectively [3].

Umbilical cord length is one of the factors documented as a definite risk for poor fetal outcome. There is an association of abnormal cord length with neurological abnormalities and low IQ values. Excessively long or short cord may be the cause of hematoma and thrombosis of cord vessels and the placental surface, thus causing fetal death and or thrombocytopenia [4].

Causes of differences in cord length are unknown; however, the length of the umbilical cord is thought to reflect the sufficient space in the amniotic cavity for movement and the tensile strength applied to the umbilical cord during fetal movement 5.

Short cords can interfere with the mechanics of labor and delivery while exhibiting changes in fetal heart rate patterns. This restriction of decent (which is relative to the placental position and insertion) leads to an increase in the incidence of caesarean section, forceps and vacuum extractions. Other complications of excessively short cords include delay in second stage of labor, retained placenta, placental abruption, rupture of umbilical cord, inversion of uterus, birth asphyxia, and cord herniation [6].

On the other hand, long umbilical cord is directly associated with poor fetal outcome and umbilical cord accidents especially fetal entanglement and true knots. Placental changes associated with long cords are suggesting blood flow disruption or increased resistance. Other complications of excessively long umbilical cords include cord prolapse, torsion, and delivery complications [7]. In our locality, there is scarcity of data on umbilical cord length and cord abnormalities with relation to fetomaternal outcome [8].  Several known studies have attempted to identify the length of the umbilical cord in the intrauterine period to evaluate whether maternal and fetal complications can be predicted [9].

It is possible to measure umbilical cord length in the first and second trimester ultrasonographical, but it is not possible to directly measure the umbilical cord length in the third trimester. Therefore, a new ultrasonographic method for prediction umbilical cord length is being tested in this study.

 In this study, umbilical cord length index has been tested as a new ultrasonographic method for detection of umbilical cord length and the correlation between umbilical cord lengths with perinatal complications among the studied cases has been highlighted.

The current study was a prospective cohort study conducted at the Women Health University Hospital, Assiut. The study was approved by Assiut medical school ethical review board (ERB) and was designed and reported according to the revised recommendation of Clinical Trials. Gov for improving the quality of reporting RCTs (NCT03604887). All participants gave their informed consent to participate in the study.

Pregnant women who were ≥37 weeks with a singleton pregnancy who attended labor unit during the study period either for vaginal delivery or CS were enrolled in the study if they met our inclusion criteria. We included women aged 18-35 years, with a singleton pregnancy, gestational age ≥37 weeks and accepted to participate in the study. Participants were excluded if they had preterm delivery, amniotic fluid abnormalities (oligohydramnios, polyhydramnios and anhydramnios), fetal growth restriction (FGR), premature rupture of membrane, multiple pregnancy, major congenital anomalies and maternal hypertension or diabetes.

Recruitment

One of the study researchers approached all included women and collected the baseline data. A detailed history was taken including patient’s age, parity, history and number of abortions if present, history of ectopic pregnancy, history of cord prolapse or stillbirth and history of CS. The presence of any medical risk was also reported. Gestational age was determined according to the last menstrual period. In those who did not know the time of their last menstrual period, ultrasound fetal biometry was considered in determining the gestational week.

Intervention

All patients were clinically examined with recording of maternal pulse and blood pressure was done. Abdominal examination including fetal heart sounds, fundal level and fundal grip also was done.

All ultrasound evaluations were performed using the (Mindray DP 10, china) Instrument using a 3.5-MHz convex transducer probe. Measurements were made in the absence of fetal movement and fetal breathing. Fetal biometry was calculated using BPD, FL and AC. Amniotic fluid index was calculated using sagittal view of the 4 amniotic fluid quadrants. Placental site and fetal presentation were noted.

Regarding umbilical cord length index, it was calculated by counting umbilical cord rings in each amniotic fluid quadrant. When the anatomical structure of the umbilical cord is considered, it is folded in amniotic fluid; therefore, it is not possible to measure its complete length by ultrasound. The folds appear as umbilical cord rings, side-by-side at the sagittal sections. The idea that counting the number of umbilical cord rings can be used to predict the length of the umbilical cord is the hypothesis of this study. Umbilical cord ring was considered accurate when it showed the typical view of one central large vein with two surrounding smaller arteries.

