Placental implantation at 18 weeks and migration throughout pregnancy

SWAVE 2.0 Imaging of Placental Elasticity and Viscosity: Potential Biomarkers for Placenta-Mediated Disease Detection

Pregnancy complications such as pre-eclampsia (PE) and intrauterine growth restriction (IUGR) are associated with structural and functional changes in the placenta. Different elastography techniques with an ability to assess the mechanical properties of tissue can identify and monitor the pathological state of the placenta. Currently available elastography techniques have been used with promising results to detect placenta abnormalities; however, limitations include inadequate measurement depth and safety concerns from high negative pressure pulses. Previously, we described a shear wave absolute vibro-elastography (SWAVE) method by applying external low-frequency mechanical vibrations to generate shear waves and studied 61 post-delivery clinically normal placentas to explore the feasibility of SWAVE for placental assessment and establish a measurement baseline. This next phase of the study, namely, SWAVE 2.0, improves the previous system and elasticity reconstruction by incorporating a multi-frequency acquisition system and using a 3-D local frequency estimation (LFE) method. Compared with its 2-D counterpart, the proposed system using 3-D LFE was found to reduce the bias and variance in elasticity measurements in tissue-mimicking phantoms. In the aim of investigating the potential of improved SWAVE 2.0 measurements to identify placental abnormalities, we studied 46 post-delivery placentas, including 26 diseased (16 IUGR and 10 PE) and 20 normal control placentas. By use of a 3.33-MHz motorized curved-array transducer, multi-frequency (80,100 and 120 Hz) elasticity measures were obtained with 3-D LFE, and both IUGR (15.30 ± 2.96 kPa, p = 3.35e^-5) and PE (12.33 ± 4.88 kPa, p = 0.017) placentas were found to be significantly stiffer compared with the control placentas (8.32 ± 3.67 kPa). A linear discriminant analysis (LDA) classifier was able to classify between healthy and diseased placentas with a sensitivity, specificity and accuracy of 87%, 78% and 83% and an area under the receiver operating curve of 0.90 (95% confidence interval: 0.8-0.99). Further, the pregnancy outcome in terms of neonatal intensive care unit admission was predicted with a sensitivity, specificity and accuracy of 70%, 71%, 71%, respectively, and area under the receiver operating curve of 0.78 (confidence interval: 0.62-0.93). A viscoelastic characterization of placentas using a fractional rheological model revealed that the viscosity measures in terms of viscosity parameter n were significantly higher in IUGR (2.3 ± 0.21) and PE (2.11 ± 0.52) placentas than in normal placentas (1.45 ± 0.65). This work illustrates the potential relevance of elasticity and viscosity imaging using SWAVE 2.0 as a non-invasive technology for detection of placental abnormalities and the prediction of pregnancy outcomes.

Placental Location in Maternal-Fetal Surgery for Myelomeningocele

INTRODUCTION

Uterine incision based on placental location in open maternal-fetal surgery (OMFS) has never been evaluated in regards to maternal or fetal outcomes.

OBJECTIVE

To investigate whether an anterior placenta was associated with increased rates of intraoperative, perioperative, antepartum, obstetric, or neonatal complications in mothers and babies who underwent OMFS for myelomeningocele (fMMC) closure.

METHODS

Data from the international multi-center prospective registry of patients who underwent OMFS for fMMC closure (fMMC Consortium Registry, 12/15/2010-7/31/2019) was used to compare fetal and maternal outcomes between anterior and posterior placental locations.

RESULTS

Placental location for 623 patients was evenly distributed between anterior (51%) or posterior (49%). Intraoperative fetal bradycardia (8.3% vs 3.0%, p=0.005) and performance of fetal resuscitation (3.6% vs 1.0%, p=0.034) occurred more frequently in cases with an anterior placenta when compared to those with a posterior placenta. Obstetric outcomes including membrane separation, placental abruption, and spontaneous rupture of membranes were not different among the two groups. However, thinning of the hysterotomy site (27.7% vs 17.7%, p=0.008) occurred more frequently in cases of anterior placenta. Gestational age at delivery (p=0.583) and length of stay in the neonatal intensive care unit (p=0.655) were similar between the two groups. Fetal incision dehiscence and wound revision were not significantly different between groups. Critical clinical outcomes including fetal demise, perinatal death, and neonatal death were all infrequent occurrences and not associated with placental location.

