The placenta begins developing at the site of implantation by the fifth week of gestation, with a typical thickness of 2.5 cm and a weight of around 500 grams. It consists of a maternal surface divided into cotyledons and a foetal surface called the chorionic plate, with the umbilical cord inserted centrally. Placental growth occurs in two stages, with rapid growth before 12 weeks and equal growth with the foetus after 17 weeks, reaching a weight of one-sixth of the foetal weight at term¹. The placenta is a vital materno-foetal organ that supports endocrine, immunological, excretory, respiratory, and nutritional functions, facilitating the exchange of nutrients, oxygen, and waste products between maternal and foetal circulation². It also protects the foetus by preventing immune attacks and blocking the transfer of harmful microorganisms from the mother.Usually during ultrasound, placenta is evaluated by its position and morphological changes. Placenta is the reflection of the health of the foetus. Based on its morphological changes like abnormal shape, size and growth pattern we can detect antenatal complications like maternal gestational diabetes, intra uterine growth restriction, foetal hydrops³.

The umbilical cord is a vital structure connecting the foetus to the placenta, facilitating the flow of oxygenated, nutrient-rich blood to the foetus and returning deoxygenated blood back to the placenta. Composed of two umbilical arteries, one umbilical vein, Wharton's jelly, and an outer layer of amnion, it protects the blood vessels and ensures blood flow with its helical coiling. Appearing by the fourth week of gestation, the cord is typically 50-60 cm long at term, crucial for foetal survival and development⁴. Routine antenatal sonographic evaluations often assess the number of umbilical vessels, with some sonologists performing Doppler assessments of blood flow. Alterations in the umbilical cord's constitution or metabolism can be linked to conditions like IUGR, preeclampsia, PIH, diabetes, and foetal distress⁵, making it a predictor for adverse maternal and fetal outcomes⁶. However, there is limited literature on the morphological studies of the normal umbilical cord, which is particularly vulnerable to damage as it floats freely in the amniotic fluid.A lean umbilical cord was reported to be associated with small-for gestational-age (SGA) neonates by Raio and colleagues⁷. Goynumer et al, found significant differences in mean gestational age, mode of delivery, birth weight, and adverse perinatal outcome between foetuses with umbilical cord thickness below the 5th centile (lean umbilical cord) vs. those with umbilical cord thickness above the 5th centile (non-lean cord) in the first and early second trimesters of gestation⁸. In a study on foetuses with sonographically measured low umbilical cord cross-sectional area, Ghezzi et al, found a significant relationship between umbilical vein cross-sectional area below the 10th percentile and adverse neonatal outcome⁹. Sonographic measurements of the umbilical cord, including diameter and cross-sectional area, increase with gestational age, with significant changes observed in the diameters of the umbilical artery and vein as pregnancy progresses. Structural abnormalities of the umbilical cord, such as excessive coiling, single umbilical artery, and vasa previa, can lead to adverse outcome¹⁰, while advancements in imaging technologies like Doppler and 3D sonography have improved the assessment of these conditions¹¹. Despite these innovations, current screening and diagnostic methods for detecting foetal compromise and preterm birth still face limitations, leading to potential overdiagnosis and unnecessary interventions.

AIM

To evaluate the relationship of umbilical cord thickness and cross sectional area with foetal outcome.

This study was designed as a cross-sectional observational study conducted at the Department of Obstetrics and Gynaecology, PBM Hospital, Bikaner. The study was carried out over a one-year period, starting in January 2024 and continuing until the required sample size was achieved. The study population included pregnant women in their third trimester, specifically between 32 and 36 weeks of gestation, who were either admitted to the hospital or attended the outpatient department (OPD) of the Obstetrics and Gynaecology Department at the hospital. Inclusion criteria for the study included women with singleton pregnancies, regardless of parity, and those with a reliable gestational age of 32 to 36 weeks as determined by sonography. Only women aged 18 years or older who were willing to participate in the study were included. Exclusion criteria consisted of women with multiple pregnancies, lethal fetal congenital anomalies, or those who could not be followed through to delivery for any reason. Additionally, patients who declined to provide consent were also excluded from the study.

