Placental thickness-to-estimated foetal weight ratios and small-for-gestational-age infants at delivery

Ultrasonographic assessment of abnormal fetal growth related to uteroplacental-fetal biometrics and Doppler (U-AID) indices: Protocol for multicenter retrospective cohort study trial

Fetal growth restriction (FGR) is one of the leading causes of perinatal morbidity and mortality. Many studies have reported an association between FGR and fetal Doppler indices focusing on umbilical artery (UA), middle cerebral artery (MCA), and ductus venosus (DV). The uteroplacental-fetal circulation which affects the fetal growth consists of not only UA, MCA, and DV, but also umbilical vein (UV), placenta and uterus itself. Nevertheless, there is a paucity of large-scale cohort studies that have assessed the association between UV, uterine wall, and placental thickness with perinatal outcomes in FGR, in conjunction with all components of the uteroplacental-fetal circulation. Therefore, this multicenter study will evaluate the association among UV absolute flow, placental thickness, and uterine wall thickness and adverse perinatal outcome in FGR fetuses. This multicenter retrospective cohort study will include singleton pregnant women who undergo at least one routine fetal ultrasound scan during routine antepartum care. Pregnant women with fetuses having structural or chromosomal abnormalities will be excluded. The U-AID indices (UtA, UA, MCA, and UV flow, placental and uterine wall thickness, and estimated fetal body weight) will be measured during each trimester of pregnancy. The study population will be divided into two groups: (1) FGR group (pregnant women with FGR fetuses) and (2) control group (those with normal growth fetus). We will assess the association between U-AID indices and adverse perinatal outcomes in the FGR group and the difference in U-AID indices between the two groups.

Placental volume, thickness and transverse relaxation time (T2*) estimated by magnetic resonance imaging in relation to small for gestational age at birth

INTRODUCTION

Placental magnetic resonance imaging (MRI) may be a valuable tool in the prediction of small for gestational age (SGA) at birth. MRI provides reliable estimates of placental volume and thickness. In addition, placental transverse relaxation time (T2*) may be directly related to placental function. This study aimed to explore and compare the predictive performance of three placental MRI parameters - volume, thickness and T2* - in relation to SGA at birth.

METHODS

A mixed cohort of 85 pregnancies was retrieved from the placental MRI database at the study hospital. MRI was performed in a 1.5 T system at gestational weeks 15-41. In normal birthweight (BW) pregnancies [BW > -22 % of expected for gestational age (GA)], the correlation between each of the MRI parameters and GA was investigated by linear regression. The prediction of SGA was investigated by logistic regression analysis adjusted for GA at MRI.

RESULTS

In normal BW pregnancies, a significant linear correlation was found between GA and each of the MRI parameters. Univariate analysis demonstrated that placental volume [odds ratio (OR) 0.97, p = 0.001] and placental T2* (OR 0.79, p = 0.003), but not placental thickness (OR 0.92, p = 0.862) were significant predictors of SGA. A multi-variate model including all three MRI parameters found that placental T2* was the only independent predictor of SGA (OR 0.81, p = 0.04).

CONCLUSION

Among the MRI parameters investigated in this study, placental T2* was the only independent predictor of SGA in a multi-variate model. This finding underlines the strong position of T2*-weighted placental MRI in the prediction of SGA.

Developmental Ultrasound Characteristics in Guinea Pigs: Similarities with Human Pregnancy

BACKGROUND

Biometrical and blood flow examinations are fundamental for assessing fetoplacental development during pregnancy. Guinea pigs have been proposed as a good model to study fetal development and related gestational complications; however, longitudinal growth and blood flow changes in utero have not been properly described. This study aimed to describe fetal and placental growth and blood flow of the main intrauterine vascular beds across normal guinea pig pregnancy and to discuss the relevance of this data for human pregnancy.

METHODS

Pregnant guinea pigs were studied from day 25 of pregnancy until term (day ~70) by ultrasound and Doppler assessment. The results were compared to human data from the literature.

RESULTS

Measurements of biparietal diameter (BPD), cranial circumference (CC), abdominal circumference, and placental biometry, as well as pulsatility index determination of umbilical artery, middle cerebral artery (MCA), and cerebroplacental ratio (CPR), were feasible to determine across pregnancy, and they could be adjusted to linear or nonlinear functions. In addition, several of these parameters showed a high correlation coefficient and could be used to assess gestational age in guinea pigs. We further compared these data to ultrasound variables from human pregnancy with high similarities.

