Abnormal ductus venosus blood flow: a clue to umbilical cord complication

Is nuchal cord justified as a cause of obstetrician anxiety?

PURPOSE

Birth asphyxia leading to acidosis comprises 20-60 % of perinatal mortality. Nuchal cord (NC) is one of the possible causes of birth asphyxia. Majority of fetuses who are antenatally detected to have nuchal cord are able to achieve successful vaginal birth. The purpose of this study was to analyze the effect of nuchal cord on fetal acid base status and perinatal outcome in vaginal deliveries.

STUDY DESIGN

150 parturients were equally divided into three groups after vaginal delivery based on no NC, single and multiple loops. Umbilical cord arterial blood was analyzed for biochemical markers i.e. pH, PO2, SPO2, PCO2, HCO3 (-), standard base excess and lactate for acidosis. Labor complications like abnormal FHR, meconium-stained liquor, prolonged second stage, instrumental vaginal delivery, third stage complications were compared. In neonates, birth weight, Apgar score ≤7 at 5 min, NICU admission and other morbidity and mortality during hospital stay were compared among groups using suitable statistical tests. Above parameters were also compared between tight and loose loops.

RESULT

Nuchal cord groups had significantly higher frequency of labor complications than no NC group, especially tight loops. Neonates with NC had significantly higher frequency of meconium-stained liquor, Apgar score ≤7 at 5 min, deranged biochemical markers, NICU transfer. However, none of the neonate had pH in acidosis range and majority were discharged in healthy condition.

CONCLUSION

Patients with NC are likely to have uneventful labor and delivery as cord compression is transient and most fetuses are able to compensate for reduce umbilical blood flow. Routine antenatal ultrasound scan is not advisable, as mode of delivery and labor management does not change with detection of NC antenatally. Therefore, vaginal delivery with routine labor protocol can be allowed in cases of nuchal cord.

Ultrasound detection of nuchal cord prior to labor induction and the risk of Cesarean section

OBJECTIVES

To investigate the ability of ultrasound to detect the presence of a nuchal cord immediately prior to induction of labor and the association of its presence with delivery by Cesarean section.

METHODS

A transabdominal ultrasound scan using gray-scale and color Doppler imaging was performed immediately prior to induction of labor in 289 women in a prospective study to assess the presence of a nuchal cord. The presence of a nuchal cord was classified as present, absent or uncertain. The outcomes of labor, delivery and the neonates were obtained from the patient notes after delivery.

RESULTS

A nuchal cord was present at 18% of deliveries. The incidence was not affected by parity, fetal position or reduced amniotic fluid volume. The sensitivity of ultrasound in diagnosing a nuchal cord was 37.5%, with specificity, positive and negative predictive values of 80%, 29% and 85%, respectively. The presence of a nuchal cord did not significantly increase the risk of delivery by Cesarean section (35% vs. 28%; relative risk = 1.22; 95% CI, 0.80-1.87), instrumental delivery for fetal distress, an abnormal cardiotocograph in labor or at delivery, an Apgar score < 7 at 1 min, arterial cord pH < 7.1 or neonatal unit admission.

CONCLUSIONS

The sensitivity of the ultrasound diagnosis of a nuchal cord is low prior to induction of labor at term. A nuchal cord does not appear to increase the risk of Cesarean section or of poor neonatal outcome. The low ultrasound detection rate of a nuchal cord limits its use in decision making prior to induction of labor in high-risk pregnancies.

Ductus venosus blood flow velocity characteristics of fetuses with single umbilical artery

OBJECTIVES

Sonographic Doppler evaluation of the fetal ductus venosus has been proved to be useful in the evaluation of fetal cardiac function. The aim of this study was to investigate the ductus venosus blood flow profile in fetuses with single umbilical artery and to correlate it with the umbilical cord morphology.

METHODS

Fetuses at >20 weeks' gestation with single umbilical artery who were otherwise healthy were consecutively enrolled into the study. The sonographic examination included evaluation of the following Doppler parameters: umbilical artery resistance index, maximum blood flow velocity of the ductus venosus during ventricular systole (S-peak) and atrial contraction (A-wave), ductus venosus time-averaged maximum velocity (TAMXV), and pulsatility index for veins (PIV). The cross-sectional area of the umbilical cord and its vessels were measured in all cases. The Doppler and morphometric values obtained were plotted on reference ranges.

RESULTS

A total of 88 fetuses with single umbilical artery were scanned during the study period. Of these 52 met the inclusion criteria. The S-peak velocity, A-wave velocity, and TAMXV were below the 5th centile for gestational age in 57.7%, 59.6%, and 57.7% of cases, respectively. The PIV was within the normal range in 80.1% of cases. The umbilical vein cross-sectional area of fetuses with single umbilical artery was above the 95th centile for gestational age in 34.6% cases.

CONCLUSIONS

The ductus venosus blood flow pattern is different in fetuses with single umbilical artery from that in those with a three-vessel cord. This difference may be caused in part by the particular morphology of umbilical cords with a single artery.

Intrauterine growth restriction (IUGR): biometric and Doppler assessment

Intrauterine growth restriction (IUGR) is a common complication in pregnancy and influences morbidity and mortality at all stages of life. Historically, the management of IUGR has been dependent on antenatal biophysical testing and umbilical artery Doppler studies. With recent Doppler studies of the fetal central circulation, including intracardiac flows and the ductus venosus, better timing of delivery to minimize morbidity may be possible. This review will provide the reader with tools to diagnose IUGR, more accurately date the IUGR pregnancy with poor dating criteria, and better assess the condition of the IUGR fetus. A brief review of animal models of IUGR is presented to demonstrate research directions for answering human clinical questions and potentially carrying therapeutic intervention from the bench to the bedside.