A sample size of 300 pregnant females required 80% study power and alpha error 5%. Prevalence of poor outcome in hypercoiled cord in pregnant women is 73.3% as per reference article.14

Alpha 5% 

Beta 20%

Power of study -80%

N =4 pq/l2

A sample size of 300 cases was taken including fulfilling the eligibility criteria.  

TABLE 1: Distribution of cases according to Age

Out of 300 cases maximum 180 (60.00%) cases were in 19 – 25 yr age group followed by 30.00% in 26 – 30 yrs whereas minimum 2.67% were in >35 yrs age group followed by 7.33% in 31 – 35 yr group. Mean age was 24.55 ± 5.6 yr.

Graph1: Distribution of cases according to their Gravida and mode of Delivery

60.67% cases were primipara whereas 39.33% were multipara. 60.67% cases were normal vaginal delivery whereas 39.33% were LSCS.

TABLE 2: Distribution of cases according to their umbilical cord thickness

Maximum 78.33% cases were in 10th to 90th centile of umbilical cord thickness followed by <10 centile were 16.67% whereas minimum 5.00% were >90th centile of umbilical cord thickness. 

TABLE 3: Distribution of cases according to their umbilical cord cross sectional area

Maximum 78.00% cases were in 10th to 90th centile of umbilical cord cross sectional area followed by <10 centile were 17% whereas minimum 5.00% were >90th centile of umbilical cord cross sectional area. 

TABLE 4: Association of umbilical cord thickness with outcome

Out of 51 MSL cases, 62.75% were in the <10th percentile of umbilical cord thickness, 33.33% in the 10th to 90th percentile, and 3.92% in the >90th percentile; whereas, out of 249 normal cases, 87.55% were in the 10th to 90th percentile, 7.23% in the <10th percentile, and 5.22% in the >90th percentile.

TABLE 5: Distribution of cases according to their umbilical cord cross sectional area with outcome

Out of 51 MSL cases, 60.78% were in the <10th percentile of umbilical cord cross-sectional area, 35.29% in the 10th to 90th percentile, and 3.92% in the >90th percentile; whereas, out of 249 normal cases, 86.75% were in the 10th to 90th percentile, 8.03% in the <10th percentile, and 5.22% in the >90th percentile.

TABLE 6: Association of umbilical cord thickness with APGAR

Out of 24 cases with APGAR <7 at 5 minutes, 54.17% were in the <10th percentile of umbilical cord thickness, 41.67% in the 10th to 90th percentile, and 4.17% in the >90th percentile; whereas, out of 276 cases with APGAR >7, 81.52% were in the 10th to 90th percentile, 13.41% in the <10th percentile, and 5.07% had umbilical cord thickness in the >90th percentile.

TABLE 7: Association of umbilical cord cross sectional area with APGAR

Out of 24 cases with APGAR <7 at 5 minutes, 54.17% were in the <10th percentile of umbilical cord cross-sectional area, 41.67% in the 10th to 90th percentile, and 4.17% in the >90th percentile; whereas, out of 276 cases with APGAR >7, 81.16% were in the 10th to 90th percentile, 13.77% in the <10th percentile, and 5.07% in the >90th percentile.

Graph 2: Association of umbilical cord thickness and cross sectional area with NICU admission

In the study, among infants with a cross-sectional area <10th percentile, 15 (55.56%) required NICU admission, while 36 (13.19%) did not; among those with a cross-sectional area between the 10th and 90th percentiles, 10 (37.04%) were admitted to the NICU, and 224 (82.05%) were not; and among those with a cross-sectional area above the 90th percentile, 2 (7.41%) required NICU admission, while 13 (4.76%) did not, with a highly significant p-value of 0.0001; similarly, among infants with cord thickness <10th percentile, 14 (51.85%) were admitted to the NICU, while 36 (13.19%) were not; among those with cord thickness between the 10th and 90th percentiles, 12 (44.44%) required NICU admission, and 223 (81.68%) did not; and among those with cord thickness above the 90th percentile, 1 (3.70%) required NICU admission, while 14 (5.13%) did not, with a highly significant p-value of 0.0001.