We did scoring of umbilical cord length index as follow: 1 point was given for each quadrant that contained umbilical cord ring and 0.5 point was given for each umbilical cord ring in one quadrant. Every quadrant was evaluated in this manner, and the total score was calculated.

If vaginal delivery was decided, careful intrapartum fetal monitoring was done using CTG. Any signs of fetal distress were noted allowing early intervention. Intrapartum complications including cord prolapse, placental separation and meconium-stained amniotic fluid (MSAF) were recorded. Mode of delivery vaginal or cesarean will be noted.

After delivery of the fetus, umbilical cord was clamped at two places at least one inch from the fetal abdominal wall and cut in between. From the cut end up to fetal umbilicus and placental attachment, umbilical cord length was measured with flexible tape in cm and added to the length of the part left in the neonate.

Follow Up

We recorded the following parameters after delivery of the fetus: sex of the newborn, newborn was weighed after cutting the cord within half an hour of delivery and Fetal outcome was studied by Apgar score at 1 and 5 minutes. Examination of umbilical cord was done for the following: The presence of any loop around neck, trunk or shoulder. Number of loops of cord and positions, presence of True knots and cut section of the cord examined for the number of arteries and veins.

Study Outcomes

The primary outcome was to detect the sensitivity, specificity and accuracy of "Umbilical cord length index" in diagnosis of long and short umbilical cords. Secondary outcomes included Correlate the umbilical cord abnormalities with the cord length, Correlate the adverse neonatal outcomes with the cord length and the rate of emergency CS or operative delivery in those with abnormal cord length.

Statistical Analysis

All data was analyzed using SPSS software Chicago, IL, USA, version 21. Receiver operating curve (ROC) analysis was used to investigate reference index values for short and long umbilical cords. Sensitivity and specificity values of the determined cut-off points were given within the scope of the study. The area under the ROC curve for the determined point was then obtained with a 95% confidence interval. Finally, sensitivity, specificity, general accuracy, and plus and minus interpretation power values for index values of normal umbilical cord length were obtained using the cut-off values of short and long umbilical cord indexes. The Shapiro Wilk test was used to test the normality assumption of the data, and the variance homogeneity assumption was tested using the Levene test. Values were expressed as median (25th percentile–75th percentile) or n (%). Comparisons were made using a Chi-Square or Kruskal-Wallis test. P value <0.05 was considered as a significant value.

This study comprised 300 women attending delivery unit of the Woman's Health University Hospital. Assiut University, Egypt for normal labor or planned elective CS.

As shown in table 1, the sociodemographic and ultrasonographic data of the studied group shows that majority of cases were between 25 and 29 years old (42.3%). Most of the studied cases were in the first or second pregnancy (146, 48.7%). Gestational age was between 37 to 42 weeks with a mean of 38.05 ±.989. 32 cases (10.6%) were associated with medical risk. 15 of them (4.9%) had different risks. Mean fetal biometry was 38 ± 0.9 weeks and mean AFI was 13± 4.4 cm.

(Table 2) shows the mean values of the umbilical cord length index. Short umbilical cord cases were 10 (3.3%). Their mean UC length index was 1.9 ± 0.51. Normal umbilical cord cases were 269. Their mean UC length index was 3.27 ± 1.07. Long umbilical cord cases were 21 (7%). Their mean UC length index was 5.09 ± 0.86.

- UC length index can be used to discriminate between short and normal UC length at a cutoff level of < 3.25, with 100% sensitivity, 53.9% specificity, 68.4% PPV and 100% NPV (AUC = 0.85 & p-value < 0.001).

UC length index can be used to discriminate between long and normal UC length at a cutoff level of > 4.75, with 57.1% sensitivity, 91.5% specificity, 87% PPV and 68.1% NPV (AUC = 0.91 & p-value < 0.001).

(Table 3) shows newborn characteristics in relation to umbilical cord length. 30% of newborn cases who are < 2.5 kg was associated with short umbilical cord. Most malpresentation cases, 4 out of 7 cases, were associated with short umbilical cord. The rest were associated with normal cord and no cases were associated with long cord. (Table 4) shows the relationship between umbilical cord length, perinatal and newborn complications. Most complication noted was neck loop. Non reassuring CTG also was higher among cases with long and short umbilical cord (3,14.2% & 3,30%) respectively. Cord loop around fetal neck and true knots were significantly higher among newborns with long UC (11, 52.3% & 6, 20.6%) respectively. Furthermore, cord prolapse occurred in a single case with long cord (1,4.7%) and in another case with normal cord. Meconium-stained amniotic fluid was associated with all varieties of cord lengths whereas placental separation was significantly higher among cases with short UC (2,20%). There was significant relation between cord length and need for newborn resuscitation. Long and short cord cases were associated with more rate of newborn resuscitation.

