R. M. Lewinsky

Sonographic estimation of umbilical coiling index and correlation with doppler flow characteristics

Objective To quantitate umbilical vascular coiling antenatally, and to correlate the coiling index with Doppler flow characteristics in umbilical vessels. Methods We studied 45 normal term fetuses within 24 hours before delivery. The umbilical coiling index was calculated using sonographic longitudinal views of cord vessels from several segments antenatally, and by dividing the total number of helices by the cord length (in centimeters) postnatally. Doppler flow velocities were obtained from umbilical arteries and vein in each cord. Flow characteristics were correlated with the umbilical coiling index. Results The mean (± standard deviation) umbilical coiling index was 0.44 ± 0.11 in the antepartum period and 0.28 ± 0.08 after birth. Regression analysis showed a significant linear trend (r = 0.71, P < .001). The correlations between sonographic coiling index and umbilical arterial Doppler flow characteristics (mean velocity, pulsatility index, resistance index, and systolic-diastolic ratio) were not significant. The sonographic coiling index was related to time-averaged velocity and flow in the umbilical vein. A good correlation was found between umbilical vein flow and the coiling index, with a significant linear trend (r = 0.59, P < .001). Conclusions An intrauterine umbilical coiling index can be determined by ultrasound and correlates well with the actual index at birth. The sonographic umbilical coiling index is related to Doppler flow characteristics in the umbilical vein.

Autonomic Imbalance in Preeclampsia: Evidence for Increased Sympathetic Tone in Response to the Supine-Pressor Test

Objective To examine whether an increase in sympathetic nervous tone contributes to the augmented response to cardiovascular reflex testing in preeclamptic women. Methods Maternal electrocardiograms were recorded from 11 nonpregnant women and 25 normotensive and 15 preeclamptic nulliparous women at term, during periods of quiet respiration in the left-lateral position and after shifting to the supine position. Power spectral analysis was applied to epochs of 512 consecutive beat-to-beat intervals to determine the contribution of sympathetic tone, parasympathetic tone, and respiratory sinus arrhythmia to heart rate variability. Results Both normotensive and preeclamptic pregnant women showed a significant decrease in respiratory sinus arrhythmia and an increase in sympathetic tone compared with nonpregnant women. In nonpregnant and in normotensive pregnant women, shifting from the left-lateral to the supine position did not cause any change in autonomic characteristics. In contrast, preeclamptic women demonstrated a marked increase in power within the very lowfrequency range representing sympathetic tone, from 288 ± 214 to 556 ± 322 second2/Hz, in response to the same challenge (P < .05). Conclusion Third-trimester pregnancy is characterized by sympathetic overactivity. When complicated by preeclampsia, sympathetic overreactivity to cardiovascular reflex testing is observed. Our data support the notion that the pathophysiologic phenomena that characterize preeclampsia are mediated not only by circulating or locally acting vasoactive substances, but also, at least in part, by an increase in sympathetic nervous tone.

Transient Ascites Associated with a Fetal Ovarian Cyst

A case of fetal ovarian cyst associated with transient ascites is presented. The cyst showed serial changes from a fluid-debris interface to an anechoic structure. The changing ultrasonographic appearance of the cyst, disappearance of ascites and postnatal spontaneous resolution, suggests in utero torsion of the cyst.

Maternal Echocardiography in Hypertensive Pregnancies

Echocardiographic hemodynamic and left ventricular parameters were determined in 14 normotensive and 18 hypertensive women during the last trimester of pregnancy. The hypertensive patients had significantly higher mean values of total peripheral resistance (p less than 0.001), maximum velocity of posterior wall motion (p less than 0.05), mean velocity of circumferential fiber shortening (p less than 0.01) and percent fiber shortening of left ventricular diameter (p less than 0.05). The mean values for heart rate, stroke volume, cardiac output, cardiac index, left ventricular posterior wall thickness and septal thickness did not differ significantly in both groups. These results reflect increased cardiac contractility related to elevated peripheral vascular resistance in subjects with pregnancy-induced hypertension.

Fetal internal carotid artery flow velocity time waveforms in twin pregnancies

The fetal internal carotid artery and umbilical artery flow velocity time waveforms were studied in 17 consecutive twin pregnancies. The pulsatility index was calculated for each fetus in each artery as an index of vascular resistance. All studies were done within 14 days before delivery. In 8 pregnancies both fetuses were of birthweight appropriate for gestational age; whereas, in 9 patients one or both of the infants were small for gestational age (SGA). From ultrasound criteria and Doppler studies of the umbilical and fetal internal carotid arteries, decreased fetal internal carotid artery pulsatility index (cut off value less than or equal to 1.2) was found to be the best predictor of SGA (sensitivity 83%, specificity 95%, positive predictive value 91%, negative predictive value 91%).