CONCLUSIONS

Anterior placental location is associated with increased risk of intraoperative fetal resuscitation and increased thinning at the hysterotomy closure site. Individual institutional experiences may have varied but the aggregate data from the fMMC Consortium did not show a significant impact on the gestational age at delivery or maternal or fetal clinical outcomes.

Placental location site and adverse antepartum pregnancy complications: a meta-analysis and review of the literature

PURPOSE

The purpose to the study was to determine the relationship, if any, between the placental location site and antepartum complications of pregnancy.

METHODS

A University research librarian conducted a comprehensive literature search using the search engines PubMed and Web of Science. The search terms were "placental location" AND "pregnancy complications" OR "perinatal complications. There were no limits put on the years of the search.

RESULTS

The search identified 110 articles. After reviewing all the abstracts, relevant full articles, and references of full articles, there were 22 articles identified specific to antepartum complications. Central + fundal locations compared to all lateral were associated with a lower risk of hypertension during pregnancy RR = 0.47, 95% CI: 0.31-0.71]. Central location compared to all lateral was also associated with lower risk of hypertension during pregnancy [RR = 0.39, 95% CI: 0.26-0.59]. Placenta locations in the lower uterine segment were associated with greater risk of antepartum hemorrhage (APH) [RR = 2.99, 95% CI: 1.16-7.75] compared to above the lower uterine segment. No differences were observed in placental locations and gestational diabetes (GDM), preterm prelabor rupture of membranes (PPROM), preterm delivery (PTD) or on a placental abruption.

CONCLUSION

Central and fundal location sites and central location alone decreased the risk of hypertension during pregnancy. Low uterine segment location sites increased the risk for APH. There were no effects of placenta location sites on the development of GDM, PPROM, PTD or abruption.

Relationship between placenta location and resolution of second trimester placenta previa

This prospective study was conducted to assess the rate of resolution of second trimester placenta previa in women with anterior placenta and posterior placenta, and that in women with and without previous cesarean section. In this study, placenta previa was defined as a placenta lying within 20 mm of the internal cervical os or overlapping it. We recruited 183 women diagnosed with previa between 20⁺⁰ weeks and 25⁺⁶ weeks. They were grouped according to their placenta location (anterior or posterior) and history of cesarean section. Comparative analysis was performed on demographic data, resolution rate of previa and pregnancy outcomes between anterior group and posterior group, and on those between cesarean section group and non-cesarean section group. Women with an anterior placenta tended to be advanced in parity (P=0.040) and have increased number of dilatation and curettage (P=0.044). The women in cesarean section group were significantly older (P=0.000) and had more parity (P=0.000), gravidity (P=0.000), and dilatation and curettage (P=0.048) than in non-cesarean section group. Resolution of previa at delivery occurred in 87.43% women in this study. Women with a posterior placenta had a higher rate of resolution (P=0.030), while history of cesarean section made no difference. Gestational age at resolution was earlier in posterior group (P=0.002) and non-cesarean section group (P=0.008) than in anterior group and cesarean section group correspondingly. Placenta location and prior cesarean section did not influence obstetric outcomes and neonatal outcomes. This study indicates that it is more likely to have subsequent resolution of the previa when the placenta is posteriorly located for women who are diagnosed with placenta previa in the second trimester.

Placental location and pregnancy outcome

OBJECTIVE

The purpose of this study was to determine if placental location is associated with adverse pregnancy outcome and to assess whether any association exists between different blood groups and location of the placenta.

