Association of Length of Umbilical Cord and Fetal Outcomes

The umbilical cord is a fundamental anatomical structure that joins fetus to placenta and plays a critical role in maintaining the fetal life during the pregnancy. It functions as primary channel for oxygen and nutrients transfer between the maternal and fetal circulations. Umbilical cord typically encompasses two umbilical arteries and one umbilical vein entrenched within the protective mucoid connective tissue. Any disruption in morphology or dimensions of umbilical cord may compromise the fetal safety and results in the adverse perinatal outcomes 1-3.

Among the several morphological cord characteristics, its length has gained the considerable attention in the obstetric research due to its potential impact on the pregnancy outcomes. Cords shorter than 40 cm are usually considered as short whereas those surpassing 80 cm are categorized as long. Both extremes cord length are linked to the neonatal morbidity. Short cords may limits the fetal movement and sometime leads to fetal distress, however markedly long cords may affect to cord entanglement and prolapse 4-6. Complications may eventually present as low Apgar scores, NICU admissions or perinatal mortality 7. A study demonstrated that abnormal umbilical cords lengths were associated with the amplified rates of fetal heart rate irregularities and operative deliveries during the labour. Abnormal cord length was associated to higher frequencies of birth asphyxia in comparison to normal cords length 8. Evidence demonstrated that abnormal cord length is also associated with fetal distress and prolonged labour more commonly when cord length deviates from the normal range 9. A Pakistani study reported that abnormal cords were associated with a higher incidence of stillbirth and birth asphyxia in comparison to normal length cords. Such findings highlighted the significance of cord characteristics when evaluating fetal health during the labour 10. Emerging research has emphasized the significance of examining the umbilical cord abnormalities as part of routine obstetric evaluation. Morphological variations of cord may reflect the fundamental placental dysfunction and may consequently serve as indicator of compromised fetoplacental circulation. Early recognition of abnormalities may assist the clinicians to identify pregnancies at greater complications risks and implement suitable surveillance policies.⁹.¹⁰

Given the potential impact of abnormal cord length on fetal wellbeing. A better understanding of its association with the perinatal outcomes is vital for improving the obstetric care. Evaluating such association may assist the clinicians in anticipating intrapartum complications, guiding timely intervention and eventually reducing the neonatal adverse outcomes. This present study aims to evaluate the association between umbilical cord length and fetal outcomes to provide the evidence that may contribute to better maternal and neonatal care.

The study enrolled 100 pregnant women. The median maternal age was 28 years (22 to 33 years) (Table I).

Table II presents the distribution of patients according to the length of umbilical cord. A short cord was observed in 16 cases (16.0%). The majority of women, 73 (73.0%) had a normal cord. A long cord was found in 11 cases (11.0%) (Table II). In the present study caesarean section was performed in 19% (n = 19) patients, while 81 (81%) neonates were delivered normally.

Table III presents the fetal outcomes of the study population.

Table IV presents the association of fetal outcomes with the length of umbilical cord. Neonates with short cords 4 (25.0%) had a lower Apgar score, while 3 (4.1%) neonates in the normal cord group had lower APGAR score. Five (45.5%) of those with long cords had a low Apgar score (p < 0.001).

Two stillbirths (12.5%) occurred in the short cord group, while one (1.4%) in the normal cord group and 3 stillbirths (27.3%) in the long cord group (p = 0.003). In short cord group neonates 5 (31.2%) neonates required admission, while 6 (8.2%) in the normal cord group. In the long cord group 3 neonates (27.3%) were admitted to NICU (p = 0.019). Similarly Low birth weight was more common in the short and long cord group (p =0.021). Fetal distress on CTG was also associated with short and long cord groups (p = 0.014).  Nuchal cord loops were present in only 1 (6.2%) of the short cord group and 8 (11.0%) of the normal cord group, while in 6 cases (54.5%) in the long cord group (p = 0.002).

Table I    Baseline parameters

Table II    Distribution of umbilical cord length

Table III     Fetal outcomes

Table IV     Association of umbilical cord length with fetal outcomes

The findings of the present study revealed that both short and long umbilical cords were significantly associated with adverse fetal outcomes, The normal cord length group consistently exhibited the most favourable outcomes across all parameters.

