Influence of nuchal cord on ductus venosus assessment at 11 to 13 + 6 weeks' gestation.

OBJECTIVES: To assess the influence of the presence of nuchal cord (NC) on the evaluation of the fetal ductus venosus flow velocity waveform (DV-FVW). METHODS: This prospective study included 1174 normal non-selected singleton pregnancies between 11 and 13 + 6 weeks' gestation. We recorded the presence or absence of NC around the fetal neck, and assessed its relationship with the qualitative assessment and quantitative measurement of the DV-FVW. RESULTS: We observed NC around the fetal neck in 6.73% of cases and detected reversed flow of the a-wave of the DV-FVW in 2.98% of cases. In the group without NC, 21 of 1095 had reversed flow in the DV-FVW (1.9%; 95% CI, 1.28-3.02), whereas in the group with NC, 14 of 79 had reversed flow in the DV-FVW (17.7%; 95% CI, 16.67-40.35). We found a lower pulsatility index in fetuses without NC in comparison to those with NC (P < 0.001). We also found an association between the presence of NC and an increased occurrence of absent and reversed a-wave of the flow velocity waveforms (P < 0.001). On multivariate logistic regression analysis, a much higher occurrence of reversed DV-FVW a-wave was detected in fetuses with NC and smaller crown-rump length, and a much higher occurrence of absent DV-FVW a-wave was found in fetuses with NC and a higher maternal body mass index. CONCLUSIONS: The presence of NC modifies the sonographic findings in the qualitative and quantitative evaluation of the DV-FVW.

Cord entanglement and perinatal outcome in monoamniotic twin pregnancies.

OBJECTIVES: To assess the prevalence of cord entanglement and perinatal outcome in a large series of monoamniotic twin pregnancies and to review the recent literature on similar published large series. METHODS: Prospective observational study of all prenatally detected cases of monoamniotic twin pregnancies during an 8-year period in a tertiary fetal medicine unit. A Medline database review for publications since 2000 containing five or more cases of monoamniotic pregnancies that showed data on cord entanglement and perinatal outcome was also undertaken. RESULTS: A total of 32 monoamniotic pregnancies were diagnosed during the study period, including three conjoined twins, seven pregnancies with twin reversed arterial perfusion (TRAP) syndrome, three surgical pregnancy interruptions for discordant fetal abnormality and one miscarriage before 16 weeks' gestation. The remaining 18 monoamniotic pregnancies were included in the study analysis. All monoamniotic pregnancies were complicated with antenatal cord entanglement diagnosed by B-mode and color Doppler ultrasound. There were 34 live births and a double intrauterine death diagnosed at 19 + 2 weeks' gestation. There were two late neonatal deaths, one from congenital complete heart block and the other after surgery for transposition of the great arteries. The overall perinatal loss rate was 11.1% after 16 weeks and 5.9% after 20 weeks' gestation. The cumulative rates of cord entanglement and perinatal mortality in the reviewed literature were 74% and 21%, respectively. CONCLUSIONS: Umbilical cord entanglement is present in all monoamniotic twins when it is systematically evaluated by ultrasound and color Doppler. Perinatal mortality in monoamniotic twins is mainly a consequence of conjoined twins, TRAP, discordant anomaly and spontaneous miscarriage before 20 weeks' gestation. Expectantly managed monoamniotic twins after 20 weeks have a very good prognosis despite the finding of cord entanglement. The practice of elective very preterm delivery or other interventions to prevent cord accidents in monoamniotic twins should be re-evaluated.

Impact of nuchal cord on measurement of fetal nuchal translucency thickness.

OBJECTIVE: To define the impact of nuchal cord on the measurement of fetal nuchal translucency thickness (NT). METHODS: Between December 2004 and June 2006, we examined prospectively 53 fetuses that were observed on routine first-trimester ultrasound examination between 11 + 3 and 13 + 6 weeks of gestation to have nuchal cord causing an indentation in the skin in the nuchal region. The fetuses were re-examined after a median interval of 132 min, when the cord was no longer around the neck and indentation of the skin had resolved. Various NT measurements (highest, lowest, mean) with the cord located around the neck (nuchal cord) were compared with NT measurements in the absence of nuchal cord ('true' NT) in the same fetuses. Measurements were considered to be equal when they were within mean +/- 1.96 SD, defined by our own intraobserver repeatability according to the method of Bland and Altman. RESULTS: The mean of the largest and the smallest of six measurements in the presence of nuchal cord fell within the mean +/- 1.96 SD of our own intraobserver repeatability, i.e. gave a correct estimate of the true NT, in 80% of fetuses, while the NT was overestimated in 10% and underestimated in 10% of fetuses. The largest and the smallest of six measurements in the presence of nuchal cord gave an underestimate of the true NT in 2% of fetuses and an overestimate in 4% of fetuses, respectively. CONCLUSION: There is a wide scattering of measurements in fetuses with nuchal cord in comparison to the same fetuses in the absence of nuchal cord. This prevents accurate prediction of the true NT, although the largest and smallest of repeat measurements with nuchal cord can allow calculation of the highest and lowest possible risks, respectively. These facts must be taken into consideration in counseling patients.