MATERIAL AND METHODS

Medical records of women were reviewed retrospectively and placental position as documented in the case notes at routine antenatal (20-38 weeks) ultrasonography was identified. Placental position was categorised as anterior, posterior and fundal. Association of placental location with foeto-maternal outcome and different blood groups was noted.

RESULTS

A total 474 case notes of women were analysed for placental location, feto-maternal outcome and blood groups. Anterior placenta was found to have a relation with a greater risk of pregnancy-induced hypertension, gestational diabetes mellitus and placental abruption (p<0.001), while posterior placenta had a significant association with preterm labour (p<0.001). Regarding foetal outcome, an anterior placenta was significantly associated with intrauterine growth retardation and intrauterine foetal death (p<0.001). The majority (54%) of women with an anterior placenta were O-positive blood group, while 46% of women in the posterior placenta group were A-positive blood group (p<0.001).

CONCLUSION

Anterior placental implantation is associated with an increased risk of pregnancy-induced hypertension, gestational diabetes mellitus, placental abruption, intrauterine growth retardation and intrauterine foetal death. Posterior placenta has a significant association with preterm labour and A-positive blood group. Anterior placenta is common in women with O-positive blood group. Placental location may be an important determinant of pregnancy outcome.

Does the presence of a cesarean section scar influence the site of placental implantation and subsequent migration in future pregnancies: a prospective case-control study

OBJECTIVES

To describe placental location in the first trimester of pregnancy and subsequent placental migration in women with and without a history of previous cesarean delivery.

METHODS

In this prospective case-control study, placental location was defined according to five anatomical sites in relation to the endometrial cavity. Placental localization was carried out by transabdominal ultrasound between 11 and 14 weeks' gestation. We recruited 738 women who had undergone one or more previous cesarean sections (CS) and 1856 patients without previous cesarean delivery. Comparative analysis was performed of placental location between the two groups, and to assess placental migration of those classified as being low lying at 20 and 32 weeks' gestation.

RESULTS

There were significant differences in placental location between the two groups. In the CS group there were significantly more posterior and fewer fundal placentae than in the control group (47.2 vs 31.5% and 4.7 vs 15.5%, respectively). The number of previous cesarean deliveries did not have a significant effect on placental location. There was no significant difference in the incidence of anterior low-lying placenta between groups (1.5 vs 0.9%). Placental migration of the low-lying subtypes was similar in both groups (62 vs 64%).

CONCLUSION

The presence of CS scars in the uterus are associated with an increase in the number of posterior placentae and a reduced number that implant in the fundus of the cavity. Migration of a low-lying placenta is independent of the presence of a CS scar in the uterus.

Resolution of complete placenta previa: does prior cesarean delivery matter?

OBJECTIVES

The purpose of this study was to prospectively assess the rate of resolution of complete placenta previa diagnosed at second-trimester sonography in patients with and without previous cesarean delivery.

METHODS

This prospective study evaluated patients at 3 institutions with complete placenta previa diagnosed at second-trimester screening sonography. All patients were followed with sonography every 4 to 6 weeks until either resolution of the previa or delivery occurred. Patients with persistent/nonresolving complete placenta previa underwent cesarean delivery.

RESULTS

A total of 67 patients were enrolled in the study; 18 patients had a prior cesarean delivery. Resolution of placenta previa occurred in 11 of 18 patients (61%) with a prior cesarean delivery, whereas 44 of 49 patients (90%) without a prior cesarean delivery had resolution of placenta previa (P = .012, Fisher exact test). Placental location per se (anterior or posterior) was not associated with resolution of placenta previa (P = .22). Complete placenta previa persisted to delivery in 5 of 9 patients (56%) with a prior cesarean delivery and an anterior placental location.

CONCLUSIONS

This prospective study indicates that patients with a prior cesarean delivery and complete placenta previa diagnosed at second-trimester sonography are less likely to have subsequent resolution of the previa when compared to those without a history of cesarean delivery.

