Prenatal 2D Ultrasound reveals significant adrenal gland adaptation in patients with Fetal growth restriction: Study
Fetal growth restriction (FGR) is defined as a pathological in utero growth disorder primarily caused by factors related to the fetus, the mother, or the placenta. Neonatal mortality rates are higher in FGR compared to cases in which there is normal growth. Additionally, FGR is associated with increased risks of both short- and long-term neonatal morbidities, such as intraventricular hemorrhage, infections, respiratory distress, delayed brain development, impaired endocrine function, and cardiovascular disease.
The principal cause of placenta-related FGR is insufficient remodeling of the uterine spiral arteries that supply the placenta. The maintenance of blood supply to vital organs such as the brain, myocardium, and adrenal glands requires redistribution of fetal circulation, primarily through the hypothalamus-pituitary-adrenal axis (HPA). Glucocorticoid (GC) hormones, particularly cortisol, are crucial in managing stress responses during fetal development and in regulating the growth and maturation of fetal tissues and organs.
The fetal adrenal glands, appearing early at 28–30 days post fertilization, are among the largest organs when the fetus is near term. The fetal adrenal cortex undergoes rapid growth during the prenatal period and divides into three zones: the fetal zone (FZ), the definitive zone (DZ), and the transitional zone (TZ). The fetal adrenal medulla, however, is not recognizable until delivery. The FZ is responsible for the synthesis of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S), which are crucial for facilitating placental estrogen production. Meanwhile, the DZ and TZ, also known as the “neocortex,” are involved in the production of cortisol and aldosterone during pregnancy.
The fetal adrenal glands comprise a highly vascularized organ, which receives blood from several primary arteries: the superior adrenal artery (SAA), middle adrenal artery (MAA), and inferior adrenal artery (IAA), which originate from the inferior phrenic artery, abdominal aorta, and renal artery, respectively. The superior and inferior portions of the DZ are primarily supplied by the SAA and IAA, respectively, while the FZ is predominantly supplied by the MAA.
Theoretically, chronic fetal hypoxia and stress could trigger the activation of the HPA axis, potentially affecting both the adrenal vessels and the adrenal glands. Therefore, a study was carried out to compare the differences in Doppler indices of the adrenal artery and adrenal gland sizes between fetuses with growth restriction and those with normal growth.
This study aimed at comparing the Doppler indices of the adrenal artery and the adrenal gland sizes between FGR and those with normal growth. A multicenter, cross-sectional study was conducted from February to December 2023. Authors compared 34 FGR to 34 with normal growth in terms of inferior adrenal artery (IAA) Doppler indices and adrenal gland volumes.
The IAA peak systolic velocity (PSV) in the FGR group was 14.9±2.9 cm/s compared to 13.5±2.0 cm/s in the normal group, with a mean difference of 1.4 cm/s (p value = 0.017). There were no significant differences between groups in terms of IAA pulsatility index (PI), resistance index (RI), or systolic/diastolic (S/D), with p values of 0.438, 0.441, and 0.658, respectively. The volumes of the corrected whole adrenal gland and the corrected neocortex were significantly larger in the FGR group, with p values of 0.031 and 0.020, respectively.
The Doppler study of the IAA in fetuses with growth restriction revealed a significant increase in PSV, while no changes were observed in the PI, RI, and S/D compared to those with normal growth. Additionally, both the corrected WAG volume and the corrected neocortex volume were significantly enlarged in FGR.
Both increased IAA PSV and enlarged volumes of the corrected WAG and neocortex were found in fetuses with FGR, suggesting significant adrenal gland adaptation in response to chronic intrauterine stress.
Source: Suphawan et al; Wiley Journal of Pregnancy Volume 2024, Article ID 9968509, 10 pages https://doi.org/10.1155/2024/9968509
Both increased inferior adrenal artery peak systolic velocity and enlarged volumes of the corrected whole adrenal gland volume and neocortex were found in fetuses with suggesting significant adrenal gland adaptation in response to chronic intrauterine stress.