Graph 3: Association of umbilical cord thickness with birth weight and  umbilical cord cross sectional area

In the study, among infants with weight <2.5kg, 33 (61.11%) were below the 10th percentile, 21 (38.89%) were between the 10th and 90th percentile, and none were above the 90th percentile, while among those with weight >2.5kg, 18 (7.32%) were below the 10th percentile, 213 (86.59%) were between the 10th and 90th percentile, and 15 (6.10%) were above the 90th percentile, with a highly significant p-value of 0.0001; similarly, among infants with weight <2.5kg, 32 (59.26%) had cord thickness below the 10th percentile, 22 (40.74%) had cord thickness between the 10th and 90th percentile, and none had cord thickness above the 90th percentile, while in the >2.5kg group, 18 (7.32%) had cord thickness below the 10th percentile, 213 (86.59%) had cord thickness between the 10th and 90th percentile, and 15 (6.10%) had cord thickness above the 90th percentile, with a p-value of 0.0001.

In our study, out of 300 cases maximum 180 (60.00%) cases were in 19 – 25 yr age group followed by 30.00% in 26 – 30 yrs whereas minimum 2.67% were in >35 yrs age group followed by 7.33% in 31 – 35 yr group. Mean age was 24.55 ± 5.6 yr. Similarly Saswati Sanyal Choudhury et al. (2023)¹² found that the mean age was found to be 25.57 with a SD of 3.174, the minimum age being 19 years and maximum age was 34 years.

In our study, 60.67% cases were primipara whereas 39.33% were multipara, 60.67% cases were normal vaginal delivery whereas 39.33% were LSCS

In our study, maximum 78.33% cases were in 10th to 90th centile of umbilical cord thickness followed by <10 centile were 16.67% whereas minimum 5.00% were >90th centile of umbilical cord thickness. Similarly  Monojit Chakrabarti et al. (2015)¹³ found that Out of 139 patients, 16 have lean cord, 112 patients have normal cord thickness and 11 patients have thick cords.

In our study, maximum 78.00% cases were in 10th to 90th centile of umbilical cord cross sectional area followed by <10 centile were 17% whereas minimum 5.00% were >90th centile of umbilical cord cross sectional area. Also Saswati Sanyal Choudhury et al. (2023)¹² found that In the study, 30(6%), 447(89.4%) and 23(4.6%) were 90th percentile of umbilical cord thickness.

In our study, out of 51 MSL cases maximum 62.75% cases were in <10 centile of umbilical cord thickness followed by 10th to 90th centile were 33.33% whereas minimum 3.92% MSL were in >90th centile of umbilical cord thickness. Out of 249 normal cases maximum 87.55% cases were in 10th to 90th centile of umbilical cord thickness followed by 7.23% of normal cases had umbilical cord thickness of <10 centile whereas minimum 5.22% were in >90th centile. Similarly Jaiprakash Narayan et al. (2022)¹⁴ found that Oligohydramnios and meconiumstained liquor were found to be associated with the smaller umbilical cord diameter. (P < 0.01)

In our study, out of 51 MSL cases maximum 60.78% cases were in <10 centile of umbilical cord cross sectional area followed by 10th to 90th centile were 35.29% whereas minimum 3.92% MSL were in >90th centile of umbilical cord cross sectional area. Out of 249 normal cases maximum 86.75% cases were in 10th to 90th centile of umbilical cord cross sectional area followed by 8.03% of normal cases had umbilical cord cross sectional area of <10 centile whereas minimum 5.22% were in >90th centile. Similarly Eze Charles et al. (2014)¹⁵ found that the mean cord cross-sectional area is 201.6 + 139.5mm2. 

