Velamentous insertion of the cord in the first trimester

Current Perspectives of Prenatal Sonography of Umbilical Cord Morphology

The umbilical cord constitutes a continuation of the fetal cardiovascular system anatomically bridging between the placenta and the fetus. This structure, critical in human development, enables mobility of the developing fetus within the gestational sac in contrast to the placenta, which is anchored to the uterine wall. The umbilical cord is protected by unique, robust anatomical features, which include: length of the umbilical cord, Wharton’s jelly, two umbilical arteries, coiling, and suspension in amniotic fluid. These features all contribute to protect and buffer this essential structure from potential detrimental twisting, shearing, torsion, and compression forces throughout gestation, and specifically during labor and delivery. The arterial components of the umbilical cord are further protected by the presence of Hyrtl’s anastomosis between the two respective umbilical arteries. Abnormalities of the umbilical cord are uncommon yet include excessively long or short cords, hyper or hypocoiling, cysts, single umbilical artery, supernumerary vessels, rarely an absent umbilical cord, stricture, furcate and velamentous insertions (including vasa previa), umbilical vein and arterial thrombosis, umbilical artery aneurysm, hematomas, and tumors (including hemangioma angiomyxoma and teratoma). This commentary will address current perspectives of prenatal sonography of the umbilical cord, including structural anomalies and the potential impact of future imaging technologies.

Velamentous cord insertion in a singleton pregnancy: an obscure cause of emergency cesarean-a case report

Approximately 2% of low-risk pregnant women still require an emergency Cesarean section after the onset of labor. Because it is likely that half of these cases are associated with placental and umbilical cord abnormalities, it is thought that prenatal detection of such abnormalities would reduce the number of emergency cesarean sections in low-risk women. Velamentous cord insertion is an abnormal cord insertion in which the umbilical vessels diverge as they traverse between the amnion and chorion before reaching the placenta. With a reported incidence of 1% in singleton pregnancies, it has been associated with several obstetric complications. This condition has been diagnosed by ultrasonography with a sensitivity of 67% and specificity of 100% in the second trimester. The present case highlights the importance of the systematic assessment of the placental cord insertion site at routine obstetric ultrasound and the potential of identifying pregnancies with velamentous insertion and, therefore, those at risk for obstetric complications.

Umbilical cord insertion site in early gestation and development of placenta

AIM

To study the relation of umbilical cord insertion (CI) site in early gestation and placental development from the chorion villosum.

METHODS

We ultrasonically measured the distance between the internal cervical Os and the CI site (CID), the distance between the internal cervical Os and lower placenta edge (PLD), and placental thickness at early (10-12 weeks) and mid-gestation (18-20 weeks).

RESULTS

CID in early gestation (CID-Early) correlated with CID in mid-gestation (r(2)=0.171; P<0.01). CID-Early correlated with PLD in mid-gestation (r(2)=0.093; P<0.01). Thickness of chorion villosum or placenta in early gestation did not correlate with that at mid-gestation. Increasing thickness of placenta was significantly higher in long CID-Early (> or =20 mm) cases than short cases (<20 mm) (P<0.05).

CONCLUSIONS

The process of placental development and the placental location are affected by CI location at early gestation, and suggests that this process might be affected by poor blood supply from the low uterine segment when CI site is close to the internal cervical Os.

Cord insertion into the lower third of the uterus in the first trimester is associated with placental and umbilical cord abnormalities

OBJECTIVES

To assess the feasibility of detecting the cord insertion site during the late first trimester, and to investigate the possible association between perinatal complications and a cord insertion in the lower third of the uterus in the first trimester.

METHODS

This was a prospective cohort study in which the positional relationship between the uterus and the cord insertion site was examined using gray-scale transvaginal sonography at 9-11 weeks of gestation. The distance between the internal os and the fundus was divided equally into three parts. Cord insertions located in the upper or middle thirds were defined as normal (controls), and those located in the lower third were defined as cases, regardless of their relationship to the chorion villosum. Third-trimester sonography and pathological examination of the placenta and cord at delivery were performed to check for placental/cord abnormalities. The univariate association between the location of the cord insertion in the first trimester and placental and umbilical cord abnormalities and perinatal complications was assessed.

