Anatomical and functional changes of the fetal adrenal gland in intrauterine growth restriction.

OBJECTIVE: The aim of this study was to demonstrate the establishment of adrenal sparing in intrauterine growth restricted (IUGR) human fetuses. IUGR fetuses are a subgroup of small for gestational age (SGA) fetuses that are unable to reach their own growth potential because of chronic hypoxia and undernutrition. We hypothesized that in IUGR fetuses the adrenal gland is relatively larger and secretion of noradrenaline (NA), adrenaline (A), and cortisol is increased. STUDY DESIGN: This is a prospective observational study including 65 singleton pregnancies (42 IUGR and 23 controls). Using two-dimensional ultrasound, we measured fetal adrenal diameters and adrenal/abdominal circumference (AD/AC) ratio between 25 and 37 weeks. We considered only one measurement per fetus. In 21 pregnancies we also measured NA, A, and cortisol levels in arterial and venous fetal cord blood collected at the time of delivery. RESULTS: The AD/AC ratio was significantly higher in IUGR fetuses than in controls. Cord NA and A levels were significantly higher in IUGR fetuses than in controls. An increase in cortisol secretion in IUGR fetuses was observed but the difference was not statistically significant. CONCLUSIONS: Adrenal sparing correlates with a relative increase in adrenal measurements and function.

Thymic volume in healthy, small for gestational age and growth restricted fetuses.

OBJECTIVE: The aim of this study was to verify the hypothesis that a difference in thymic size exists between small for gestational age (SGA) fetuses, likely constitutional, and intrauterine growth restricted (IUGR) fetuses because of placental causes. METHODS: We studied 27 SGA and 36 control fetuses. SGA was defined as fetal abdominal circumference (AC) and birthweight <10th percentile for gestational age. We defined as constitutional SGA those with normal uterine and umbilical artery Doppler flow velocity waveforms (FVW), and as IUGR those with abnormal uterine FVW. IUGR were further divided based on normal or abnormal umbilical FVW. Fetal thymic volume (TV) was acquired by three-dimensional ultrasound and reconstructed with virtual organ computer-aided analysis. To correct for the influence of fetal size on thymic dimension, TV/AC ratio was calculated. RESULTS: Controls presented a higher TV/AC compared with each group of SGA (p < 0.001). TV/AC was significantly lower in IUGR with abnormal umbilical FVW compared with both constitutional SGA (p = 0.01) and IUGR with normal umbilical FVW (p = 0.01). CONCLUSIONS: The differences in TV/AC between constitutional SGA and IUGR with abnormal umbilical FVW suggest that, in the latter, a specific 'trigger' might compromise trophoblastic invasion and thymic development; however, some kind of alteration of the immune system might occur in all SGA fetuses.