Adverse pregnancy outcomes and the abnormal umbilical cord coiling index

Abstract

BACKGROUNDS:

The abnormal umbilical cord coiling index (UCI) may be one of the ways to predict adverse pregnancy outcomes. This study attempted to determine the association between abnormal UCI and maternal, fetal, and neonatal outcomes.

METHODS:

This longitudinal study was conducted on 400 women referred for delivery from April to August 2021. UCI was calculated by dividing the total number of coils by the total length of the umbilical cord in centimeters. In eligible cases, the length of the umbilical cord and the number of vascular coils along the total umbilical cord were measured after birth. UCI less than the 10th percentile and more than the 90th percentile was considered abnormal, and between the 10th and 90th percentiles was considered normal. Data were analyzed using SPSS version 20. P < 0.05 were considered statistically significant.

RESULTS:

The mean length of the umbilical cord was 56.12±8.38 cm, the number of umbilical cord rings was 13.70±3.51, and the UCI was 0.24±0.07. In the regression analysis, women with gestational diabetes had a significant association with abnormal UCI (P = 0.044). Thus, the probability of abnormal UCI was about 3.5 times higher in women with gestational diabetes than in normal pregnancies. Also, the history of stillbirth had a significant association with abnormal UCI (P < 0.05).

CONCLUSION:

It is recommended to perform a UCI examination after delivery as part of a neonatal examination to find an explanation for maternal, fetal, and neonatal outcomes.

Keywords

Abnormal coiling pregnancy outcomes umbilical cord

1 Introduction

The life, well-being, and growth of the fetus are supported by the umbilical cord, which is the main maternal and fetal unit and allows the exchange of gas and nutrients. The main structure of a normal human umbilical cord consists of a spiral of 3 blood vessels (2 arteries and 1 vein) protected by Wharton’s jelly, amniotic fluid, coiling patterns, and vascular torsions of the umbilical cord [1]. One of the most mysterious and attractive features of the human umbilical cord is the coiling or spiraling of its blood vessels [2]. In recent years, there has been increasing interest in the study of umbilical cord coiling and its role. The length of the umbilical cord in a term fetus is approximately 50 to 60 cm. On average, each umbilical cord has 11 coils, or spirals, along its length between the fetus and placenta [2, 3]. The coiling of the umbilical cord vessels occurs in the first 28 days of gestation; in addition, in approximately 95% of fetuses, the umbilical cord is coiled by the ninth week of gestation [1]. The number of coils in the first trimester is almost equal to that of the umbilical cord of term infants [2]. The umbilical cord coiling index (UCI) is defined as the total number of coils divided by the total length of the umbilical cord in centimeters. Rana et al. classified the frequency distribution of UCI as follows: less than the 10th percentile was referred to as hypo coiling, between the 10th and 90th percentiles as normal coil, and above the 90th percentile as hyper coiling [4, 5]. The mean UCI is approximately 0.2±0.1 of the complete circle in centimeters. This means that there is 1 coil for every 5 cm of cord length [3]. With the availability of ultrasound techniques, it is possible to examine the umbilical cord for abnormalities before birth [3]. Assuming that umbilical cord coiling is fully developed by the end of the first trimester, actual UCI can be predicted by ultrasound assessment in the second trimester [6]. Several studies have suggested that abnormal UCI (hypo coiling or hyper coiling) is related to adverse perinatal outcomes [3, 7]. However, there is disagreement between different studies. In a recent study has recognized that neonates of mothers with gestational diabetes are more likely to have hypercoiled umbilical blood vessels [8]. But, the other study showed no significant association between GDM and occurrence of abnormal umbilical cord coiling [9].

Hypo-coiled umbilical cords have been associated with intrauterine fetal death, intrauterine fetal growth restriction, low Apgar scores, fetal congenital anomalies, abnormal positioning of the umbilical cord, fetal distress, and the presence of an umbilical artery [10]. However, not all studies are in agreement. In some studies, hypo- and hyper-coiled umbilical cords have not been associated with adverse outcomes; in addition, studies conducted on the relationship between abnormal umbilical cord coiling and adverse outcomes have small sample sizes. It is still not possible to consider an abnormal UCI as an independent risk factor for adverse pregnancy outcomes [10 –12]. Therefore, the aim of this study was to determine the association between abnormal UCI at the time of delivery and adverse pregnancy outcomes. If the current study establishes the association between the risk of adverse pregnancy outcomes and abnormal umbilical cord coiling, it is recommended to perform a UCI examination after delivery as part of a neonatal examination to find an explanation for perinatal morbidity and mortality."