RESULTS

The cord insertion site was identified in 318/340 (93.5%) cases at 9-11 weeks of gestation and it was in the lower third of the uterus in 35 (11.0%) cases. Of these 35, the cord insertion was found at delivery to be low in nine cases (26%) and the placenta was low-lying at delivery in eight (23%). None of the 283 cases with a normal cord insertion in the first trimester was found to have a low-lying placenta at delivery (P < 0.0001). Ten (29%) of the cases with a low cord insertion and four (1.4%) with a normal cord insertion in the first trimester had a velamentous or marginal cord insertion at delivery (P < 0.0001). At delivery, five (14%) of the low cord insertion cases and four (1.4%) of the normal cord insertion cases (P < 0.0001) had some form of placental malformation, including accessory placenta and infarction of the placenta. An emergency Cesarean section was performed in four (11%) and six (2.1%) of the low and normal cord insertion cases, respectively (P = 0.003).

CONCLUSION

Developmental abnormalities of the placenta and umbilical cord occur frequently in cases in which the cord insertion is in the lower third of the uterus in the first trimester. We suggest that screening for the cord insertion site at 9-11 weeks of gestation may have clinical significance for predicting abnormalities of the cord and the placenta at delivery.

Velamentous insertion of the umbilical cord: a first-trimester sonographic screening study

OBJECTIVE

The purpose of this study was to determine the feasibility of prenatal sonography for detecting velamentous insertion of the umbilical cord in singleton pregnancies at the 11- to 14-week scan.

METHODS

The placental umbilical cord insertion site was prospectively examined at the time of the routine first-trimester scan between 11 and 14 weeks as part of ongoing first-trimester sonographic screening for chromosomal abnormalities.

RESULTS

Over a 1-year period, 533 consecutive singleton pregnancies were examined by a fetal medicine specialist at a median gestational age of 12 weeks. In 5 cases, a velamentous umbilical cord insertion was diagnosed, with a prevalence rate of 1 (0.9%) per 107. The diagnosis was further confirmed at the second-trimester scan and at the time of delivery in all cases.

CONCLUSIONS

The placental umbilical cord insertion site can be readily determined by sonography at the time of the 11- to 14-week scan. Sonographic examination at this early gestational age provides the opportunity for screening for velamentous insertion of the umbilical cord in the first trimester, allowing close surveillance of the pregnancy for potential complications associated with this condition.

Early detection of fetal structural abnormalities

Most published data on the detection of fetal anomalies at 11-14 weeks are from specialized centres with considerable experience in fetal anomaly scanning. However, there is still limited information on the feasibility and limitations of the screening of these anomalies compared with the now classical mid-gestation screening. This review indicates that overall, the detection rate of fetal anomalies at 11-14 weeks is 44% compared with 74% by the mid-pregnancy scan. Major abnormalities of the fetal head, abdominal wall and urinary tract, and of the umbilical cord and placenta, can be reliably detected at 10-11 weeks of gestation. Detection of other anomalies such as spina bifida, diaphragmatic hernia or heart defects is limited before 13 weeks of gestation. So far it cannot be stated that routine first trimester screening can be used on a large scale to evaluate the fetal spine and heart in the general population. In particular, in screening for congenital heart defects, the ability to perform a full cardiac examination increases from 20% at 11 weeks to 92% at 13 weeks. The early prenatal diagnosis of these anomalies may be improved by screening at 13-14 weeks rather than during the first trimester.

Sonographic prenatal diagnosis of marginal placental cord insertion: clinical importance

OBJECTIVE

To assess the impact of a sonographic diagnosis of marginal placental cord insertion on birth weight and duration of pregnancy.

METHODS

A retrospective chart review was performed for 100 singleton pregnancies with prospectively identified marginal placental cord insertion.

RESULTS

Birth weights below the 10th percentile occurred in 6.25% of pregnancies without preeclampsia. Spontaneous preterm delivery occurred in 7.3% of pregnancies without preeclampsia. Rates of birth weight below the 10th percentile and preterm delivery were not significantly different from those in the general population. Preeclampsia developed in 4 patients; all had elective preterm deliveries, and all gave birth to neonates with birth weights below the 10th percentile.

CONCLUSIONS

A prenatal diagnosis of marginal placental cord insertion is not associated with increased risk of growth impairment or preterm delivery.