Velamentous cord insertion

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Velamentous cord insertion
Other namesVelamentous Placenta
Velamentous Cord insertion.png
Normal umbilical cord insertion and velamentous umbilical cord insertion in pregnancy, with and without vasa previa.
Specialty Obstetrics   OOjs UI icon edit-ltr-progressive.svg
Symptoms Blood vessel compression, [1] [2] decrease in blood supply to the fetus, [2] [3] impaired growth and development of the fetus. [4] [5]
Risk factors Multiple gestation, [1] [2] [6] [7] [8] placental anomalies [9] previous pregnancy with abnormal cord insertion [2]
Diagnostic method Abdominal ultrasound [3] [4]
Treatment Caesarean section [7]
Frequency0.1%-1.8% of pregnancies [6]

Velamentous cord insertion is a complication of pregnancy where the umbilical cord is inserted in the fetal membranes. It is a major cause of antepartum hemorrhage that leads to loss of fetal blood and associated with high perinatal mortality. In normal pregnancies, the umbilical cord inserts into the middle of the placental mass and is completely encased by the amniotic sac. The vessels are hence normally protected by Wharton's jelly, which prevents rupture during pregnancy and labor. [10] In velamentous cord insertion, the vessels of the umbilical cord are improperly inserted in the chorioamniotic membrane, and hence the vessels traverse between the amnion and the chorion towards the placenta. [1] [11] Without Wharton's jelly protecting the vessels, the exposed vessels are susceptible to compression and rupture. [1] [9]

Contents

The exact cause of velamentous cord insertion is unknown, although risk factors include nulliparity, [2] [6] the use of assisted reproductive technology, [6] [12] maternal obesity, [6] [7] and pregnancy with other placental anomalies. [9] Velamentous cord insertion is often diagnosed using an abdominal ultrasound. [3] [4] This is most successful in the second trimester, [13] however Color Doppler ultrasound [14] or transvaginal ultrasound [15] can be used in difficult cases, such as when the placenta is located posteriorly. If the woman is diagnosed with velamentous cord insertion, the pregnancy is closely monitored, especially as velamentous cord insertion is a strong risk factor for vasa previa, where the exposed vessels cross the cervix and are at high risk of rupture during membrane rupture in early labor. [9] Management strategies for velamentous cord insertion also involve determining the presence of vasa previa. [16] Velamentous cord insertion impacts fetal development during pregnancy by impairing the development of the placenta [2] and modifying the efficiency of placental function. [17] This can manifest in a range of adverse perinatal outcomes, such as fetal growth restriction, [4] [5] placental abruption, [3] [6] [16] [18] abnormal fetal heart rate patterns, [3] [10] [19] and fetal death. [6] [7] [9] Velamentous cord insertion affects between 0.1%-1.8% of pregnancies, [6] though its incidence increases ten-fold in multiple pregnancies. [1] [10]

Signs and symptoms

Signs and symptoms of velamentous cord insertion during pregnancy include blood vessel compression, [1] [2] decrease in blood supply to the fetus, [2] [3] and impaired growth and development of the fetus. [4] [5] Blood tests taken in the second trimester may reveal increased levels of serum human chorionic gonadotropin and reduced levels of alpha-fetoprotein. [20] [21] The mother may also experience vaginal bleeding, particularly in the third trimester. [11] Women with velamentous cord insertion may not experience any symptoms throughout pregnancy. [16] During delivery, there may be slow or abnormal fetal heart rate patterns [3] [10] [19] and there may be excessive bleeding or hemorrhage, particularly if the fetal vessels rupture. [1] [7] [9] [22]

Pathophysiology

The exact mechanisms leading to insertion of the umbilical cord in the fetal membranes are unknown, although they are likely to occur in the first trimester. [23] One theory is that velamentous cord insertion may arise from the process of placental trophotropism, which is the phenomenon where the placenta migrates towards areas which have better blood flow with advancing gestation. The placenta grows in regions with better blood supply and portions atrophy in regions of poor blood flow. This process of atrophy may result in the exposure of umbilical blood vessels, causing marginal or peripheral placental insertion to evolve to velamentous insertion over time. [1] [10] [23]

Placentas with velamentous cord insertion have a lower vessel density. [2] As the growth of the fetus is dependent on the organization, mass, and nutrient-transfer capacity of the placenta, fetal development is hence hindered in velamentous cord insertion. This can lead to fetal malformations [2] [24] and low birth weight. [2] [6] [10] The umbilical vessels may also be longer compared to normal, [2] particularly when the site of velamentous cord insertion is in the lower uterine section as the extension of the uterine isthmus as pregnancy advances causes vessel elongation. [3] This results in increased vascular resistance, which impedes nutrient transfer to the fetus. [2]