In our study, out of 24 cases with APGAR <7 at 5min. maximum 54.17% cases were in <10 centile of umbilical cord thickness followed by 10th to 90th centile were 41.67% whereas minimum 4.17% were in >90th centile of umbilical cord thickness. Out of 276 cases with APGAR >7 at 5 min. maximum 81.52% cases were in 10th to 90th centile of umbilical cord thickness followed by 13.41% were in <10th centile whereas minimum 5.07% of normal cases had umbilical cord thickness of >90th centile.

In our study, out of 24 cases with APGAR <7 at 5min, maximum 54.17% cases were in <10 centile of umbilical cord cross sectional area followed by 10th to 90th centile were 41.67% whereas minimum 4.17% cases with APGAR <7 were in >90th centile of umbilical cord cross sectional area. Out of 276 cases with APGAR >7 maximum at 5min,  81.16% cases were in 10th to 90th centile of umbilical cord cross sectional area followed by 13.77% of cases had umbilical cord cross sectional area of <10 centile whereas minimum 5.07% were in >90th centile. 

Out of 27 cases admitted in NICU maximum 51.85% cases were in <10 centile of umbilical cord thickness followed by 10th to 90th centile were 44.44% whereas minimum 3.70% were in >90th centile of umbilical cord thickness. Out of 273 cases with no NICU admission maximum 81.68% cases were in 10th to 90th centile of umbilical cord thickness followed by 13.19% were in <10th centile whereas minimum 5.13% of normal cases had umbilical cord thickness of >90th centile. 

Out of 27 cases with NICU admission maximum 55.56% cases were in <10 centile of umbilical cord cross sectional area followed by 10th to 90th centile were 37.04% whereas minimum 7.41% cases with NICU admission were in >90th centile of umbilical cord cross sectional area. Out of 273 cases with no NICU admission maximum 82.05% cases were in 10th to 90th centile of umbilical cord cross sectional area followed by 13.19% of cases had umbilical cord cross sectional area of <10 centile whereas minimum 4.76% were in >90th centile. Jaiprakash Narayan et al. (2022)¹⁴ showed that 127 newborns were admitted and 176 newborns not required admission. Total 15 newborns were expired, all these were associated with antenatal maternal risk factors and less thickness of umbilical cord

In our study, out of 54 cases with birth weight <2.5kg maximum 59.26% cases were in <10 centile of umbilical cord thickness followed by 10th to 90th centile were 40.74%. Out of 246 cases with birth weight >2.5kg maximum 86.59% cases were in 10th to 90th centile of umbilical cord thickness followed by 7.32% were in <10th centile whereas minimum 6.10% were in umbilical cord thickness of >90th centile. Similarly Monojit Chakrabarti et al. (2015)¹³ found that Out of 112 normal thickened cords, 105 have birth weights more than 2 kg and 7 have birth weights less than 2 kg, out of 11 thickened cords 7 have normal birth weight between 2 – 4 kg, but 2 have birth weight more than 4 kg. We have found that low birth weight babies are associated with umbilical cord thickness below 10th percentile.

Out of 54 cases of birth weight <2.5kg maximum 61.11% cases were in <10 centile of umbilical cord cross sectional area followed by 10th to 90th centile were 38.89%. Out of 246 cases of birth weight >2.5kg maximum 86.59% cases were in 10th to 90th centile of umbilical cord cross sectional area followed by 7.32% of cases had cross sectional area of <10 centile whereas minimum 6.10% were in >90th centile. This is in accordance with a previous study by Prabhcharan and Jarjoura¹⁶ who reported a significant relationship between the umbilical cord cross sectional area and neonatal birth weight.

Umbilical cord thickness and cross sectional area are easy to measure in a free loop of umbilical cord which can be included in the routine antenatal sonographic evaluation. It has been proved that abnormal cord indices such as umbilical cord thickness and cross sectional area are associated with adverse perinatal outcome. To conclude, a more robust study with a greater margin of sample size in a large ethnic group should be undertaken to evaluate and standardize cut offs for cord indices, so that these standard value can be incorporated in the routine screening protocol, so these pregnancies should be closely followed-up for the successful perinatal outcome.   

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