Difference in migration of placenta according to the location and type of placenta previa

PURPOSE

To correlate the incidence and rate of placental migration with the mode of delivery, pregnancy outcome, and maternal complication according to the location (anterior versus posterior) and type of placenta previa (PP).

METHODS

We prospectively evaluated the placentas of 98 pregnant women with PP or low-lying placenta (LLP) at the prenatal sonographic examination performed between 20 and 27 gestational weeks. We divided the pregnant women into groups according to type and location of PP. Follow-up sonographic examination was performed between 32 and 37 weeks. We compared incidence of migration to the normal position and calculated the migration rate as the migrated distance divided by the weeks of interval between 2 sonographic examinations. We compared the incidences of cesarean section, fetal outcome, and maternal complications during the pregnancy.

RESULTS

The incidence of migration in the group of anterior placentas was significantly higher than that in the group of posterior placentas. The mean migration rate in the anterior group was 2.6 mm/week, whereas that in the posterior group was 1.6 mm/week. The migration rate of incomplete PP was significantly higher than that of LLP. Incidence of cesarean section for nonmigrated PP was significantly higher in the posterior group. The incidences of premature delivery and vaginal spotting were also significantly higher in the posterior group.

CONCLUSION

Anterior PP and LLP may migrate more often and faster than posterior PP. Our results may be useful for planning of prenatal management and counseling patients with PP and LLP.

Intrauterine growth restriction and placental location

OBJECTIVE

The purpose of this study was to determine whether an association exists between intrauterine growth restriction (IUGR) and second-trimester placental location.

METHODS

A case-control study was performed in well-dated singleton pregnancies with (n = 67) and without (n = 205) IUGR (defined as estimated fetal weight <10th percentile for gestational age at the last sonographic examination) to investigate the association between IUGR and placental location. Placental location was determined by sonography at 16 to 20 weeks' gestation. Maternal, perinatal, and delivery characteristics were abstracted from medical records. Group comparisons were made by the Student t test, chi(2) analysis, the Fisher exact test, the Wilcoxon test, and analysis of variance. Multivariable logistic regression analysis was used to determine the relationship between IUGR and placental location.

RESULTS

In both groups, the most common placental locations in the second trimester were anterior and posterior. After adjusting for potential confounders (including race, chronic hypertension, and hypertensive disorders of pregnancy), IUGR pregnancies were nearly 4-fold more likely to have lateral placentation (odds ratio, 3.8; 95% confidence interval, 1.3-11.2) compared with anterior or posterior placentation.

CONCLUSIONS

Pregnancies complicated by IUGR are significantly more likely than non-IUGR pregnancies to have lateral placentation in the second trimester.

Second trimester placental location as a predictor of an adverse pregnancy outcome

OBJECTIVE

To determine if the second trimester placental location is associated with perinatal outcomes.

MATERIALS AND METHODS

Observational study of placental location and the subsequent risk of an adverse pregnancy outcome. Placental location was divided into three categories, low, high lateral and high fundal.

RESULTS

There were 3336 pregnancies analyzed in this study. Low implantation sites had a greater risk of preterm labor (odds ratio (OR) 1.70, 95% confidence interval (CI) 1.38 to 2.90, P<0.001), preterm delivery (OR 1.86, 95% CI 1.36 to 2.54, P<0.001), fewer fetuses with macrosomia (OR 0.56, 95% CI 0.38 to 0.83, P=0.010) and reduced risk of postpartum hemorrhage (OR 0.56, 95% CI 0.46 to 0.95, P=0.026). High lateral implantations had a greater risk of low 1-min (OR 1.80, 95% CI 1.11 to 2.93, P=0.017) and 5-min (OR 3.49, 95% CI 1.46 to 8.36, P=0.005) Apgar scores.

CONCLUSIONS

Low placental implantation was associated with an increased risk of preterm labor, preterm delivery and a reduced risk of postpartum hemorrhage, and of a macrosomic fetus. High lateral implantation was associated with low Apgar scores.