Fetal adrenal artery velocimetry measurements in appropriate-for-gestational age and intrauterine growth-restricted fetuses

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.

The Impact of Fetal Growth Restriction on Prenatal 2D Ultrasound and Doppler Study of the Fetal Adrenal Gland

Background: Uteroplacental insufficiency in fetuses with growth restriction (FGR) leads to chronic hypoxia and stress, predominantly affecting the adrenal glands. However, the mechanisms of impact remain unclear. Objectives: This study is aimed at comparing the Doppler indices of the adrenal artery and the adrenal gland sizes between FGR and those with normal growth. Materials and Methods: A multicenter, cross-sectional study was conducted from February to December 2023. We compared 34 FGR to 34 with normal growth in terms of inferior adrenal artery (IAA) Doppler indices and adrenal gland volumes. Results: 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 (95% confidence interval [CI]: 0.27-2.65; 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. Conclusion: Both increased IAA PSV and enlarged volumes of the corrected whole adrenal gland and neocortex were found in fetuses with FGR, suggesting significant adrenal gland adaptation in response to chronic intrauterine stress.

Color Doppler ultrasound in high-low risk pregnancies and its relationship to fetal outcomes: a cross-sectional study

Objective

To calculate the multivessel color Doppler indices in high-risk and low-risk pregnancies and relate these to fetal outcomes.

Methods

The investigation involved 60 patients who were pregnant. The patients were separated into groups according to assessment of low and high risk. The patients underwent color Doppler ultrasonography to detect the maternal and fetal blood vessels, and the measured Doppler indices were then analyzed for any association with fetal outcomes.

Results

The gestational stages (in weeks) of the participants at the respective times of investigation and delivery were 32.06 ± 2.98 and 36.2 ± 1.78 in the low-risk group and 29.21 ± 1.95 and 29.83 ± 1.86 in the high-risk group. The pulsatility index (PI), resistive index (RI), and systolic/diastolic ratio (SD) decreased with gestation length in the low-risk group, whereas in the high-risk group, these values increased in the uterine and umbilical arteries. With increased gestational stage, MCA-PSV (peak systolic velocity) in the middle cerebral artery (MCA) increased, while PI decreased. Pulsatile and reversal flow of the uterine vein, the vein of Galen, and the umbilical vein were noted in high-risk pregnancies, and these negatively affected the fetal outcome. The fetal venous parameters were more specific and sensitive for predicting an unfavorable fetal outcome than the arterial factors, with a greater negative predictive value.

Conclusion

The results of our study indicate that abnormal Doppler indices of the blood vessels in high-risk pregnant patients will result in adverse clinical outcomes. Therefore, the patients can be monitored and managed accordingly using Doppler ultrasonography.

Evaluation of fetal adrenal artery Doppler velocimetry and fetal adrenal gland size in pregnancies after recovery from COVID-19

AIM

Assessment of the fetal adrenal gland (FAG) size and middle adrenal artery (MAA) Doppler parameters in pregnancy recovered from Coronavirus Disease (COVID-19) and comparison of the values with the healthy control group.

METHODS

Thirty-eight pregnant women who had recovered from COVID-19 infection and 76 healthy control group between 33 and 35 weeks of gestation were involved in this case-control study. Fetuses were examined for fetal biometry, fetal well-being, adrenal gland dimensions, and Doppler parameters 4-6 weeks after the diagnosis of COVID 19 infection. FAG dimensions were measured in two planes and MAA blood flow velocity was evaluated with pulsed Doppler. Pregnant women with COVID-19 infection were grouped according to the National Institutes of Health for the severity of the disease, and those with mild and moderate infections were examined in the study.

RESULTS

The total adrenal gland (TAG) height, fetal zone (FZ) length and width, and MAA-Peak Systolic Velocity (MAA-PSV) were significantly higher, and the MAA-Pulsatility Index (MAA-PI) was significantly lower in the COVID-19 group (p < 0.05). The lower in MAA-PI and the higher in MAA-PSV, the width of the FZ, and width of the TAG were found to be significant in the moderate group compared to the mild groups (p < 0.05).

