Umbilical Cord Abnormalities

Sara M. Seifert

OVERVIEW

Peripartum umbilical cord management can have profound maternal and fetal effects from preventing asphyxia, hemorrhage, and long-term morbidity to promoting neonatal and maternal well-being. It is imperative for the emergency provider to have an understanding of normal umbilical cord management as well as possible umbilical cord anomalies and emergencies such as nuchal or entangled umbilical cords, severed umbilical cords, umbilical cord prolapse, short umbilical cords, velamentous cord insertion, and vasa previa. There are additional conditions of the umbilical cord that may be encountered including vascular abnormalities (such as a single artery or aneurysm), cysts, hematomas, teratomas, and knots but they are not generally managed in the emergency setting.¹

ANATOMY

The normally developed umbilical cord contains two arteries and one vein surrounded and supported by Wharton’s jelly, a gelatinous white/translucent tissue (Figure 25.1).² The length of the umbilical cord can be highly variable, with a mean length of 32 cm at 20 weeks’ gestation and 60 cm at 40 weeks’ gestation, with a range between 35 and 80 cm at term.³ Longer umbilical cords pose increased risk of forming knots, nuchal or entangled cords, as well as prolapsing through the cervix. Umbilical cords less than 35 cm are associated with placental abruption, poor fetal growth, decreased fetal activity in utero, and developmental abnormalities. Umbilical thickness can range from 1.5 to 3.6 cm, with thinner cords being more prone to tearing or occlusion. A single uterine artery is present in approximately 2 to 6 per 1,000 live births. It is an isolated finding in 70% to 80% of neonates; however, in 20% to 30% it is associated with congenital anomalies such as cardiovascular, gastrointestinal, renal, and central nervous system, as well as chromosomal abnormalities.⁴ The frequency of various umbilical cord abnormalities seen at birth is shown in Table 25.1.

Figure 25.1: Normal umbilical cord anatomy.

TABLE 25.1 Frequency of Umbilical Cord Abnormalities

Abnormalities	Frequency
Nuchal/entangled cord	15%-34%⁵
Cord prolapse	16-18 in 10,000 live births^6,7,8,9,10
Vasa previa	1 in 2,500 deliveries¹¹
Velamentous cord insertion	1% of singleton gestations and up to 15% of monochorionic twin gestations¹²
Knots	1.3%^1,10

NORMAL FULL-TERM DELIVERY CORD MANAGEMENT

After delivery of the neonate’s head, the mother should be instructed to stop pushing for a moment to allow for external rotation or restitution of the baby’s head and for assessment of a nuchal cord (where the umbilical cord is wrapped around the neck) by palpating the fetal neck. If the mother does not have an epidural, or she feels a significant amount of pelvic pressure, she may not be able to stop pushing and will continue to push toward delivery.

In the absence of maternal or neonatal complications, after the delivery of a healthy term infant, the provider should visually assess the umbilical cord length. If the umbilical cord is perceived to be short, meaning that the neonate cannot be moved away from the perineum without putting tension on the umbilical cord, then care must be taken to keep the neonate close to the perineum while clamping and cutting the cord. If there is enough length to the umbilical cord, then the neonate should be placed skin-to-skin on the mother’s abdomen or chest to promote bonding and minimize heat loss of the neonate before cord clamping. If the neonate appears to need further resuscitation, the umbilical cord can be clamped and cut to facilitate evaluation.

Delayed Cord Clamping

The decision to delay cord clamping at term has been an active area of research, with recent changes in management guidelines. After birth, spontaneous respirations in the infant occur after
10 to 15 seconds with the subsequent transition from fetal to neonatal circulation. Approximately 75% of the blood available for placenta-to-neonate transfusion is transferred in the first minute after birth.¹³

A meta-analysis randomizing infants to either immediate or late (defined as 2-3 minutes after birth) cord clamping found late cord clamping results in higher hemoglobin levels by a mean of 1.49 g/dL in 24 to 48 hours after birth and 8% had iron deficiency at 3 to 6 months of age compared to 14% in the immediate cord clamping group. Late cord clamping results in more neonates requiring phototherapy versus early cord clamping. Another trial followed children with early versus late cord clamping for 4 years and found possible improved neurodevelopmental outcomes, particularly in boys, and no harmful effects.²^,¹³^,¹⁴

The American College of Obstetrics and Gynecology (ACOG) and the American Academy of Pediatrics (AAP) recommend delaying cord clamping for 60 seconds after birth for vigorous infants that do not otherwise require resuscitation.

