Circulating beta-2-microglobulin levels during pregnancy and their possible relationship with feto-maternal histocompatibility

Quantification of Fetal Renal Function Using Fetal Urine Production Rate and Its Reflection on the Amniotic and Fetal Creatinine Levels During Pregnancy

Adequate prediction of fetal exposure of drugs excreted by the kidney requires the incorporation of time-varying renal function parameters into a pharmacokinetic model. Published data on measurements of fetal urinary production rate (FUPR) and creatinine at various gestational ages were collected and integrated for prediction of the fetal glomerular filtration rate (GFR). The predicted GFR values were then compared to neonatal values recorded at birth. Collected data for FUPR across different gestational ages using both 3D (N = 517) and 2D (N = 845) ultrasound methods showed that 2D techniques yield significantly lower estimates of FUPR than 3D (p < 0.0001). A power law function was shown to best capture the change in FUPR with fetal age (FA) for both 2D ( F U P R 2 D ( m L min ) = 0 . 000169     FA 2 . 19 ); and 3D ( F U P R 3 D   ( m L min ) =   3 . 21 × 1 0 - 7   FA 4 . 21 ) data. The predicted FUPR based on the observed 3D data was shown to be strongly linearly related (R ² = 0.95) to measured values of amniotic creatinine concentration (N = 664). The FUPR_3D data together with creatinine levels in the fetal urine and serum resulted in median predicted fetal GFR values of 0.47, 1.2, 2.5, and 4.9 ml/min at 23, 28, 33, and 38 weeks of fetal age (50% CV), respectively. These values are in good agreement with neonatal values observed immediately at birth. The derived FUPR and creatinine functions can be utilized to assess fetal renal maturation and predict fetal renal clearance.

Associations between maternal and fetal serum levels of immune activation markers and fetal growth

During pregnancy, signs of maternal immunologic sensitization to fetal HLA and other fetoplacental alloantigens are often detectable in peripheral blood. Presumbly, this in part reflects immune activity at the maternal-fetal interface. This response may involve activation of maternal T cells, which stimulate placental growth via lymphokine production. To shed light on this mechanism, data on placental weight, neonatal anthropometry, gestational age, fetomaternal HLA relationships (reflecting a potential for HLA allosensitization), and serum levels of three immune activation markers in maternal and cord blood were collected in a sample of 61 primiparous women and their neonates. The activation markers were soluble CD8 antigen (sCD8), interleukin-2 receptor (sIL-2R), and beta-2 microglobulin (β₂ m). Mean fetal and maternal sCD8 and β₂ m levels, and mean fetal sIL-2R levels were significantly higher than published norms. Fetal means for all three markers exceeded maternal means, and both sIL-2R and β₂ m were highly correlated between mother and fetus. This suggests that fetal sIL-2R and β₂ m levels result in part from transport or diffusion from the maternal compartment. No associations were found between fetomaternal HLA relationships, activation markers, and placental weight. The difference between the fetal and maternal β₂ m value was significantly correlated with birth weight, controlling for chest circumference and crown-heel length. Associations between birth weight and fetomaternal HLA relationships could not be interpreted with certainty. These findings suggest that maternal immune activation and diffusion or transport of β₂ m into fetal compartment enhances fetal growth in fat-free body mass. © 1995 Wiley-Liss, Inc.