Ultrasonic features of preeclampsia

To ignore or not to ignore placental calcifications on prenatal ultrasound: a systematic review and meta-analysis

OBJECTIVE

The human placenta is known to calcify with advancing gestational age, and, in fact, the presence of significant calcifications is one of the components of grade III placenta, typical of late gestation. As such, the presence of significant placental calcifications often prompts obstetric providers to expedite delivery. This practice has been attributed, in part, to the presumed association between grade III placenta and adverse pregnancy outcomes. Such approach, however, can be the source of major anxiety and may lead to unnecessary induction of labor, with its associated predisposition to cesarean delivery as well as a myriad of maternal and neonatal morbidities. The objective of this study was to examine the association between grade III placental calcifications and pregnancy outcomes.

MATERIALS AND METHODS

A systematic review of the literature was performed for studies evaluating the association between grade III placenta and a number of pregnancy outcomes, including labor induction, fetal distress (abnormal fetal heart tracing), low Apgar score (less than 7 at 5 min), need for neonatal resuscitation, admission to the Neonatal Intensive Care Unit, perinatal death, meconium liquor, and low birth weight.

RESULTS

There was a five-fold increase in risk of labor induction with the presence of grade III placenta (OR 5.41; 95% CI 2.98-9.82). There was no association between grade III placenta and the incidence of abnormal fetal heart tracing (OR 1.62; 95% CI 0.94-2.78), low Apgar score of less than 7 at 5 min (OR 1.68; 95% CI 0.84-3.36), need for neonatal resuscitation (OR 1.08; 95% CI 0.67-1.75), and admission to the Neonatal Intensive Care Unit (OR 0.90; 95% CI 0.21-3.74). In turn, the incidence of meconium liquor was higher in the setting of grade III placentae (OR 1.68; 95% CI 1.17-2.39). Similarly, a positive association between grade III placental calcifications and low birth weight (OR 1.63; 95% CI 1.19-2.22) and perinatal death (OR 7.41; 95% CI 4.94-11.09) was identified.

CONCLUSION

The study alerts us to a significant association between grade 3 placental calcifications and labor induction, although it demonstrates that these sonographic findings do not appear to predispose to fetal distress, low Apgar score, need for neonatal resuscitation, or admission to the NICU.

Computerized assessment of placental calcification post-ultrasound: a novel software tool

OBJECTIVES

Placental calcification is associated with an increased risk of perinatal morbidity and mortality. The subjectivity of current ultrasound methods of assessment of placental calcification indicates that a more objective method is required. The aim of this study was to correlate the percentage of calcification defined by the clinician using a new software tool for calculating the extent of placental calcification with traditional ultrasound methods and with pregnancy outcome.

METHODS

Ninety placental images were individually assessed. An upper threshold was defined, based on high intensity, to quantify calcification within the placenta. Output metrics were then produced including the overall percentage of calcification with respect to the total number of pixels within the region of interest. The results were correlated with traditional ultrasound methods of assessment of placental calcification and with pregnancy outcome.

RESULTS

The results demonstrate a significant correlation between placental calcification, as defined using the software, and traditional methods of Grannum grading of placental calcification. Whilst correlation with perinatal outcome and cord pH was not significant as a result of small numbers, patients with placental calcification assessed using the computerized software at the upper quartile had higher rates of poor perinatal outcome when compared with those at the lower quartile (8/22 (36%) vs 3/23 (13%); P = 0.069).

CONCLUSION

These results suggest that this computerized software tool has the potential to become an alternative method of assessing placental calcification.

No correlation between ultrasound placental grading at 31-34 weeks of gestation and a surrogate estimate of organ function at term obtained by stereological analysis

We test the experimental hypothesis that early changes in the ultrasound appearance of the placenta reflect poor or reduced placental function. The sonographic (Grannum) grade of placental maturity was compared to placental function as expressed by the morphometric oxygen diffusive conductance of the villous membrane. Ultrasonography was used to assess the Grannum grade of 32 placentas at 31-34 weeks of gestation. Indications for the scans included a history of previous fetal abnormalities, previous fetal growth problems or suspicion of IUGR. Placentas were classified from grade 0 (most immature) to grade III (most mature). We did not exclude smokers or complicated pregnancies as we aimed to correlate the early appearance of mature placentas with placental function. After delivery, microscopical fields on formalin-fixed, trichrome-stained histological sections of each placenta were obtained by multistage systematic uniform random sampling. Using design-based stereological methods, the exchange surface areas of peripheral (terminal and intermediate) villi and their fetal capillaries and the arithmetic and harmonic mean thicknesses of the villous membrane (maternal surface of villous trophoblast to adluminal surface of vascular endothelium) were estimated. An index of the variability in thickness of this membrane, and an estimate of its oxygen diffusive conductance, were derived secondarily as were estimates of the mean diameters and total lengths of villi and fetal capillaries. Group comparisons were drawn using analysis of variance. We found no significant differences in placental volume or composition or in the dimensions or diffusive conductances of the villous membrane. Subsequent exclusion of smokers did not alter these main findings. Grannum grades at 31-34 weeks of gestation appear not to provide reliable predictors of the functional capacity of the term placenta as expressed by the surrogate measure, morphometric diffusive conductance.

Ultrasonic evidence of placental calcification at 36 weeks' gestation: maternal and fetal outcomes

BACKGROUND

To determine the significance of an inappropriately mature placenta on ultrasound examination (Grannum classification), in a low-risk obstetric population. Scans were performed at 36 weeks' gestation. The study group comprised patients demonstrating a grade III placenta, and the control group comprised patients not demonstrating a grade III placenta.

METHODS

A total of 1802 low-risk patients were scanned using serial directed real-time ultrasound at 36 weeks' gestation to determine placental maturity.

RESULTS

The incidence of a grade III placenta at 36 weeks' gestation was 3.8% (68/1802). A grade III placenta was associated with young maternal age and cigarette smoking, p < 0.01. The incidence of proteinuric pregnancy-induced hypertension in the study and control groups was 7.4% (5/68) and 1.56% (27/1734), respectively, p < 0.01. The proportion of infants with a weight less than the 10th centile at birth in the study and control groups was 17.6% (12/68) and 5.6% (97/1734), respectively, p < 0.01.

CONCLUSIONS

Ultrasound detection of a grade III placenta at 36 weeks' gestation in a low-risk population helps to identify the "at-risk" pregnancy. It helps to predict subsequent development of proteinuric pregnancy-induced hypertension and may help in identifying the growth-restricted baby.

Real-time ultrasound of the placenta in assessment of fetal pulmonic maturity

The use of ultrasound is a noninvasive method of assessing fetal maturity. However, in order for it to be a substitute for amniocentesis, a high degree of accuracy is required. Static ultrasound examination of placental development has revealed certain patterns of maturity which have suggested to be predictors of fetal pulmonary maturity. This study analyzes 100 patients near term for the accuracy of placental grade in predicting pulmonary maturity when measured by the lecithin/sphingomyelin ratio and by clinical development of the respiratory distress syndrome in the neonate. A mature placental grade (Grade III) determined by real-time sonography corresponded to fetal lung maturity in all cases (n = 15). Placental grade as determined by this methodology appeared to be an accurate predictor of fetal maturity in the population examined.