(Table 5) the effect of neck loop on perinatal outcome. One cord loop around fetal neck was not associated with severe complications. On the other hand, 2 and 3 cord loops had higher incidence of adverse outcomes. (Table 6) demonstrates that Umbilical cord true knots were associated with significant effect on intrapartum fetal condition, 1st and 5th minute Apgar score. There was no significant effect on mode of delivery.

Table 1: Sociodemographic , clinical and ultrasonographic data in study group.

Table 2: Mean values and diagnostic performance of the umbilical cord length index parameters.

PPV: Positive Predictive Value.     AUC: Area under Curve

NPV: Negative Predictive Value.

Table 3: The newborn characteristics in relation to cord length.

Table 4: The relationship between umbilical cord length, perinatal and newborn complications.

* Statistically significant difference < 0.05

Table 5: Effect of neck loop on perinatal outcome.

Statistically significant difference < 0.05

Table 6: Effect of true knots on perinatal outcome.

* Statistically significant difference < 0.05

Several known studies have attempted to identify the length of the UC in the intrauterine period to evaluate whether maternal and fetal complications can be predicted [9]. In this study, UC length index has been tested as a new ultrasonographic method for detection of UC length and the correlation between the UC length and perinatal complications among the studied cases has been highlighted.

In recent years, several studies have been conducted in which UC length was measured in the first and second trimesters. However, these have not yet been adapted to routine obstetric practice. Moreover, it was not possible to directly measure the UC length in the third trimester [9]. Durand et al. tried to evaluate the UC length by using two ultrasound devices simultaneously. Blood flow velocities and blood flow velocity fluctuations were recorded by Doppler ultrasonography, and the time interval in both systolic flow velocities was calculated and recorded. The calculated cord length did predict the actual cord length with a high index of sensitivity but the necessity for the simultaneous use of two ultrasound devices was the greatest limitation in this study. In other words, ultrasound must be carried out by two obstetricians. Therefore, although the method was successful, it was difficult to implement [10].

Qin et al. used the UC coiling index as a method for predicting postnatal UC length. In their study, longitudinal views of the UC were obtained at maximum magnification, and the distance between coils was measured from the inner edge of an arterial wall to the outer edge of the next. The UCI was defined as the reciprocal of the average distance between a pair of coils. They correlated the results with postnatal UC length. They concluded that whilst UCI could be measured easily and reliably in the second trimester, these estimates did not accurately reflect the UCI at term [11].

Katsura et al. reported prenatal measurement of the UC length using MRI. They compared the UC length measured prenatally using the three-dimensional image of the UC constructed by AZE virtual place system on MRI (M-length) with the actual length postnatally (R-length). While using MRI to measure UC length proved to be a reliable and effective method, the technical difficulty in daily use of MRI and the relatively unsuitable cost hindered its use as a routine method for predicting UC length [12].

A novel technique for prediction of the UC length was introduced by Sahin et al. called UC length index. This method also helped in detection of complications due to short and long UCs in both the intrapartum and postpartum periods. They concluded that calculation of the UC length index could be easily used to predict short and long UCs during routine amniotic fluid evaluation in full-term pregnancies [8].

In the present study the mean UC length was 59.96 cm and ranged from 30 to 105 cm. This is comparable with the findings of Ahmed & Nuggedalla where the mean UC length was 60.5 cm and Agwu et al. where the mean UC length was 57 cm and ranged from 22 to 124 cm [13, 14]. However, this was higher than 52.7 cm reported by [15].

The reason for the difference in the mean values of the UC length obtained in these studies is not very clear but may be because the UC length is influenced by environmental and genetic factors [15]. Although it is not fully understood what controls cord length, various authors correlate the UC length with fetal activity and movement [16]. It is suggested that sufficient space in the amniotic cavity for movement and the tensile force applied to the UC during fetal movements are the two main factors that determine the cord length. However, other studies using animal models have argued against the “stretch hypothesis,” stating that the UC continues to grow throughout pregnancy in an almost linear fashion [15].