2 Materials and methods

2.1 Study design and setting

A total of 400 pregnant women were included in this prospective and longitudinal study from April 1 to August 1, 2021. They referred to Rouhani Hospital for delivery (an educational hospital affiliated with Babol University of Medical Sciences, Babol, Iran).

2.2 Participants

Inclusion criteria were pregnant women with a gestational age of at least 28 weeks based on the first day of the last menstrual period or first-trimester ultrasound confirmation and a singleton pregnancy with cephalic presentation. Exclusion criteria were smokers, drug users, and women with multiple pregnancies, abnormal presentation, placenta previa, placental abruption, stillbirth, and more than 2 previous abortions. Data were collected after obtaining the ethical code (IR.MUBABOL.REC.1399.210). Written informed consent was obtained from all participants.

2.3 Sampling methods

The sample size was determined according to the objectives of the study. The final sample size was 396 subjects, based on the study by Najafi et al. (2018) [1]; in this regard, the mean UCI (comparison of the mean and the difference of the SDs in the groups) with a confidence level of 95% and a study power of 95% was considered using G*Power version 3. Some maternal characteristics (such as maternal age and other demographic characteristics of the mother), fertility records, and pregnancy complications (such as gestational hypertension and gestational diabetes) were recorded when the mother was admitted to the maternity ward of Rouhani Hospital.

2.4 Data collection tools

Variables related to the condition of the fetus and baby, such as fetal distress, the Apgar score, birth weight, admission to the neonatal intensive care unit (NICU), gestational age at the maternity hospital, and the time of the birth, were added. After birth, the umbilical cord was examined for an appearance by a member of the research team (medical student).

After the baby is born, the umbilical was fastened at the fetal conclusion and cut with scissors right after delivery. The placenta was allowed to isolated on its possess. The chord was disjoined 5 cm from the point of fetal implantation at the fetal conclusion. The complete umbilical cord, counting the placental conclusion and the baby’s umbilical stump, was measured at 5 cm. The entire length of the cord was measured by including the length of the placental conclusion of the cord additionally the length of the umbilical stump on the neonate. The number of total coils or spirals was checked from the neonatal conclusion to the placental conclusion of the line. The UCI was calculated by partitioning the number of vascular coils in a line isolated by the length of the line in centimeters. A vascular coil was considered a full circle (360^circ) of the umbilical cord vessels. Then, UCI was calculated by dividing the total number of coils by the total length of the umbilical cord in centimeters. The formula used to determine the UCI is a division by the distance of each coil in centimeters. UCI less than the 10th percentile was referred to as hypo coiling, between the 10th and 90th percentiles as normal coil, and above the 90th percentile as hyper coiling [4, 5]. Women with hypo- or hyper-coiled umbilical cords were compared with those with normal-coiled umbilical cords.

The data collection consisted of 3 parts: The first part included demographic, social, and fertility information completed in the labor department. The patients’ blood pressure was measured and recorded when they visited the hospital. The second part included information on pregnancy outcomes, such as preterm delivery and preeclampsia, gestational hypertension, gestational diabetes, abnormal fetal heart rate, and low birth weight (LBW) of the baby according to gestational age. The third part included information on the baby’s birth weight and gestational age at delivery and a history of hospitalization in the NICU obtained during labor and delivery until the patient was discharged. The information obtained was recorded and stored in the checklist. The body mass index (BMI) of the women was calculated using the formula: Weight in kilograms divided by the square of height in meters. Preeclampsia was considered systolic blood pressure ≥140 or diastolic blood pressure ≥90 with proteinuria (at least 300 mg in 24-hour urine).

