Uterine electrical activity, oxytocin and labor: translating electrical into mechanical

PURPOSE

Uterine activity plays a crucial role in labor, especially when utero-tonic materials are administered. We aimed to determine the electrical responsiveness of the uterine musculature to labor augmentation with oxytocin using electrical uterine myography (EUM) technology, and to assess whether the kinetics of the EUM device may serve as a predictor for successful vaginal delivery.

METHODS

EUM prospectively measured electrical uterine activity in women with singleton gestations at term (≥ 37 + 0 weeks) undergoing labor augmentation by oxytocin administration. The results were reported as the EUM index, which represented the mean electrical activity in 10-min intervals and measured in units of microwatt per second (mW/s). Measurements were performed at least 30 min before oxytocin initiation and until at least four contractions per 10 min were recorded by standard tocodynamometry. The delta EUM index was defined as the difference between the mean EUM index before and after the initiation of oxytocin.

RESULTS

The mean EUM index increased significantly during oxytocin augmentation in all the parturients (P < 0.001). Mean and minimum (but not maximum) uterine electrical activity during oxytocin infusion correlated with the baseline uterine activity. The delta EUM index was not significantly affected by demographic or obstetric parameters. There was no correlation between the delta EUM index and time to delivery or the mean EUM index during oxytocin administration and time to delivery.

CONCLUSIONS

Uterine electrical activity as evaluated by EUM is significantly intensified following oxytocin administration, regardless of obstetrical characteristics, and is correlated with the baseline uterine electrical activity prior to oxytocin infusion.

Can middle cerebral artery peak systolic velocity predict polycythemia in monochorionic-diamniotic twins? Evidence from a prospective cohort study

OBJECTIVE

The antenatal diagnosis of twin anemia-polycythemia sequence (TAPS) in monochorionic-diamniotic (MCDA) twin pregnancies is based on elevated peak systolic velocity in the middle cerebral artery (MCA-PSV) in the donor twin and decreased MCA-PSV in the recipient twin. However, the association between these parameters and polycythemia has not yet been established. The aim of this study was to determine whether MCA-PSV can predict polycythemia in MCDA pregnancies.

METHODS

This was a prospective cohort study of MCDA pregnancies recruited at 14-18 weeks' gestation from a single tertiary care center between January 2011 and June 2014. Fetal MCA Doppler waveforms were recorded every 2 weeks from 18 weeks' gestation until delivery. Only those with an MCA-PSV measurement within 1 week of delivery were included in the analysis. Neonatal hematocrit level was determined in all twins from venous blood obtained within 4 h of delivery. Polycythemia was defined as a hematocrit of > 65%, and anemia as a hematocrit of < 45%. TAPS was diagnosed when an intertwin hemoglobin difference of > 8 g/dL and reticulocyte count ratio of > 1.7 were observed.

RESULTS

Of 162 MCDA pregnancies followed during the study period, 69 had an MCA-PSV measurement within 1 week of delivery and were included in the study. Twenty-five neonates were diagnosed with polycythemia and nine twin pairs met the criteria for TAPS. In a pooled analysis, MCA-PSV was negatively correlated with neonatal hematocrit (P = 0.017, r = -0.215) and was significantly higher in anemic fetuses than in normal controls (1.15 multiples of the median (MoM) vs 1.02 MoM, respectively; P = 0.001). However, MCA-PSV was similar among polycythemic and normal fetuses (0.95 MoM vs 1.02 MoM, respectively; P = 0.47). Intertwin difference in MCA-PSV (delta MCA-PSV) was positively correlated with intertwin hematocrit difference (P = 0.002, r = 0.394). Moreover, twin pregnancies with an intertwin hematocrit difference of > 24% had a significantly greater delta MCA-PSV than did those with an intertwin hematocrit difference of ≤ 24% (delta MCA-PSV, 19 vs 5 cm/s; P < 0.001).