The incidence of short cords in the present study was 3.3 % of all deliveries. This matches with Balkawade’s and Shinde’s study in which short cord cases were 5.9% of all cases [2]. Moreover, it is similar to other reported incidence of short cords which ranged from 2% to 10% in other studies [14]. However, this is different from the incidence of 8.2% of short cords in the study 7.2% [9], [15]. This may be attributable to the lower cut off point for short UC (< 35 cm) used in the current study compared to 40 cm in Adesina ar al.’s study [15]. The incidence of 3.3% in this study is however higher than 0.7% reported by Agwu et al. The marked difference in the reported low prevalence of short cord in that study may have been influenced by the much lower cut off of (<32 cm) used in the definition of short UC in their study.

In this present study, the incidence of long UC was 7% which is similar to 7% by Agwu et al. and 9.3% by Adesina et al. It is, however, higher than 3.2% reported by Sahin et al. The significance of long UCs resides in the fact that they may be directly associated with poor fetal outcome and UC accidents such as fetal entanglement, knot formation and torsion [17].

The calculated UC length index in this study ranged from 1 to 7.5 with mean of 3.35±1.17. The calculated cut off value for short cord was <3.25, with 100% sensitivity, 53.9% specificity, 68.4% PPV and 100% NPV (AUC = 0.85 & p< 0.001). This means that UC length index can detect short cord very accurately but it can’t rule it out very precisely. The cut off value for short UC. was 3.75 with a sensitivity of 92% and specificity of 80%. The specificity of the UC length index in the detection of short cord in our study appeared to be lower than that in Sahin et al.’s study. This is likely attributed to the lower cut off value of short cord in this study compared [9].

Regarding long UC, the cut off value of UC length index was >4.75, with 57.1% sensitivity, 91.5% specificity, 87% PPV and 68.1% NPV. On the other hand, Sahin et al, calculated the cut-off value as >6.25 for a long UC with a sensitivity and specificity of 85% and 64% respectively. The difference in the sensitivity between the two studies may also be attributed to the higher cut off value for long cord in Sahin et al’s study compared to the present study [9].

UC length was positively correlated with birth weight (P< 0.001). Fetuses with shorter UC were likely to have lower birth weight. In 30% of cases with short UC, Fetal birth weight was <2.5 kg. This could be explained by the fact that as the fetus grows the UC also increases in length. This is matched with Agboola who reported a significant positive correlation between the UC length and fetal weight [18]. Similarly, Wu et al. found a statistically significant relationship between the UC length and birth weight [19].

Regarding fetal presentation, fetuses with malpresentation were associated more with short cords. A total of 3 cases (30%) with short cord were breech and 1 case (10%) was transverse lie, while 3 cases (0.8%) only of normal cord fetuses had malpresentation. Njoku et al. also reported similar results. They showed that the mean UC length was 61.23 ± 14.95 with cephalic presentation which was longer than 54.29±13.25 with breech presentation. This may be explained by the inability if the fetus to move freely in case of short cord making it difficult to rotate to cephalic presentation near term [20].

UC length was found to have a significant effect on the perinatal complications among the studied cases. Of the total, neck loops were seen in 57 cases. In cases with a long cord the incidence of neck loops was 52.3 % versus 10% and 16.7 % in cases with a short cords and normal cords respectively. This was statistically signi?cant (P<0.001). This is comparable to Balkawade & Shinde’s results with a total of 20.7 % (207 cases) of neck loops, from which 67.9 % of cases had long cords, 1.7% and 19.1 % of cases had short cords and normal cords respectively [2].

Moreover, Neck loops were found to have significant effect on perinatal outcome. Number of neck loops also contributed to the effect. One cord loop around fetal neck was not associated with significant adverse outcomes. In contrast, 33.3% and 100% of 2 and 3 neck loop cases were found to have non reassuring CTG. Additionally, 66% and 100% of 2 and 3 neck loop cases were found to have 1st minute Apgar score that was <7. This means that fetuses with more than one neck loop were more liable to intrapartum fetal distress and fetal hypoxia.