2.5 Data analysis

The mean (±SD) and 95% CI for mean was used to describe the normal quantitative variables and the frequency (percent) was used for qualitative variables. The normality assumption of the variables in the study was assessed by the Kolmogorov-Smirnov test. Binary logistic regression analysis was used to examine the variables predicting abnormal umbilical coil (independent variables) individually (crude effects) and with the presence of variables in the study (adjusted effects), contains maternal, neonatal, and fetal outcomes (dependent variable), as well as to show their relationship. Since demographic characteristics and other factors may influence this relationship, these variables were included in the final analysis for adjustment. Odds ratio (OR) and 95% CI were used to show the effect size in the model. All analyses were performed using SPSS version 20 (SPSS Inc., Chicago, IL., USA). P values less than 0.05 were considered statistically significant.

3 Results

The present study was designed to determine the association between UCI and perinatal outcomes. This longitudinal and prospective study was conducted on 400 pregnant women. The demographic and fertility characteristics of women are shown in Table 1.

Table 1
Demographic and fertility characteristics of the studied women (n = 400)

Variable mean±SD

Age (years) 29.48±6.8

Weight before pregnancy or first trimester (kg) 66.42±11.9

Weight at the end of pregnancy(kg) 75.99±13.16

Weight gain during pregnancy (kg) 9.53±2.9

BMI (kg.m²) 25.27±3.6

Gestational age (weeks) 37.43±2.2

Gravida 2.12±1.2

Birth weight (gr) 3120.95±685.4

Variable No. (%)

Delivery NVD 175(43.8)

S.C 225(56.2)

Parity Nulliparity 150(37.5)

Multiparity 250(62.5)

Education Elementary 46(11.5)

High school 236(59)

University 118(29.5)

Job Housewife 356(89)

Employed 44(11)

Location City 197(49.3)

Village 203(50.7)

Variable	mean±SD
Weight before pregnancy or first trimester (kg)	66.42±11.9
Weight at the end of pregnancy(kg)	75.99±13.16
Weight gain during pregnancy (kg)	9.53±2.9
BMI (kg.m²)	25.27±3.6
Gestational age (weeks)	37.43±2.2
Gravida	2.12±1.2
Birth weight (gr)	3120.95±685.4
Variable	No. (%)
Delivery	NVD	175(43.8)
	S.C	225(56.2)
Parity	Nulliparity	150(37.5)
	Multiparity	250(62.5)
Education	Elementary	46(11.5)
	High school	236(59)
	University	118(29.5)
Job	Housewife	356(89)
	Employed	44(11)
Location	City	197(49.3)
	Village	203(50.7)

NVD, normal vaginal delivery; S.C, caesarean section; SD, Standard deviation; BMI, Body mass index.

According to the previous pregnancy records, 93 women (23.3%) had a history of 1 or 2 miscarriages, 4 women (1%) had babies with abnormalities at birth, 10 women (2.5%) had a history of preterm labor, 20 women (5%) had pre-pregnancy hypertension, 12 women (3%) had a history of macrocosmic births, and 85 women (21.3%) had a history of a medical disease. Complications and adverse pregnancy outcomes are shown in Table 2.

Table 2

Complications and adverse outcomes of pregnancy in the studied women (n = 400)

Pregnancy outcomes		N (%)
Preterm labor	yes	64(16)
	no	236(84)
Overt diabetes	yes	11(2.8)
	no	389(97.2)
Gestational diabetes	yes	71(17.8)
	no	329(82.2)
Preeclampsia	yes	29(7.2)
	no	371(92.8)
Pregnancy hypertension	yes	8(2)
	no	392(98)
Fetal distress	yes	37(9.3)
	no	363(90.7)
Low birth weight	yes	60(15)
	no	340(85)
Apgar less than 7 in the first minute	yes	18(4.5)
	no	382(95.5)
Apgar less than 7 in the fifth minute	yes	8(2)
	no	392(98)
admitted to NICU	yes	64(16)
	no	336(84)

APGAR, appearance, pulse, grimace, activity, and respiration; NICU = neonatal intensive care unit.

In examining the characteristics of the umbilical cord after delivery, the average length of the umbilical cord, the number of coiling in the length of the umbilical cord, and the average coiling index of the umbilical cord were shown in Table 3. Forty cases (10%) had a UCI less than the 10th percentile (i.e., hypo coiling), 320 cases (80%) had a UCI between the 10th and 90th percentiles (i.e., normal coil), and 40 cases (10%) had a UCI above the 90th percentile (i.e., hyper coiling). In total, 80 cases (20%) had abnormal UCIs, and 320 cases (80%) had normal UCIs.

