Intima-media thickness measurements in the fetus and mother during pregnancy: a feasibility study.

Fetal intima-media thickness (IMT) has been suggested as a marker of pre-clinical atherosclerosis, and maternal IMT could be altered through dynamic circumstances related to pregnancy. We investigated the feasibility of measurement of IMT at four pre-defined fetal and four pre-defined maternal arterial locations to determine vascular changes that could be associated with impaired vascular function. IMT was measured from the first to third trimester (12-34 wk), in 38 low-risk pregnancies. We imaged a 10-mm region of interest using a Mindray (Shenzhen, China) high-resolution ultrasound machine with automated IMT measurement software. Fetal abdominal aorta IMT was measurable during the second trimester in 71% and during the third trimester in 100% of the case, and umbilical artery IMT was measurable in 50% and 82% of cases during the second and third trimesters, respectively. Fetal IMT measurements were not possible during the first trimester. It was not often feasible to measure the IMT of the fetal common carotid artery, fetal renal artery and maternal iliac artery (maximal 20% of cases). Maternal common carotid artery, abdominal aorta and uterine artery IMTs were measurable throughout pregnancy. There was a significant relation between gestational age and IMT in the umbilical artery (p = 0.03) and a significant relation between body mass index and IMT in the maternal common carotid artery (p = 0.01). IMT measurements are feasible in some maternal and fetal vessels of interest. Further studies are underway to obtain more insight into vascular development during normal and pathologic pregnancies.

Neonatal morbidity in growth-discordant monochorionic twins: comparison between the larger and the smaller twin.

Fetal growth restriction in singletons has been shown to enhance fetal lung maturation and reduce the risk of respiratory distress syndrome due to increased endogenous steroid production. However, data on lung maturation in growth-discordant monochorionic (thus, identical) twins are lacking. Our objective was to compare the risk of severe neonatal morbidity between the larger and the smaller twin in monochorionic twins with birth weight discordance (BWD). We included in the study all consecutive monochorionic diamniotic pregnancies with severe BWD (≥25%) and two live-born twins delivered at our center (n=47 twin pairs). We compared the incidence of neonatal morbidity, particularly respiratory distress syndrome (RDS), and cerebral lesions between the larger and the smaller co-twin. The incidence of severe neonatal morbidity in the larger and smaller twin was 38% (18/47) and 19% (9/47), respectively (odds ratio (OR) 2.66, 95% confidence interval (CI) 0.94-7.44) and was due primarily to the higher incidence of RDS, 32% (15/47) and 6% (3/47), respectively (OR 6.88, 95% CI 1.66-32.83). In conclusion, this study shows that the larger twin in monochorionic twin pairs with BWD is at increased risk of severe neonatal morbidity, particularly RDS, compared to the smaller twin.

Arterio-venous flow between monochorionic twins determined during intra-uterine transfusion. Nonlinear decay of adult red blood cells.

Recently, we derived equations relating the flow of adult red blood cells through a placental arterio-venous anastomosis with intra-uterine and post-natal measured adult hemoglobin concentrations. In this letter, we re-derived the equations, now including a more realistic nonlinear decay of adult red blood cells, and re-evaluated the measurement accuracy of the arterio-venous flow and the lifetime of the red blood cells.

Bilirubin/albumin ratios in fetal blood and in amniotic fluid in rhesus immunization.

OBJECTIVE: To test the hypothesis that unconjugated bilirubin is equally distributed over the albumin molecules present in fetal blood and amniotic fluid in Rhesus (Rh) immunization. METHODS: Molar concentrations of unconjugated bilirubin and albumin were measured in fetal blood and amniotic fluid samples, obtained before the first intrauterine transfusion in 30 nonhydropic, anti-D-alloimmunized fetuses, with gestational ages ranging from 20 to 35 weeks. RESULTS: Bilirubin concentration in amniotic fluid was best predicted by a combination of bilirubin concentration in fetal blood (P<.001), albumin concentration in fetal blood (P=.008), and albumin concentration in amniotic fluid (P<.001) (adjusted R2=0.91). The bilirubin/albumin ratios in fetal blood were linearly correlated with the bilirubin/albumin ratios in amniotic fluid (R2=0.75, P<.001). However, the bilirubin/albumin ratios in fetal blood were always higher than the bilirubin/albumin ratios in amniotic fluid (regression coefficient 1.4, 95% confidence interval 1.1-1.7). In our population, a bilirubin/albumin ratio in amniotic fluid of 0.10 or greater had a better sensitivity and specificity to predict severe anemia (Z hemoglobin -5 standard deviations or less) than the Queenan 4 or the Liley 2c line. CONCLUSION: The relation between fetal hemolysis and amniotic fluid bilirubin concentration is based on the linear correlation between bilirubin/albumin ratios in fetal blood and in amniotic fluid. The slope in Queenan's and Liley's chart follows that of the albumin concentration in amniotic fluid during gestation. LEVEL OF EVIDENCE: III.

Arterio-venous flow between monochorionic twins determined during intra-uterine transfusion.

Twin-twin transfusion syndrome (TTTS) is a severe complication of monozygotic (identical) twin fetuses sharing one single (monochorionic) placenta. TTTS is caused by a net inter-twin transfusion of blood through placental anastomoses, from one twin (the donor) to the other (the recipient), which link the two feto-placental circulations. Currently, the only reliable method to measure the net inter-twin transfusion clinically is when incomplete laser therapy of TTTS occurs and one of the twins becomes anemic and requires an intra-uterine transfusion of adult red blood cells. Then, differences between adult hemoglobin concentrations measured during the transfusion and at birth relate not only to the net inter-twin transfusion but also to the finite lifetime of the adult red blood cells. We have analyzed this situation, derived the differential equations of adult hemoglobin in the donor and recipient twins, given the solutions and given expressions relating the net inter-twin flow with clinically measured parameters. We have included single and multiple intra-uterine transfusions. In conclusion, because incomplete laser therapy occurs frequently, and some cases require an intra-uterine transfusion, this method may allow collecting a wealth of net inter-twin flow data from clinicians involved in laser therapy of TTTS. To aid to the widespread use of this method, we have presented the equations as clearly as possible in tables for easy use by others.

Hypoalbuminemia: a cause of fetal hydrops?

OBJECTIVE: The pathophysiology of fetal hydrops is still unclear. One factor that is believed to contribute to hydrops is hypoalbuminemia. Our research question was whether hypoalbuminemia in immune hydrops is causative or a secondary effect. STUDY DESIGN: Between 1987 and 2005, fetal blood samples were taken at the first fetal blood transfusion in 224 Rh-D alloimmunized pregnancies. We measured hemoglobin concentration and albumin concentration and assessed the severity of hydrops. RESULTS: A decrease in albumin concentration occurred only below a hemoglobin deficit of >8 SDs in 27 fetuses. In 161 nonhydropic, 44 mildly hydropic, and 19 severely hydropic fetuses, albumin concentrations were >2 SDs below the mean for gestational age in 6%, 14%, and 63%, respectively. CONCLUSION: Our finding that most fetuses with immune hydrops have an albumin concentration within the normal range (71%) suggests that hypoalbuminemia is unlikely to cause the initial development of immune hydrops.