CONCLUSIONS

MCA-PSV is not significantly decreased in polycythemic MCDA twins. However, delta MCA-PSV is associated with a large intertwin difference in hematocrit, and its use may be better than conventional methods for the risk assessment of TAPS. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Association of fetal biparietal diameter with mode of delivery and perinatal outcome

OBJECTIVE

To determine the association between sonographic assessment of fetal biparietal diameter (BPD) and pregnancy outcome.

METHODS

This was a retrospective cohort study of pregnancies at 37-42 weeks of gestation which had antepartum sonographic measurement of BPD within 7 days before delivery. Eligibility was limited to singleton pregnancies with neither known structural or chromosomal abnormalities nor prelabor Cesarean delivery (CD). The association of BPD with outcome was analyzed using multivariate logistic regression, receiver-operating characteristics curves and stratification according to BPD quartiles.

RESULTS

In total, 3229 women were eligible for analysis, of whom 2483 (76.9%) had a spontaneous vaginal delivery (SVD), 418 (12.9%) underwent operative vaginal delivery (OVD) and 328 (10.2%) underwent CD. The mean BPD in the obstetric intervention groups (OVD and CD) was significantly higher than that in the SVD group (P < 0.001). After adjusting for confounders, increased BPD was an independent risk factor such that higher values of BPD were associated with progressively higher risk of obstetric intervention (adjusted odds ratio, 1.05 for each 1-mm increase in BPD (95% CI, 1.02-1.09)), but no clear cut-off value for obstetric intervention was found. The fourth quartile group (BPD ≥ 97 mm) was associated with a significantly lower SVD rate (P < 0.001) and higher OVD rate (P = 0.04), relative to the first (BPD 88-90 mm) and second (BPD 91-93 mm) quartile groups, with no apparent adverse impact on immediate neonatal outcome.

CONCLUSIONS

Increased BPD within the week prior to delivery is an independent risk factor such that higher values of BPD are associated with progressively higher risk of obstetric intervention; however, in our experience, no adverse neonatal outcome resulted from such intervention. Thus, increased BPD should not discourage a trial of vaginal delivery.

Selective reduction in complicated monochorionic twins: prediction of obstetric outcome and comparison of techniques

OBJECTIVES

To compare the outcomes of radiofrequency ablation (RFA) and bipolar cord coagulation (BPC) methods for selective feticide in complicated monochorionic (MC) twin gestations and to determine risk factors for adverse pregnancy outcome.

METHODS

This was a retrospective cohort study of all patients with complicated MC twin pregnancy who underwent selective reduction in a single tertiary care center between 2000 and 2014. We compared the two methods with respect to various demographic, obstetric and perinatal outcome variables.

RESULTS

Fifty-three selective terminations in complicated MC twin gestations were performed, 36 by RFA and 17 by BPC. Each technique resulted in a similar overall survival rate of the remaining twin (88.9% vs 76.5%, P = 0.25). Likewise, the mean procedure-to-delivery interval, the rate of spontaneous preterm delivery < 37, < 34, < 32 and < 28 weeks and the rate of preterm prelabor rupture of the membranes did not differ between the groups. However, among patients in the BPC group, there was a trend towards earlier gestational age at delivery (31.3 vs 35.0 weeks, P = 0.09) compared with in the RFA group. There was selective reduction by RFA due to selective intrauterine growth restriction (sIUGR) in 19 cases, 17 (89.5%) of which survived perinatally, with delivery at a median gestational age of 37 weeks. There were no significant differences in perinatal outcome, irrespective of whether the procedure was performed pre- or post-viability. All post-viability reductions, most of which were by RFA, resulted in perinatal survival.

CONCLUSIONS

Perinatal outcome of complicated MC twin gestations undergoing selective feticide seems to be similar regardless of whether termination is by BPC or RFA. Nevertheless, RFA appears to be particularly useful in MC twins complicated by sIUGR and in cases requiring selective reduction beyond the age of viability.