CONCLUSIONS

BPD and CC are the most reliable measurements to assess fetal growth in guinea pigs. Furthermore, this is the first report in which the MCA pulsatility index and CPR are described across guinea pig gestation. The guinea pig is a valuable model to assess fetal growth and blood flow distribution, variables that are comparable with human pregnancy.

Thick Placenta in Pregnancy: A Review

Importance

A thickened placenta is easily identified on ultrasound and provides insight into maternal and fetal wellbeing as well as underlying structural and physiologic anomalies.

Objectives

The aim of this study was to review the literature to clarify what classifies a placenta as "thickened" and to review the associated incidence, maternal and fetal comorbidities, and management during pregnancy.

Evidence Acquisition

Electronic databases (PubMed and Web of Science) were searched from 2000 to 2020 in the English language. Studies were selected that examined associations between placental thickness, potential etiologies, and obstetric outcomes.

Results

There were 140 abstracts identified. After reviewing the articles, 60 were used in this review. Routine assessment of the placenta in the prenatal period is an easy and inexpensive way to assess the maternal and fetal patients. The criteria for a "thickened placenta" vary between studies based on gestational age, placental location, measurement technique, and maternal or fetal factors. Whereas most suggest thickness exceeding 4 cm is pathologic, a review had a threshold of 6 cm in the third trimester to classify placentomegaly. Several maternal and fetal conditions have been associated with a thickened placenta, such as obesity, parity, anemia, diabetes, preeclampsia, cardiac dysfunction, infection, assisted reproductive technology, multiple pregnancy, sacrococcygeal teratomas, and Beckwith-Wiedemann syndrome. A thickened placenta in pregnancy is associated with a higher incidence of adverse pregnancy outcomes and neonatal morbidity and mortality.

Conclusions

The literature is clear that early evaluation of the placenta using ultrasound should be a standard practice. A thickened placenta found on routine imaging should prompt a more thorough investigation to determine the etiology of the placentomegaly. At the time of this literature review, there are no recommendations regarding modality or frequency of antenatal surveillance in pregnancies complicated by a thickened placenta. However, serial ultrasounds and weekly antenatal testing in the third trimester should be considered.

Relevance

A thickened placenta has been associated with a variety of maternal and fetal conditions and increases the risk of adverse pregnancy outcomes and neonatal morbidity and mortality.

Ultrasonographic placental thickness versus fetal outcome: A prospective study in Southern India

Background:

Variations in placental thickness are associated with increased perinatal morbidity and mortality. However, only very few studies have been established on the correlation between placental thickness with birth outcomes. This study correlated placental thickness in 2^nd and 3^rd trimesters with neonatal outcome, maternal weight gain, and body mass index (BMI).

Methods:

A total of 116 patients aged between 20 to 50 years with singleton pregnancy and regular menstrual history (and sure about their last menstrual period) were included. Placental thickness was measured at 24 and 36 weeks by ultrasound and was divided into three groups: Group A (normal placenta), Group B (thin placenta), and Group C (thick placenta); and correlated with neonatal outcome, maternal weight gain, and BMI.

Results:

Out of the 116 pregnant women, 55 (47.4%) were primigravida and 61 (52.6%) were multigravida. Six patients (3.6%) delivered pre-term before 36 weeks. In the 2^nd and 3^rd trimesters, most cases had normal placental thickness (Group A; 93.1% and 92.7%), followed by thin placenta (Group B; 5.2% and 7.3%) and thick placenta (Group C; 1.7% and 0), respectively. Two patients with thin placenta had neonatal death. A significant positive correlation was found between birth weight and placental thickness (at 24 weeks; 0.516^r, P<0.00001 and at 36 weeks; 0.669^r, P<0.00001) and maternal weight gain and birth weight (0.563^r, P<0.00001).

Conclusion:

Placental thickness on ultrasonography demonstrated well the correlation between birth weight in 2^nd and 3^rd trimesters and increased incidence of antenatal and postpartum complications resulting from thin placenta.