Table 3

Characteristics of the umbilical cord after childbirth in the studied women (n = 400)

Characteristics	mean±SD	95% confidence interval for the mean	Minimum	maximum
Length (cm)	56.12±8.38	55.30–56.95	35	82
Number of coiling	13.70±3.51	13.35–14.04	6	24
UCI	0.2491±0.0741	0.2418–0.2564	0.09	0.47

UCI, umbilical cord coiling index.

The results of the regression model on the association between the index of abnormal coiling of the umbilical cord with demographic and fertility characteristics showed that women who had a history of stillbirth have a 6 times higher chance of abnormal coiling of the umbilical cord than other subjects (P = 0.048). In determining the association between maternal age and abnormal umbilical cord coiling, although this association was not statistically significant, on average, with an increase in the maternal age by 1 year, the chance of abnormal umbilical cord coiling increased by 1% (P = 0.455). It was also observed that for every 1 kg/m² increase in BMI, the possibility of abnormal umbilical cord coiling increased by 2%, which was not significant (P = 0.609). No significant association was found between other demographic characteristics and abnormal UCI (Table 4).

Table 4

The association between abnormal umbilical cord coiling index and demographic characteristics and adverse pregnancy outcomes in univariate and multivariate regression analysis (n = 400)

Variable	subgroup	univariate analysis (crude effects)			Multivariate analysis (adjusted effects)
		B(SE)	OR(95% CI)	P value	B(SE)	OR(95% CI)	P value
Job	Housewife	Reference Group
	Employed	0.032(0.39)	1.03(0.47–2.24)	0.936	0.20(0.45)	1.22(0.50–2.98)	0.658
Education	Elementary	Reference Group
	High school	0.24(0.42)	1.27(0.56–2.91)	0.561	0.33(0.43)	1.39(0.59–3.23)	0.443
	University	0.08(0.45)	1.09(0.44–2.65)	0.852	0.04(0.48)	1.04(0.40–2.70)	0.930
Location	City	Reference Group
	Village	–0.04(0.25)	0.96(0.59–1.57)	0.881	0.01(0.026)	1.01(0.60–1.71)	0.960
history of stillbirth	No	Reference Group
	Yes	1.82(0.92)	6.25(1.02–37.71)	0.048	1.91(0.94)	6.80(1.07–43.00)	0.042
Delivery	C.S	Reference Group
	NVD	–0.32(0.25)	0.72(0.43–1.19)	0.209	–0.31(0.26)	0.73(0.43–1.22)	0.236
Gestational Diabetes	No	Reference Group
	Yes	1.25(0.62)	3.48(1.04–11.73)	0.044	1.27(0.63)	3.58(1.03–12.37)	0.044
Preterm labor	No	Reference Group
	Yes	–0.35(0.37)	0.70(0.34–1.45)	0.342	–0.64(0.51)	0.52(0.19–1.43)	0.208
admitted to NICU	No	Reference Group
	Yes	0.02(0.33)	1.02(0.52–1.99)	0.946	–0.04(0.46)	0.96(0.38–2.41)	0.934
First-minute APGAR score	7≤	Reference Group
	7>	0.45(0.54)	1.57(0.54–4.55)	0.402	0.38(0.90)	1.46(0.25–8.52)	0.673
Fifth-minute APGAR score	7≤	Reference Group
	7>	0.89(0.74)	2.45(0.57–10.49)	0.226	0.82(1.08)	2.27(0.26–19.15)	0.451
Age (years)	–	0.014(0.018)	1.01(0.97–1.05)	0.455	0.01(0.02)	1.01(0.97–1.05)	0.514
BMI(kg.m2)	–	0.02(0.03)	1.02(0.95–1.08)	0.609	0.01(0.03)	1.01(0.94–1.08)	0.695
Birth weight (kg)	–	0.07(0.18)	1.07(0.74–1.54)	0.698	–0.08(0.27)	0.91(0.54–1.55)	0.752

NVD, normal vaginal delivery; S.C, caesarean section; SE, Standard error; APGAR, appearance, pulse, grimace, activity, and respiration; BMI, Body mass index.