The umbilical vessels experience increased pressure and compression as they are not protected by Wharton's jelly. This can cause decreased or acute cessation of blood flow, decreased cardiac output, and pulmonary complications in the newborn. [2] The elongated, exposed vessels in lower velamentous cord insertion cases are more readily compressed by the fetus, hence there is an even greater risk of non-reassuring fetal heart rate pattern and emergency caesarean section. [2] [3]

The growth-restricting impacts of placental insufficiency resulting from velamentous cord insertion can also augment the effects of increased pressure to the umbilical vessels. [2] Normally in the second half of pregnancy, one-third of fetal cardiac output is directed towards the placenta. This fraction is reduced to around one-fifth in the last few weeks of pregnancy, while the remaining umbilical blood is recirculated in the fetal body, corresponding with decreased fetal reserves of oxygen. [25] In pregnancies with growth restriction, the fraction of fetal cardiac output distributed to the placenta decreases, further lowering fetal reserves. [2] [25] This can result in increased risk of caesarean delivery, fetal hypoxia, and perinatal death in pregnancies with velamentous cord insertion. [2]

Damage to the umbilical cord vessels can occur when the amniotic membranes are ruptured, particularly in the case of vasa previa, potentially leading to fetal exsanguination. [3] [8] [26] If the umbilical vessels are positioned such that their rupture is likely during labor, an elective operative birth at 35–36 weeks gestation may be planned, and corticosteroids may be administered in order to assist with fetal lung maturation. [7] [9] Overall, velamentous cord insertion doubles the risk of both preterm birth and acute caesarean section. [2]

Risk factors

The following have been identified as risk factors for velamentous cord insertion:


Diagnosis

Abdominal ultrasound can be used to visualize the insertion site of the umbilical cord. [3] [4] Overall, visualization is most successful in the second trimester, [13] however routine ultrasound examination in the second trimester may not detect velamentous cord insertion if the condition develops after the remodelling of the placenta as gestation advances. [10] Visualization becomes increasingly difficult in the third trimester as the fetus may obscure the insertion site. [4] [13]

The umbilical cord and its insertion site may be obscured by the fetus, such as in posterior placenta or in low-lying placenta, or may be difficult to visualise due to conditions such as maternal obesity. [10] [15] In these cases, the use of Color Doppler ultrasound or transvaginal ultrasound can enhance the visualization of the umbilical cord, and are able to diagnose velamentous cord insertion at 18–20 weeks. [14] [15]

Management

If velamentous cord insertion is diagnosed, fetal growth is assessed every four weeks using ultrasound beginning at 28 weeks. If intrauterine growth restriction is observed, the umbilical cord is also assessed for signs of compression. Non-stress tests may be performed twice a week to ensure adequate blood flow to the fetus. [16] The amniotic fluid may be frequently assessed for high levels of inflammatory markers such as interleukin-6 which can indicate intra-amniotic inflammation. [28] [29]

Upon diagnosis of velamentous cord insertion, transvaginal ultrasound with Color Doppler may also be performed to determine whether any of the exposed vessels are within two centimeters (or five centimeters, a more common threshold recently) of the internal cervical os. If such vessels are identified, vasa previa may be present and cervical length is measured every week to determine the risk of premature rupture of membranes. [16]

Women diagnosed with velamentous cord insertion may also receive counselling about the condition, its risks, and potential courses of action, including preterm delivery or caesarean delivery. [7]

The newborn may be delivered via normal vagina labor if there are no signs of fetal distress. [2] Fetal heart rate is continuously monitored for slow or abnormal heart rate patterns which may indicate fetal distress during labor. [7] If the exposed blood vessels are near the cervix or are at risk of rupturing, the newborn may be delivered via caesarean section as early as 35 weeks gestation. [7] [9]

Complications

Maternal

Fetal

In twins, one or both of the fetuses may have velamentous cord insertion, which can lead to birth-weight discordance, where one twin weighs significantly more at birth than the other, [2] [30] and selective fetal growth restriction. [31] These complications particularly arise in the case of monochorionic twins, where identical twins share the same placenta. [2] [32]

Epidemiology

Velamentous cord insertion occurs in between 0.1%-1.8% of all pregnancies, [6] and is eight to ten times more frequent in multiple pregnancies. [1] [3] [12] This risk is doubled in the case of monochorionic twins, and tripled in the case of fetal growth restriction. [1] It is thought that sex may be a determinant of abnormal cord insertions, however there is conflicting evidence as to whether male or female fetuses are linked to greater risk of velamentous cord insertion. [2] [6]

Related Research Articles

Obstetrics is the field of study concentrated on pregnancy, childbirth and the postpartum period. As a medical specialty, obstetrics is combined with gynecology under the discipline known as obstetrics and gynecology (OB/GYN), which is a surgical field.