Insights into the role of placenta thickness as a predictive marker of perinatal outcome

The placenta is a transitory organ indispensable for normal fetal maturation and growth. Recognition of abnormal placental variants is important in clinical practice, and a broader understanding of the significance of placental variants would help clinicians better manage affected pregnancies. Increased thickness of the placenta is reported to be a nonspecific finding but it is associated with many maternal and fetal abnormalities, including preeclampsia and abnormal fetal growth. In this review, we address the questions regarding the characteristics of placenta thickness and the relationship between thickened placenta and poor pregnancy outcomes.

Role of 2-Dimensional Ultrasound Imaging in Placental and Umbilical Cord Morphometry: Literature and Pictorial Review

Abnormalities of the placenta and umbilical cord have been associated with adverse pregnancy outcomes. Antenatal detection of placental and umbilical cord abnormalities using ultrasound (US) imaging is now gaining popularity with the advancements in obstetric US. This article reviews the use of 2-dimensional obstetric US as a tool to measure and assess placental and umbilical cord morphometry. It highlights the potential role of placental and umbilical cord morphometry as a valuable component of the screening tool for high risk pregnancies and identifies the need for further research to examine its feasibility.

The volume of villi with γ-sm-actin positive perivascular cells correlates with placental weight and thickness

INTRODUCTION

The classification of histologically stained villous cross sections in villous types (terminal, intermediate and stem villi) by stromal peculiarities is known to be observer predicated. Therefore, quantitative histology of villous trees has not become a routine endpoint of studies on the role of the placenta in prenatal programming, as opposed to the gross placental parameters weight and thickness. The classification of villous cross sections in central (stem) and peripheral (terminal) parts based on the presence or absence, respectively, of immunohistochemical detection of myofibroblasts in perivascular position is less observer dependent. We hypothesized that it will, possibly, identify microscopic correlates of placental weight and thickness within the villous tree.

METHODS

50 placentas from clinically normal pregnancies were processed for the present study. Thin villous cross sections, obtained in a systematic random manner, were stained immunohistochemically to detect γ-smooth muscle (sm) actin and to classify them subsequently as part of central or peripheral villous tree. The volume fractions of histological structures visible in villous cross sections (stroma, lumen, endothelium and syncytium) were estimated by design-based stereology.

RESULTS

The present study reveals a significant correlation of placental weight and thickness with the volume estimate of stroma that have myofibroblasts in perivascular position.

DISCUSSION

The positive linear correlation between the volume of central parts of villous trees and the placental weight and thickness is new. Surprisingly, the volume of more peripheral parts of villous trees, which is the main site of materno-fetal exchange does not correlate with placental weight and thickness.

Role of Ultrasonographic Placental Thickness in Prediction of Fetal Outcome: A Prospective Indian Study

Background Information

Placenta is the connecting organ between the mother and the fetus. It supplies oxygen and all the necessary elements for the growth and development of the fetus. In normal pregnancy, the growth of the placenta remains concordant with the growth of the fetus. The sonographic assessment of placenta can give information about the nutritional status of the fetus. It is known that normal placental thickness approximately equals gestational age. It is historically documented that placental weight is one-fifth of the fetal weight and abnormally thin or thick placenta is associated with increased incidence of perinatal morbidity and mortality. However, there are very few studies correlating placental thickness with Neonatal outcome.

Objectives

To correlate ultrasonographic placental thickness at 32 and 36 weeks pregnancy with neonatal outcome. To propose placental thickness as a simple test for prediction of neonatal outcome.

Methods

Placental thickness at 32 and 36 weeks was measured by ultrasound, in 130 pregnant mothers with confirmed dates and uncomplicated singleton pregnancy. Placental thickness was categorized as normal (10th-95th percentile), thin (<10th percentile) and thick (>95th percentile) at each stage and was correlated with birth weight and neonatal outcome.

Results

Neonatal outcome was good in women with normal placental thickness (10th-95th percentile) at 32 and 36 weeks and was compromised in women with thin (<10th percentile) and thick (>95th percentile) placentae.

Conclusion

Placental thickness at 32 and 36 weeks corresponds well with gestational age and is a good prognostic factor in assessing neonatal outcome. Therefore, placental thickness should be measured in addition to biometric parameters in antenatal women undergoing ultrasound.