Placental site does not change background uterine electromyographic activity in the middle trimester of pregnancy

A Preliminary Exploration of the Placental Position Influence on Uterine Electromyography Using Fractional Modelling

The uterine electromyogram, also called electrohysterogram (EHG), is the electrical signal generated by uterine contractile activity. The EHG has been considered an expanding technique for pregnancy monitoring and preterm risk evaluation. Data were collected on the abdominal surface. It has been speculated the effect of the placenta location on the characteristics of the EHG. In this work, a preliminary exploration method is proposed using the average spectra of Alvarez waves contractions of subjects with anterior and non-anterior placental position as a basis for the triple-dispersion Cole model that provides a best fit for these two cases. This leads to the uterine impedance estimation for these two study cases. Non-linear least square fitting (NLSF) was applied for this modelling process, which produces electric circuit fractional models’ representations. A triple-dispersion Cole-impedance model was used to obtain the uterine impedance curve in a frequency band between 0.1 and 1 Hz. A proposal for the interpretation relating the model parameters and the placental influence on the myometrial contractile action is provided. This is the first report regarding in silico estimation of the uterine impedance for cases involving anterior or non-anterior placental positions.

Cervical length should be measured for women with placenta previa: cohort study

OBJECTIVES

To study the relevance between cervical length (CL) and different maternal/neonatal outcomes in pregnancies complicated with placenta previa/accreta.

METHODS

Three hundred twenty-eight women, who had medically free singleton live pregnancies with the diagnosis of placenta previa and/or accreta, were included and divided regarding their CL into two groups. Threatened preterm labor, maternal tocolysis, multiple gestations, polyhydramnios, ruptured fetal membranes, fetal complications, history of cervical conization, and the presence of cervical cerclage were the exclusion criteria. Demographic data, obstetric history, as well as, the courses of the complicated pregnancies were collected and statistically analyzed.

RESULTS

The short CL group had significantly less distance between the placenta and the internal cervical os (p-value < .001) Also, they showed more ultrasound parameters of complete placenta previa with anterior location (p-value < .001 and .003 respectively) and placental adherence (21.8 versus 41.1%). Women with short cervix had significantly higher rates of preterm birth, antepartum hemorrhage, emergency cesarean sections, intraoperative estimated blood loss, massive bleeding, prevalence of placental adherence and cesarean hysterectomy (p-value < .001 for the entire outcomes). Multivariable binary logistic regression showed that CL (<30 mm) was a significant independent risk factor in prediction of severe hemorrhage, PTB, emergency CS, placental adherence, cesarean hysterectomy (p-value < .001 for adverse maternal outcomes) and low cord Ph (p-value = .016).

CONCLUSIONS

Assessment of the cervical length could be a crucial step in the work-up and decision making for pregnancies complicated with abnormally situated and/or adherent placenta as it is strongly associated with a wide range of maternal and neonatal morbidities.

Type and location of placenta previa affect preterm delivery risk related to antepartum hemorrhage

PURPOSE

To evaluate whether type and location of placenta previa affect risk of antepartum hemorrhage-related preterm delivery.

METHODS

We retrospectively studied 162 women with singleton pregnancies presenting placenta previa. Through observation using transvaginal ultrasound the women were categorized into complete or incomplete placenta previa, and then assigned to anterior and posterior groups. Complete placenta previa was defined as a placenta that completely covered the internal cervical os, with the placental margin >2 cm from the os. Incomplete placenta previa comprised marginal placenta previa whose margin adjacent to the internal os and partial placenta previa which covered the os but the margin situated within 2 cm of the os. Maternal characteristics and perinatal outcomes in complete and incomplete placenta previa were compared, and the differences between the anterior and the posterior groups were evaluated.

RESULTS

Antepartum hemorrhage was more prevalent in women with complete placenta previa than in those with incomplete placenta previa (59.1% versus 17.6%), resulting in the higher incidence of preterm delivery in women with complete than in those with incomplete placenta previa [45.1% versus 8.8%; odds ratio (OR) 8.51; 95% confidence interval (CI) 3.59-20.18; p < 0.001]. In complete placenta previa, incidence of antepartum hemorrhage did not significantly differ between the anterior and the posterior groups. However, gestational age at bleeding onset was lower in the anterior group than in the posterior group, and the incidence of preterm delivery was higher in the anterior group than in the posterior group (76.2% versus 32.0%; OR 6.8; 95% CI 2.12-21.84; p = 0.002). In incomplete placenta previa, gestational age at delivery did not significantly differ between the anterior and posterior groups.

CONCLUSION

Obstetricians should be aware of the increased risk of preterm delivery related to antepartum hemorrhage in women with complete placenta previa, particularly when the placenta is located on the anterior wall.