Regarding the incidence of adverse perinatal outcomes, 29 women (7.2%) had preeclampsia, 8 women (2%) had gestational hypertension, 64 women (16%) had preterm labor in the 28th to 37th week of pregnancy, 71 women (17.8%) had gestational diabetes, and 37 women (9.3%) experienced abnormal fetal heartbeat during labor. At the time of birth, 16 cases (4%) were underweight according to the weight of the fetus based on the gestational age. Sixty-four neonates (16%) were admitted to the NICU after birth. The fifth-minute Apgar score of 8 babies (2%) was less than 7, and the first-minute Apgar score of 18 babies (4.5%) was less than 7. The results showed that gestational diabetes has a significant association with abnormal UCI in regression analysis (P = 0.044). After considering the maternal age, BMI, job, and education (adjusted effects), women with gestational diabetes had a 3.58 times higher chance of abnormal UCI than other subjects (Table 4).

In the regression model, no significant association was found between abnormal UCI and the first- and fifth-minute Apgar scores. However, neonates with first- and fifth-minute Apgar scores less than or equal to 7 were 1.6 and more than 2 times more likely to have abnormal UCI than others, respectively. No significant association was observed between birth weight and abnormal UCI (P = 0.628). Other neonatal and fetal variables, including abnormal fetal heart rate during labor, preterm labor, and admissions to NICU, did not have a significant association with abnormal UCI.

4 Discussion

One of the main findings of this study was that the presence of diabetes had a significant association with abnormal UCI; thus, the probability of abnormal UCI was about 3.5 times higher after adjusted effects. This finding is consistent with the study by Chitra et al., who measured postpartum UCI and determined its association with maternal and fetal outcomes. They demonstrated that hyper coiling had a significant association with gestational diabetes [2]. In addition, in the study by Najafi et al., umbilical vessel hypo coiling was significantly more common in gestational diabetes [1]. However, this is inconsistent with the study by Chen et al., in which diabetes had no significant association with abnormal UCI [13]. Diabetes as a metabolic disease may cause abnormal UCI by damaging the umbilical vessels and the connective tissue components of Wharton’s jelly, which plays a role in the main structure of the umbilical cord, justifying this association [1].

In the present study, no significant association was found between gestational blood pressure and preeclampsia with UCI. However, in the study by Chitra et al., blood pressure abnormalities were significantly associated with hypo coiling [2]. Milani et al. conducted a study to measure postpartum UCI and determine its association with adverse perinatal outcomes, indicating that abnormal UCI was associated with gestational blood pressure and preeclampsia [3].

In Milani et al.’s study, the cases of preeclampsia and eclampsia that were mostly candidates for emergency cesarean delivery and could affect the results were not analyzed because they excluded them from the study. Moreover, the umbilical cord, probably because of its elastic properties, can resist external forces, coiling, and stretching; in addition, umbilical cord coiling is not affected by blood pressure.

In the current study, no association was found between LBW and UCI, which is in line with a study [14] that examined the predictive value of UCI. However, Chen et al. found that LBW was significantly associated with umbilical cord coiling [13]. Nevertheless, in Milani et al.’s study, no significant association was found between birth weight and UCI [3]. The available studies in this regard are not in the same direction.

Pergialiotis et al., in a meta-analysis study, emphasized the association between UCI abnormalities and adverse pregnancy outcomes. However, they recommended that more studies are needed to show whether the UCI assessment can be used as a program in uncomplicated pregnancies [15].

In our study, no significant association was found between UCI and first- and fifth-minute Apgar scores, but the frequency of hypo-coiled cases was higher in infants whose fifth-minute Apgar score was <7. This finding was not significant compared with normal- and hyper-coiled cases, which is consistent with other studies [3, 13]. However, Sahoo K et al., in a study aimed to relate the significance of the umbilical coiling pattern in the UCI to different fetal parameters, showed that the first-minute Apgar score <4 and fifth-minute Apgar score <7 were significantly associated with hypo-coiled umbilical cords [6].