<span class="mw-page-title-main">Placenta</span> Organ that connects the fetus to the uterine wall

The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ, producing hormones that regulate both maternal and fetal physiology during pregnancy. The placenta connects to the fetus via the umbilical cord, and on the opposite aspect to the maternal uterus in a species-dependent manner. In humans, a thin layer of maternal decidual (endometrial) tissue comes away with the placenta when it is expelled from the uterus following birth. Placentas are a defining characteristic of placental mammals, but are also found in marsupials and some non-mammals with varying levels of development.

<span class="mw-page-title-main">Amniocentesis</span> Sampling of amniotic fluid done mainly to detect fetal chromosomal abnormalities

Amniocentesis is a medical procedure used primarily in the prenatal diagnosis of genetic conditions. It has other uses such as in the assessment of infection and fetal lung maturity. Prenatal diagnostic testing, which includes amniocentesis, is necessary to conclusively diagnose the majority of genetic disorders, with amniocentesis being the gold-standard procedure after 15 weeks' gestation.

<span class="mw-page-title-main">Placenta praevia</span> Medical condition

Placenta praevia is when the placenta attaches inside the uterus but in a position near or over the cervical opening. Symptoms include vaginal bleeding in the second half of pregnancy. The bleeding is bright red and tends not to be associated with pain. Complications may include placenta accreta, dangerously low blood pressure, or bleeding after delivery. Complications for the baby may include fetal growth restriction.

Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. It is typically diagnosed by ultrasound when the amniotic fluid index (AFI) measures less than 5 cm or when the single deepest pocket (SDP) of amniotic fluid measures less than 2 cm. Amniotic fluid is necessary to allow for normal fetal movement, lung development, and cushioning from uterine compression. Low amniotic fluid can be attributed to a maternal, fetal, placental or idiopathic cause and can result in poor fetal outcomes including death. The prognosis of the fetus is dependent on the etiology, gestational age at diagnosis, and the severity of the oligohydramnios.

<span class="mw-page-title-main">Twin-to-twin transfusion syndrome</span> Medical condition

Twin-to-twin transfusion syndrome (TTTS), also known as feto-fetal transfusion syndrome (FFTS), twin oligohydramnios-polyhydramnios sequence (TOPS) and stuck twin syndrome, is a complication of monochorionic multiple pregnancies in which there is disproportionate blood supply between the fetuses. This leads to unequal levels of amniotic fluid between each fetus and usually leads to death of the undersupplied twin and, without treatment, usually death or a range of birth defects or disabilities for a surviving twin, such as underdeveloped, damaged or missing limbs, digits or organs, especially cerebral palsy.

<span class="mw-page-title-main">Placental abruption</span> Medical condition

Placental abruption is when the placenta separates early from the uterus, in other words separates before childbirth. It occurs most commonly around 25 weeks of pregnancy. Symptoms may include vaginal bleeding, lower abdominal pain, and dangerously low blood pressure. Complications for the mother can include disseminated intravascular coagulopathy and kidney failure. Complications for the baby can include fetal distress, low birthweight, preterm delivery, and stillbirth.

Antepartum bleeding, also known as antepartum haemorrhage (APH) or prepartum hemorrhage, is genital bleeding during pregnancy after the 28th week of pregnancy up to delivery.

Obstetrical bleeding is bleeding in pregnancy that occurs before, during, or after childbirth. Bleeding before childbirth is that which occurs after 24 weeks of pregnancy. Bleeding may be vaginal or less commonly into the abdominal cavity. Bleeding which occurs before 24 weeks is known as early pregnancy bleeding.

<span class="mw-page-title-main">Prelabor rupture of membranes</span> Medical condition

Prelabor rupture of membranes (PROM), previously known as premature rupture of membranes, is breakage of the amniotic sac before the onset of labor. Women usually experience a painless gush or a steady leakage of fluid from the vagina. Complications in the baby may include premature birth, cord compression, and infection. Complications in the mother may include placental abruption and postpartum endometritis.

<span class="mw-page-title-main">Complications of pregnancy</span> Medical condition

Complications of pregnancy are health problems that are related to, or arise during pregnancy. Complications that occur primarily during childbirth are termed obstetric labor complications, and problems that occur primarily after childbirth are termed puerperal disorders. While some complications improve or are fully resolved after pregnancy, some may lead to lasting effects, morbidity, or in the most severe cases, maternal or fetal mortality.

