Although umbilical cord conditions don’t always harm your baby, it’s important to know that some can cause serious complications. This can happen either during pregnancy or after birth, so it’s important to get the care you need from your maternal fetal medicine specialist. The American College of Radiology (ACR), the American Institute of Ultrasound in Medicine (AIUM), and the American College of Obstetricians and Gynecologists (ACOG) provide guidelines for performance of obstetric ultrasound which recommend that, in the second and third trimesters, the umbilical cord should be imaged and the number of vessels in the cord should be documented— and the placental cord insertion site should also be documented when technically possible. Here’s what to know about the different types of umbilical cord conditions and what to expect.
What are umbilical cord conditions?
The umbilical cord connects you and your baby during pregnancy. It’s responsible for transferring food, oxygen, and waste to and from your baby. It’s made up of important blood vessels and is normally about 22 inches long. Umbilical cord conditions usually affect the umbilical cord’s length, connection, or position inside the womb. There are many different umbilical cord conditions that can affect you and your baby, so your maternal fetal medicine specialist can help you navigate the screening and treatment process.
Umbilical Cord Conditions That May Be Diagnosed in the Prenatal Period
Single umbilical artery (SUA)
This condition is where the umbilical cord is missing an artery. Although it’s slightly more common in multiple pregnancies, it happens in one to five percent of pregnancies depending on the population studies. It can be diagnosed in the first trimester but often is identified in the second trimester during a target fetal anatomical scan. If this condition is present, there’s a chance your baby may develop certain health problems. This can include genetic conditions as well as heart, kidney, and digestion concerns. If your maternal fetal medicine specialist detects a problem, they may recommend some tests like high-frequency ultrasound or amniocentesis so you can create the right treatment plan once your baby is born. Most experts don’t consider isolated SUA a high-risk factor for offering invasive fetal genetic studies. However, offering noninvasive conventional serum screening or a cell-free DNA screening test for trisomies 21, 18, and 13 is reasonable. Invasive diagnostic testing (karyotype with microarray) should be offered to women in whom additional fetal abnormalities are observed (like anatomic abnormalities or symmetric growth restriction) or the aneuploidy screening test is positive , given the increased risk of fetal genetic abnormalities in each of these settings. There is no consensus about sonographic screening for fetal growth restriction; however, most clinicians recommend serial growth assessment in the 3rd trimester. Studies have generally reported that long-term physical and neurologic development of children with isolated SUA is similar to that in unaffected children. In the only study addressing the recurrence of SUA in the following pregnancy, isolated SUA in the first pregnancy doubled the odds of having SUA in the second pregnancy, while SUA with associated malformations in the first pregnancy quadrupled the odds of SUA in the second pregnancy.
Velamentous cord insertion (VCI)
A VCI is characterized by membranous umbilical vessels at the placental insertion site; the remainder of the cord is usually normal. In this condition, the umbilical cord ends several centimeters from the placenta, at which point the umbilical vessels separate from each other and cross between the amnion and chorion membranes before connecting to the subchorionic vessels of the placenta. They can occur in approximately one percent of singleton gestations, but as many as 15 percent of monochorionic twin gestations. It’s more common when the placenta implants low in the uterus over the cervix; this is known as a placenta previa. Velamentous cords contain a SUA in approximately 12 percent of cases. If the membranous insertion is near the lower part of the uterus, evaluation for membranous vessels near the cervix should be performed as this is a condition called a vasa previa (VP). VCIs are associated with a high preterm delivery rate (37.5 percent) and increased perinatal risks, such as neonatal intensive care unit admissions, small for gestational age, and perinatal death. The mother is also at risk for complications, such as an increased risk for undergoing manual removal of the placenta (the frequency was 5.5 percent of cases in one study). There are no data from large or controlled studies on which to base management recommendations, but we suggest serial assessment of fetal growth, weekly antenatal testing with biophysical profiles starting at 36 weeks, and delivery by 40 weeks gestation. In general, we also recommend continuous intrapartum fetal heart rate monitoring to identify signs of severe cord compression or vessel rupture. Minimal traction on the umbilical cord after delivery of the infant by the practitioner assisting in the birth is advised in order to avoid avulsion of the umbilical cord from the placenta.