Decrease in pulsatile flow in the internal carotid artery in fetal hydrocephalus

Summary. The effect of ventriculomegaly on pulsatile flow in the internal carotid arteries has been studied by Doppler ultrasound in four hydrocephalic fetuses. The pulsatility index showed progressive elevation proportional to the developing ventriculomegaly and thus may be a valuable index for the study of the mechanism of brain injury and for the determination of optimal timing of intervention.

Fetal and Uteroplacental Flow Velocity Waveforms in the Expectant Management of Placental Abruption

The change in flow velocity waveforms was assessed by Doppler ultrasound in the course of evolution of placental separation. The velocity changes reflected a high response to blood flow in the placental circulation along with decreased cerebral vascular resistance.

Antepartum fetal pulse oximetry

OBJECTIVE To examine the feasibility of antepartum fetal pulse oximetry by using a specially designed probe. STUDY DESIGN Twenty multiparous patients at term planned for induction of labor. The probe was passed through the cervix and held against the fetal scalp. Two laser diodes provided light in the near-infrared spectral region. Only reflected signals of both wavelengths which were consistent in pulse frequency and phase and with an AC/DC ratio of > 0.02% were considered usable. RESULTS Usable measurements were obtained in 16 out of 20 cases. Overall usable signal time was 45% (range 30.2-61.5%). There was no accidental rupture of membranes. Mean fetal oxygen saturation was 76.1 +/- 6.2%. CONCLUSIONS This study has shown that antepartum fetal pulse oximetry is feasible once a specially designed probe and signal analysis system are used.

P11.12: Determination of fetal head station during labor—an innovative method combining ultrasound and spatial positioning

predictor of post-term pregnancy (defined as a pregnancy that extended beyond 41 + 3 weeks of gestation) in nulliparous women. Methods: This prospective observational study enrolled 122 consecutive nulliparous women with singleton gestations at 37 weeks. Cervical length was measured by transvaginal ultrasonography at 20 to 24 weeks and 37 weeks. Analysis was conducted with Fisher’s exact test, Mann-Whitney U test, and receiver operating characteristic curve analysis. Results: 1) Post-term pregnancy occurred in 17% (21/122) of the women delivered at or beyond term. 2) The mean (± standard deviation) cervical lengths at 20 to 24 weeks and 37 weeks were 39 ± 5.6 mm and 28 ± 6.4 mm, respectively. 3) Cervical length at 37 weeks, but not at 20 to 24 weeks, was significantly longer in women delivered at > 41 + 3 weeks than in those delivered at ≤ 41 + 3 weeks (median 33 mm, range 18 to 44 mm vs median 28 mm, range 11 to 42 mm; p < 0.005). 4) There was a significant correlation between cervical length at 37 weeks and gestational age at delivery (Pearson correlation coefficient, r = 0.394, p < 0.0001). 5) In the receiver operating characteristic curves, the best cut-off value of cervical length at 37 weeks for the prediction of post-term pregnancy was 30 mm, with a sensitivity of 70% and a specificity of 59%. Conclusions: Cervical length assessed by transvaginal ultrasonography at 37 weeks can predict the likelihood of post-term pregnancy in low-risk nulliparous women. However, there is not an association between cervical length at 20 to 24 weeks and the occurrence of post-term pregnancy.

OP11.05: New method for the determination of fetal head position during labor

Objective: Assessment of fetal head station is of importance before instrumental vaginal delivery. We have established a simple method of performing intrapartum infrapubic ultrasound (iiUS). Relating the fetal skull to the symphysis in laboring women during pushing and prior to vacuum extraction, we defined sonographic criteria for successful instrumental vaginal delivery. Methods: Sonographic assessment of the female pelvis in term pregnancies was performed in women with singleton pregnancies in the second stage of labor and after rupture of membranes. Anatomic landmarks were determined sonographically from sagittal infrapubic insonation with a curved array transducer. A 3D CT volume was used to correlate the normal anatomy of the female pelvis with these iiUS-derived landmarks. 20 women with singleton fetuses were studied immediately before vacuum extraction. Results: With a transducer placed infrapubically in a median sagittal orientation (‘infrapubic plane’), landmarks are: (1) the infrapubic line, placed perpendicular to the long axis of the pubic symphysis; (2) the widest fetal head diameter and its movement with regard to the infrapubic line during pushing; and (3) the ‘head direction’ as the angle between the long axis of the symphysis and a line perpendicular to the widest head diameter. CT reconstruction demonstrated the infrapubic line to be 3 cm cranial to the parallel interspinous plane. In 20 vacuum deliveries, the ‘head up’ sign (head pointing ventrally) and objective descent of the fetal head below the infrapubic line, both noted at the height of pushing, were associated with successful delivery. Lack of decent/lack of passage below the infrapubic line and horizontal or even downward head direction were poor prognostic signs. Conclusions: Intrapartum infrapubic ultrasound (iiUS) can provide information about the dynamics of the second stage of labor, head station and head direction. It may be used to assess prognosis for instrumental vaginal delivery.