Shrestha & Singh also studied nuchal cord and Neonatal outcome. He recorded Apgar score at 1 and 5 min and the need for neonatal unit admission. 1st minute Apgar score < 7 was present in 24.78 % (n =29) of newborns in study group and 14.68 % (n =58) of newborns in control group, which was statistically signi?cant (p= 0.01) [21]. Regarding mode of delivery, no difference was noted between cases with and cases without neck loops.

In this study true knots also were higher among long cords. There was 20.6% of cases with long UC associated with true knots in contrast to 8.9% of cases with normal cord. Cases with short cords had no true knots in the present study. The difference was statistically signi?cant (P<0.001). Balkawade & Shinde also said that true knots were associated with a higher mean cord length of 77.56 cm for cases with true knots than those cords without true knots [2]. The presence of cord true knot was also found to have adverse effect on perinatal outcome. In 20.6 % of cases with true knots, non-reassuring CTG was noted. Additionally, 24.1 % of cases had <7 1st minute Apgar score.

In the present study cord prolapse also proved to be highly associated with long cord. In 4.7% of cases, long cord was associated with cord prolapse in contrast to 0.4% and 0% of cases with normal and short cords respectively. This was statistically significant with p< 0.001.

There were 19% and 20% of cases with long and short cord respectively had meconium-stained amniotic fluid, while 8.1% only of cases with normal cord had the same finding. Atalla et al., on the other hand, found no statistically signi?cant differences between the mean UC morphologic length in groups with or without meconium staining of amniotic fluid [22].

Cases complicated by placental separation showed significant negative correlation with UC length. In the present study, 20% of short cord cases were complicated by placental separation, in contrast to 0.4 % in normal cord cases versus none in long cord cases. This is consistent with Njoku et al. Who found that placenta separation was significantly higher among fetuses with short UC than normal UC [20]. Moreover, Non reassuring CTG and intrapartum fetal distress were also noted mostly among cases with short cord with percentage of 30% compared to 14.2% of long cord and 1.4% of normal cord cases.

Krakowiak et al in their study reported an increase in hypoxic–ischemic encephalopathy, fetal distress, and infant death and low birth weight and a twofold increase in risk of death among term infants born with short cords [23].. Did not find an increase in intrapartum fetal distress and birth asphyxia with change in length of UC [20]. This is like the study by Wu et al. who reported no association between UC length and antepartum and intrapartum fetal wellbeing [19]. On the contrary, Agwu et al. found an increase in intrapartum fetal distress and birth asphyxia among long cord group [13]. These differences between studies may be related to the difference in patients’ selection for the study, intrapartum monitoring, presence of neck loops with long cords and caesarean sections rates in different studies.

The rate of newborn resuscitation among cases with abnormal cord length either long or short was significantly higher. Out of the studied cases, 38% of long cord cases and 40 % of short cord cases needed resuscitation in contrast to 16.7% of normal cases. Also 1st and 5th minute Apgar score were lower (<7) among short (30%) and long (23.9%) cord cases respectively, while 8.9 % only of normal cord cases had the same result. There was 9.5% and 10% of long and short cord cases with 5th minute Apgar score < 7 compared to 2.2% only of normal cord cases. Algreisi et al. found that Apgar score <7 at one minute was statistically significant in long and short cord group more the Normal cord group. Their results proposed an association of acidemia and birth asphyxia (Apgar <7 at one minute) with short cords. Spellacy et al. showed that all cord complications resulted in signi?cantly low 1st minute Apgar scores [24].

The rate of NICU admission was higher among cases with abnormal cord length. There were 3 cases (14.2%) with long cord and 2 cases (20%) with short cord admitted to NICU. Algreisi et al. also reported that short UC was associated with higher rates of NICU admissions. This is probably related to the high rate of lower Apgar score among cases with short cord and the associated fetal asphyxia and fetal distress [25].

However, our study is not without limitations. We included deliveries from tertiary hospital in a limited period which may have affected the results. It may be necessary to conduct a larger sample size to be able to test the feasibility of UC length index better and to address the relationship between cord length and fetal outcome well. Also, our study didn’t utilize the intrapartum evaluation with Doppler ultrasound to possibly determine cord length and abnormalities as to reduce feto-maternal complications during delivery.

The calculation of UC length index can be used to predict complications due to short and long UCs, in both the intrapartum and postpartum periods. It is very applicable and does not need an experienced obstetrician to measure it. The evaluation is noninvasive and can be performed by a single physician during routine amniotic fluid measurement.

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