Vasa previa (VP)
Vasa previa happens when blood vessels from the placenta or umbilical cord cross over the cervix. By convention, the presence of aberrant blood vessels within 2 cm of the internal opening of the cervix is considered to have similar implications as vessels actually covering the internal opening of the cervix. This location can cause them to tear during labor because they are unprotected within the membranes. In this case, it can cause life-threatening bleeding or complications for your baby. Even though this condition is extremely rare (estimated to occur 1 in 2500 pregnancies) it should be detected through a high-frequency ultrasound before birth. The prevalence is increased with second-trimester low-lying placentas or placenta previa (even if subsequently resolved), bilobed or succenturiate lobe placentas in the lower uterine segment, assisted reproductive conception, and multiple gestations. If a VP is confirmed and persists into the third trimester, you’ll need a c-section at 35 to 36 weeks to avoid the possibility of labor. We agree with American College of Obstetricians and Gynecologists (ACOG) and Society for Maternal-Fetal Medicine (SMFM) screening recommendations. ACOG’s clinical expert series recommends targeted screening for vasa previa using transvaginal ultrasonography and color Doppler as part of the midpregnancy obstetric ultrasound examination of pregnancies with risk factors.
Umbilical cord cysts
Umbilical cord cysts are sacs of fluid found in the umbilical cord. They’re most likely to develop in the first trimester and can be detected with a high-frequency ultrasound. There are generally two types of cysts— true cysts (which contain fluid from the embryo and usually go away on their own) and pseudocysts (which contain fluid from inside the umbilical cord and can be linked to certain genetic conditions). The only way to know the differences between these two types, however, is examination in a pathology lab. Prenatal diagnosis is based on observation of a round, thin-walled anechoic structure in the amniotic cavity in close approximation to the umbilical cord and separate from the fetus. Management depends on the type, size, and location of the cyst; gestational age at detection, associated anomalies, and potential for complications. Expectant management is appropriate since most cysts resolve and are not predictive of adverse pregnancy outcome. If the cysts are large, they can be associated with fetal complications such as poor growth or non–reassuring fetal heart tracings in labor. Your maternal fetal medicine specialist may recommend some tests to check for genetic and birth defects in some rare cases.
Umbilical Cord Conditions That Are Diagnosed in the Intrapartum and Postnatal Period
Umbilical cord knots
Prenatal identification of a true knot is rare and challenging. True knots occur in less than one percent of births and are generally single and loose. They are generally diagnosed postnatally and have been associated with more fetal heart tracing abnormalities during labor. Stillbirths have been associated with a higher incidence of true umbilical cord knots, but they have not been established as causal. At this time, prenatal ultrasound does not screen for this condition as it’s unclear what the best management course should be.
Umbilical cord prolapse
Umbilical cord prolapse is a condition where the umbilical cord enters the vaginal canal before your baby during labor. This can become serious if the cord becomes pinched and blocks off oxygen to your baby. Although it’s rare, you can be at risk of umbilical cord prolapse if your baby is premature or underweight, if your baby is in breech position, or if the umbilical cord is too long. If umbilical cord prolapse is detected and your baby isn’t born right away, it can cause stillbirth. In many cases, you may need to have a c-section instead of delivering vaginally.
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Managing umbilical cord conditions can require some expert help from your maternal fetal medicine specialist. To meet with our award-winning team and learn more about the right options for you and your baby, we invite you to contact our New York City office by calling or filling out our online form.
Ref : Ebbing C, Kiserud T, Johnsen SL, Albrechtsen S, Rasmussen S . Third stage of labor risks in velamentous and marginal cord insertion: a population-based study. Acta Obstet Gynecol Scand. 2015 Aug;94(8):878-83. Epub 2015 May 25
Klahr R, Fox NS, Zafman K, Hill MB, Conolly CT, Rebarber A. Frequency of spontaneous resolution of vasa previa with advancing gestational age. AJOG 221 (6) pg 646 E1-E7, Dec 2019