The prevalence of short cords in this study was 16.0% (n = 16), while long cords were observed in 11.0% (n = 11) cases. In a recent study by Akhtar et al. conducted in Peshawar, short cords were found in 9.8% and long cords in 17.65% of their sample.13 The slightly higher proportion of long cords in their study may be attributed to differences in sample size and population characteristics. Another study by Mehr et al. from Peshawar reported short cords in 21.6% and long cords in 7.5% of their patients, using a slightly different cut-off values of less than 35 cm for short cords and more than 80 cm for long cords.14 The variation in prevalence across studies can be attributed to the definitions used for cord length categories.

Regarding low Apgar scores, the present study found that 25.0% (n = 4) of neonates with short cords and 45.5% (n = 5) with long cords had scores below 6 at five minutes. These findings align with Shafqat et al. who reported low Apgar scores in 30.64% of the short cord group and 23.89% of the long cord group in their large scale study of 3,300 deliveries.10 Akhtar et al. observed low Apgar scores in 40% of the short cord group and 25.9% of the long cord group.13 The consistency of these findings across multiple studies conducted in similar settings validates the evidence that abnormal cord length compromises neonatal wellbeing at birth.

Stillbirth was another outcome of interest in the present study, with rates of 12.5% (n = 2) in the short cord group and 27.3% (n = 3) in the long cord group, while only one case 1.4% in the normal cord group. Shafqat et al. also reported higher stillbirth rates at both extremes of cord length, with 11.29% in the short cord group and 12.57% in the long cord group.10 Hayes et al. in their analysis reported that multiple nuchal loops are commonly associated with associated with significantly increased risk of stillbirth.15

NICU admission was required for 31.2% (n = 5) of neonates with short cords and 27.3% (n = 3) of those with long cords. These findings are consistent with those of Mehr et al. who reported NICU admission rates of 31.0% in the short cord group and 20.0% in the long cord group.14 Kulshrestha et al. also found significantly higher NICU admission rates in the presence of cord abnormalities, further validating the association between cord length and neonatal morbidity.16

The study also found that Low Birth Weight was more common in short and long umbilical cord group as compared to normal cord length. This pattern is consistent with the findings of Mehr et al, who reported low birth weight in 41.4% of their short cord group and 20.0% of their long cord group.14 The association between short cords and low birth weight may reflect the shared underlying factors that restrict both fetal growth and cord elongation such as reduced fetal movement or intrauterine constraint. Fetal distress in the presents was also associated with the short and long umbilical cord length. Shafqat et al, reported fetal heart rate abnormalities in 48% of the short cord group and 47% of the long cord group. 10

Nuchal cord loops were present in 54.5% (n = 6) of the long cord group, compared to only 6.2% (n = 1) of the short cord group and 11.0% (n = 8) of the normal cord group. Shiva Kumar et al, reported that the incidence of nuchal cord increases significantly with cord length reaching 70% in their long cord group. 17 Studies have shown that long cords are strongly associated with nuchal entanglement and adverse fetal outcomes, including fetal distress, arrest of descent, and perinatal death, with the risk increasing further when knots are also present..18-20

The present study demonstrates that both extremes of cord length are associated with poorer fetal outcomes. This highlights the concept that the umbilical cord is an active determinant of fetal wellbein and deviations from normal length warrant clinical attention.

Several limitations of this study must be acknowledged. The sample size of 100 patients is relatively modest for such study, which may limit the precision of the estimates. The study was conducted in a single tertiary care setting, which may limit generalisability to other settings. Future research with larger, multicentre samples are required to address the underlying mechanisms and inform strategies for early intervention.

In conclusion, the present study demonstrated that deviations from normal umbilical cord length were associated with adverse fetal outcomes. Short and long umbilical cords were associated with higher rates of low Apgar scores, stillbirth, NICU admission, low birth weight, fetal distress and nuchal cord loops compared with normal length umbilical cords. Future research with larger, multicentre samples are required to address the underlying mechanisms and inform strategies for early intervention.