<span class="mw-page-title-main">Placenta accreta spectrum</span> Medical condition

Placenta accreta occurs when all or part of the placenta attaches abnormally to the myometrium. Three grades of abnormal placental attachment are defined according to the depth of attachment and invasion into the muscular layers of the uterus:

  1. Accreta – chorionic villi attached to the myometrium, rather than being restricted within the decidua basalis.
  2. Increta – chorionic villi invaded into the myometrium.
  3. Percreta – chorionic villi invaded through the perimetrium.
<span class="mw-page-title-main">Vasa praevia</span> Condition in which fetal blood vessels cross or run near the internal opening of the uterus.

Vasa praevia is a condition in which fetal blood vessels cross or run near the internal opening of the uterus. These vessels are at risk of rupture when the supporting membranes rupture, as they are unsupported by the umbilical cord or placental tissue.

Placental insufficiency or utero-placental insufficiency is the failure of the placenta to deliver sufficient nutrients to the fetus during pregnancy, and is often a result of insufficient blood flow to the placenta. The term is also sometimes used to designate late decelerations of fetal heart rate as measured by cardiotocography or an NST, even if there is no other evidence of reduced blood flow to the placenta, normal uterine blood flow rate being 600mL/min.

<span class="mw-page-title-main">Percutaneous umbilical cord blood sampling</span>

Percutaneous umbilical cord blood sampling (PUBS), also called cordocentesis, fetal blood sampling, or umbilical vein sampling is a diagnostic genetic test that examines blood from the fetal umbilical cord to detect fetal abnormalities. Fetal and maternal blood supply are typically connected in utero with one vein and two arteries to the fetus. The umbilical vein is responsible for delivering oxygen rich blood to the fetus from the mother; the umbilical arteries are responsible for removing oxygen poor blood from the fetus. This allows for the fetus’ tissues to properly perfuse. PUBS provides a means of rapid chromosome analysis and is useful when information cannot be obtained through amniocentesis, chorionic villus sampling, or ultrasound ; this test carries a significant risk of complication and is typically reserved for pregnancies determined to be at high risk for genetic defect. It has been used with mothers with immune thrombocytopenic purpura.

<span class="mw-page-title-main">Placental disease</span> Medical condition

A placental disease is any disease, disorder, or pathology of the placenta.

<span class="mw-page-title-main">Circumvallate placenta</span> Medical condition

Circumvallate placenta is a rare condition affecting about 1-2% of pregnancies, in which the amnion and chorion fetal membranes essentially "double back" on the fetal side around the edges of the placenta. After delivery, a circumvallate placenta has a thick ring of membranes on its fetal surface. Circumvallate placenta is a placental morphological abnormality associated with increased fetal morbidity and mortality due to the restricted availability of nutrients and oxygen to the developing fetus.

Amnioinfusion is a method in which isotonic fluid is instilled into the uterine cavity.

Early pregnancy bleeding refers to vaginal bleeding before 14 weeks of gestational age. If the bleeding is significant, hemorrhagic shock may occur. Concern for shock is increased in those who have loss of consciousness, chest pain, shortness of breath, or shoulder pain.

The anomaly scan, also sometimes called the anatomy scan, 20-week ultrasound, or level 2 ultrasound, evaluates anatomic structures of the fetus, placenta, and maternal pelvic organs. This scan is an important and common component of routine prenatal care. The function of the ultrasound is to measure the fetus so that growth abnormalities can be recognized quickly later in pregnancy, to assess for congenital malformations and multiple pregnancies, and to plan method of delivery.

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  30. ↑ Kent E, Breathnach F, Gillan J, McAuliffe F, Geary M, Daly S, Higgins J, Dornan J, Morrison J, Burke G, Higgins S, Carroll S, Dicker P, Manning F, Malone F (2011). "Placental cord insertion and birthweight discordance in twin pregnancies: results of the national prospective EsPRIT trial". American Journal of Obstetrics and Gynecology. 204 (1): S20. doi:10.1016/j.ajog.2010.10.044.
  31. ↑ Kalafat E, Thilaganathan B, Papageorghiou A, Bhide A, Khalil A (2018). "Significance of placental cord insertion site in twin pregnancys". Ultrasound in Obstetrics & Gynecology. 52 (3): 378–384. doi: 10.1002/uog.18914 . PMID   28976606. S2CID   10906198.
  32. ↑ Sato Y (2006). "Increased Prevalence of Fetal Thrombi in Monochorionic-Twin Placentas. Pediatrics". Pediatrics. 117 (1): e113–e117. doi:10.1542/peds.2005-1501. PMID   16361224. S2CID   19061448.
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