Our results showed an association between UCI and abnormal fetal heart rate during labor, indicating no significant relationship. However, in a study, fetal heart rate abnormalities during labor were much higher in patients with umbilical cord coiling [13].

However, Milani et al. indicated that abnormal UCI was associated with adverse outcomes, such as abnormal heart rate [3]. Further, Rabiee et al. showed a significant association between a delayed decrease in fetal heart rate and hypo coiling [16].

In addition, Chitra et al. found a significant association between abnormal fetal heart rate (prolonged drop and tachycardia) and both hyper coiling and hypo coiling [2]. Perhaps our sample size was insufficient to obtain this result.

In line with Milani et al., our results indicated no significant association between abnormal UCI and hospitalization in the NICU [3]. However, Chen et al. showed that admission to the NICU was significantly associated with umbilical cord coiling [13].

According to the present study, a history of stillbirth was significantly associated with abnormal umbilical cord coiling. Hammad et al. conducted a study on women with and without a history of multiple stillbirths, in which abnormal umbilical cord coiling was one of the anomalies. Ultimately, they concluded that a low UCI score was generally associated with stillbirth. Accordingly, since there is no gold standard to definitively determine the cause of stillbirths, umbilical cord abnormalities could be associated with stillbirths, but it is impossible to be certain that the umbilical cord abnormality was the definitive cause of death of the fetus [17].

In the present study, no relationship was found between the delivery method (cesarean or vaginal) and abnormal UCI. However, in the study by Chen et al., cesarean delivery, vaginal delivery with instruments, and emergency cesarean delivery were significantly higher in patients with umbilical cord coiling [13]. In the study by Chitra et al., no significant relationship was observed between instrumental deliveries and umbilical cord coiling, but hyper coiling was significantly associated with cesarean sections [2].

In general, in the current study, there was no significant association between demographic characteristics (maternal age and maternal BMI) and fertility characteristics (number of pregnancies, previous miscarriages, and previous macrosomic birth) with abnormal UCI, but in the study by Chen et al., umbilical cord coiling was found to be significantly more common in patients with maternal age greater than 35 years [13]. According to the study, most pregnancies with hyper- or hypo-coiled umbilical cords can have normal outcomes. Currently, it is recommended that perinatal pathologists and clinicians continue to record and review clinical features associated with abnormal cord coiling patterns; however, based on currently available data, one should be cautious about determining the cause of an adverse outcome based on UCI alone.

Every study has strengths and limitations. One of the strengths of this study is that it is a longitudinal and prospective study. However, a limitation of this study is the lack of UCI ultrasonography in the second and third trimesters of pregnancy; this is because pregnant women were less likely to visit Rouhani Hospital for prenatal care at the time of the study due to the COVID-19 pandemic. This is because this hospital was a center for hospitalized COVID-19 patients. Therefore, it is recommended that UCI be determined by ultrasound starting in the second or third trimester of pregnancy and that UCI be determined after delivery, and its association with adverse pregnancy outcomes be investigated. The small sample size in the study is considered a major limitation. This limitation can be solved by conducting large and multi-center studies.

5 Conclusions

Gestational diabetes is significantly associated with abnormal coiling of the umbilical cord. Also, the history of stillbirth has a significant association with abnormal coiling of the umbilical cord. Furthermore, more studies are needed to accurately determine the relationship between umbilical cord coiling and clinical outcomes. According to the results, it is recommended to perform a UCI examination after delivery as part of a neonatal examination to find an explanation for perinatal morbidity and mortality.

Footnotes

Acknowledgments

The authors would like to thank Babol University of Medical Sciences for the funding and supervision of the study. We are grateful to all the physicians and midwives of the Rohani Hospital of Babol, who have done a lot of work to collect information. We also thank the pregnant women who participated in this study.

Disclosures

Human subjects: Consent was obtained or waived by all participants in this study. The Ethics Committee of Babol University of Medical Sciences issued approval IR.MUBABOL.REC.1399.210.

Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue

Competing interests: The authors declare no competing interests.

Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work.

Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work.

Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Author contributions

F.NA and Z.H contributed to the conception of the study. F.NA, Z.H, M.J, Z.P, and H.A.N contributed to the design of the study and development of the search.

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