Advantages of delayed cord clamping: higher infant iron stores at 6 months and possible improved neurodevelopmental outcomes²^,¹³^,¹⁴
Disadvantages of delayed cord clamping: hyperbilirubinemia in the immediate newborn period requiring phototherapy or an exchange transfusion. Notably, if cord blood is to be collected, delayed cord clamping may not allow for an adequate sample¹⁴
Contraindications to delayed cord clamping: Placental abruption, placenta previa, as well as cord avulsion, as these conditions can cause loss of fetal blood and severe fetal anemia¹⁴

In general, milking the umbilical cord—where the provider uses their hand to gently push blood from the cord into the neonate—is not done in full-term neonates, although it could be an alternative practice to delayed cord clamping if the cord must be clamped quickly for maternal or neonatal resuscitation. Cord milking will increase preload to the neonate and increase hemoglobin levels; however, it has not been found to reduce hypotension, need for a blood transfusion, requirement for inotropes, or necrotizing enterocolitis rates.

The umbilical cord should be clamped on both the fetal and maternal sides, a minimum of 2 to 3 cm from the baby’s abdominal wall, and then cut with sterile scissors or a scalpel between the clamps, preferably using sterile gloves and an aseptic technique to prevent omphalitis (Figure 25.2). After delivery, the clamped umbilical cord of the newborn should be inspected for general appearance and the number of vessels.

Figure 25.2: Clamping and cutting of the umbilical cord.

Nuchal/Entangled Umbilical Cords

The umbilical cord may become entangled around any part of the fetus, with the neck being the most common site. A nuchal cord is when a loop or loops of umbilical cord are wrapped around the fetal neck and is a common finding at delivery with a frequency of 15% to 34%. It is associated with excessive movement or a long umbilical cord (>70-80 cm) and increasing gestational age.³ Single nuchal cords are more common than multiple nuchal cords (11% to 28% vs. 2% to 7%).

In most cases, it is not associated with adverse fetal outcome and intrapartum complications; however, the effect on pregnancy outcomes is still controversial. When nuchal cords are tight (6.6% of live births), they can lead to fetal asphyxia or tearing of the cord, which can potentially lead to fetal hemorrhage. Nuchal cords may also be associated with impaired fetal growth (although studies have had discordant findings), meconium-stained amniotic fluid, fetal thrombotic placental vasculopathy, intrapartum fetal heart rate abnormalities, operative delivery, low 5-minute Apgar scores, and acidemia.⁵ An ultrasound of the fetal neck, with or without Doppler, may show a nuchal cord, although a cord lying across the neck, a neck mass, or fetal skin folds may appear similar to a nuchal cord. In general, screening for the presence of a nuchal cord prior to delivery is not done as it will not in itself change the mode of delivery or labor management.

As the fetal head descends and rotates through the pelvis, the tightness of the nuchal cord may change and subsequently result in decreased fetal heart rate variability or prolonged decelerations, which should be managed accordingly. After delivery of the head, the mother should be instructed to stop pushing for a moment to allow for external rotation/restitution of the baby’s head and for assessment of a nuchal cord by palpating the fetal neck.

Loose Nuchal Cord

A loose nuchal umbilical cord(s) can be easily and gently slipped over the fetal head by the provider.

Management

Gently slip the umbilical cord over the fetal head, being careful not to put tension on the cord that could cause tearing of the umbilical cord (Figure 25.3). Once the cord is reduced, the mother may start pushing again, with subsequent delivery of the neonate as usual.⁵

Tight Nuchal Cord

A tight nuchal umbilical cord is too tight around the fetal neck to easily slip over the fetal head.

Management

The cord may either be doubly clamped and cut to allow delivery or the neonate can be delivered without reducing the umbilical cord (referred to as “delivering through the cord”). Given the risk of avulsing the cord, most providers prefer to clamp and cut the cord. Two Kelly clamps may be slipped on the cord and the cord cut in between (Figure 25.4). This will usually result in freeing of the neonate to deliver.⁵ If there is concern for a shoulder dystocia, it is reasonable to wait until after the anterior shoulder delivers to clamp and cut the umbilical cord if possible to maximize perfusion to the neonate should a delay in delivery occur.

If the cord is too tight to reduce or clamp or if the neonate is delivering quickly, then the provider can deliver the neonate with the nuchal cord(s) in place. It is recommended to avoid putting too much traction on the cord so as not to avulse or tear the cord. One can accomplish this by keeping the fetal head close to the mother’s pubic bone or inner thigh, which allows the shoulders and then the body to deliver in a somersault motion (Figure 25.5).⁵ After delivery, the cord can then be unwrapped.

Severed Umbilical Cord

A severed umbilical cord refers to a partial or complete tearing of the umbilical cord. In this scenario, the bleeding from the fetal side will be fetal blood. Given that neonates have a relatively small blood volume (80-90 mL/kg of blood in a term infant and 90-100 mL/kg in a preterm infant) neonates can exsanguinate quickly.