Placental MRI in intrauterine fetal growth restriction.

OBJECTIVE: Our objectives were to determine if MR imaging of the placenta could demonstrate a specific placental phenotype in small for gestational age fetuses with increasing severity of fetal growth restriction, and if MRI findings at the time of scan could be used to predict fetal or neonatal mortality. METHOD: We included singleton growth restricted fetuses with increasing severity of fetal growth restriction secondary to placental insufficiency. 20 growth restricted fetuses and 28 normal fetuses were scanned once during pregnancy at varying gestations. MRI scans were performed on a 1.5T system using ssFSE sequences through the uterus. Data was collected on the severity of fetal growth restriction and pregnancy outcome, including clinical neonatal details, perinatal mortality, and birthweight and centile. Placental volume, maximal placental thickness, the placental thickness to volume ratio, the placenta to amniotic fluid signal intensity ratio, and the presence of abnormal signal intensity consistent with placental pathology were noted. In a subset of patients, histopathological diagnosis was compared with the MRI appearance of the placenta. RESULTS: There was a significant increase in the placental volume affected by pathology in growth restricted fetuses (p < 0.001). The placental appearance was also thickened and globular, with an increase in the placental thickness to volume ratio (p < 0.001). Although placental volume increased with increasing gestation, it remained reduced in the growth restricted fetuses (p = 0.003). There was a significant correlation between the severity of fetal growth restriction and the placental volume affected by pathology, the placental thickness to volume ratio, and the placental volume. ROC analysis showed that fetal or neonatal death was predicted by the percentage of abnormal signal intensity consistent with placental pathology (p = 0.002). The presence of a thickened, globular placenta and a maximal placental thickness to volume ratio above the 95% confidence limit for gestation was significantly associated with an increased incidence of fetal or neonatal mortality (relative risk = 1.615, p = 0.001 and relative risk = 7, p < 0.001). CONCLUSIONS: The MRI appearance of the placenta provides an indication of the severity and underlying disease process in fetal growth restriction. In units where MRI imaging of the growth restricted fetus occurs, we suggest that the assessment of the placenta should also occur as it may contribute to management decisions in cases at the threshold of viability. It may have a role to play in monitoring disease severity, and the effect of future interventions designed to improve placental function.

Observer accuracy and reproducibility of visual estimation of blood loss in obstetrics: how accurate and consistent are health-care professionals?

OBJECTIVES: To evaluate the observer accuracy and intra-observer test-retest reliability of visual estimation of blood loss by midwives and obstetricians. METHODS: This was a prospective, single-blinded observational study conducted at a London teaching hospital. The accuracy of visually estimating five maternity pads that had been soaked with 25, 50, 100, 150 and 200 ml of blood was assessed. The reproducibility in estimating the same volume (two sets of pads soaked with 50, 100, 150 and 200 ml of blood randomly placed at separate stations) was evaluated by asking participants to visually estimate these volumes. RESULTS: Although there is a tendency to overestimate, the mean percentage difference (estimated-actual volumes) was not significantly different among consultants, trainees and midwives. Visual estimations were especially inaccurate with smaller volumes, which could be overestimated by up to 540%. Test-retest reliability was poor for the larger volumes but statistically acceptable for the smaller volumes, although the difference between the two estimates of the same volume could be as much as 300%. CONCLUSIONS: Visual estimations were inaccurate by health-care professionals who have a tendency to overestimate. Experience did not appear to have a confounding effect on accuracy. Further training in visual assessment skills is necessary in order to improve the clinicians' estimation.

D-dimers as a screening test for venous thromboembolism in pregnancy: is it of any use?

In non-pregnant women, D-dimers are used successfully to aid diagnosis of suspected pulmonary embolus (PE), as they have high sensitivity, moderate specificity and high negative predictive value. However, D-dimer levels are physiologically raised in pregnancy and thus overlap the values normally associated with PE. The aim of this retrospective study therefore was to investigate the use of D-dimer levels as a screening test for suspected PE in pregnancy and to determine if a negative D-dimer level could exclude the diagnosis in pregnant women. A total of 37 women suspected of PE had both ventilation perfusion (VQ) scans and D-dimer levels performed. Thirteen were reported as having a low probability of PE following VQ scan, while 24 were thought to have a moderate or high probability of PE. Women who had a low probability of PE following VQ scanning were found to have D-dimer levels ranging from 0.25-2.2 mg/l, while women who had a high probability of PE following scanning had D-dimer levels ranging from 0.31-1.74 mg/l. The sensitivity and specificity of D-dimer as a test for suspected PE in pregnancy was calculated to be 0.73 and 0.15 respectively, while the negative likelihood ratio was 1.8. Current guidelines advocate the use of a negative D-dimer result to exclude the diagnosis of PE in pregnancy. However, this study suggests that D-dimer testing in pregnancy has a high negative likelihood ratio and should not be used. Larger prospective observational studies are required to collaborate the findings from this study.

Primary amenorrhoea caused by congenital absence of the uterus.

The authors discuss the case of a 21-year-old female of Afro-Caribbean origin, who presented with primary amenorrhoea, and was found to have congenital absence of the uterus and fallopian tubes in the presence of a normal vaginal cavity.