CONCLUSION

COVID-19 pregnancies might cause early maturation of the FAG and its vasculature depends on the intrauterine stress due to the hyper-inflammation, so fetuses exposed to maternal COVID-19 suggested to have an increase in blood flow to the adrenal gland and fetal adrenal size.

Evaluation of fetal middle adrenal artery Doppler and fetal adrenal gland size in pregnancies with fetal growth restriction: a case-control study

OBJECTIVES

This study aims to evaluate sonographic measurements of fetal adrenal gland size and middle adrenal artery Doppler in pregnancies with fetal growth restriction (FGR) and in a healthy control group.

METHODS

This prospective study included 107 singleton pregnancies with FGR between 24 and 42 weeks of gestation and 107 pregnancies with fetuses whose growth was appropriate for gestational age (AGA). Adrenal gland size and Doppler parameters of the adrenal artery were measured and the values and obstetric outcomes were compared between the study and control groups.

RESULTS

In the study group, the Z-scores of total adrenal width-length and height, fetal zone width-length and middle adrenal artery-peak systolic velocity (MAA-PSV) were significantly higher than those in the control group (p<0.05). The Z-scores of middle adrenal artery-pulsatility index (MAA-PI) were significantly lower in the study group than in the control group (p<0.05). The rate of neonatal intensive care unit admission in fetuses with high adrenal artery PI scores was higher in the FGR group (p<0.05).

CONCLUSIONS

In the present study, we observed decreased adrenal artery PI, increased adrenal blood flow, and increased fetal adrenal volume in fetuses diagnosed with fetal growth restriction, most likely in response to placental insufficiency and chronic hypoxia.

The thrifty phenotype hypothesis: The association between ultrasound and Doppler studies in fetal growth restriction and the development of adult disease

Barker pioneered the idea that the epidemic of coronary heart disease in Western countries in the 20th century, which paradoxically coincided with improved standards of living and nutrition, has its origin in fetal life. Indeed, there is substantial evidence associating low birthweight because of fetal growth restriction with an increased risk of vascular disease in later adult life. These conclusions led to the second part of the Barker hypothesis, the thrifty phenotype, in which adaptation to undernutrition in fetal life leads to permanent metabolic and endocrine changes. Such changes are beneficial if the undernutrition persists after birth but may predispose the individual to obesity and impaired glucose tolerance if conditions improve. The hypothesis assumes that a poor nutrient supply during a critical period of in utero life may "program" a permanent structural or functional change in the fetus, thereby altering the distribution of cell types, gene expression, or both. The fetus, in response to placental undernutrition and to maintain sufficient vascular supply to the brain, decreases resistance to blood flow in the middle cerebral artery. Simultaneously, because of the limited blood supply to the fetus, the arterial redistribution process is accompanied by increased resistance to flow to other fetal vital organs, such as the heart, kidneys, liver, and pancreas. It may explain why individuals exposed to ischemic changes in utero develop dyslipidemia, lower nephron number, and impaired glucose tolerance, all factors contributing to metabolic syndrome later in life. Nevertheless, support for the hypotheses comes mainly from studies in rodents and retrospective epidemiologic studies. This review focused on ultrasound and Doppler studies of human fetal growth restriction in several fetal organs: the placenta, fetal circulation, brain, heart, kidneys, adrenal glands, liver, and pancreas. Support for the hypothesis was provided by animal studies involving conditions that create fetuses with growth restriction with effects on various fetal organs and by human studies that correlate impaired fetal circulation with the in utero development and function of fetal organs.

Zone-specific reference ranges of fetal adrenal artery Doppler indices: a longitudinal study

Background

The fetal adrenal gland is a highly vascularized organs and develops two recognizable distinct zones in uetro, inner fetal zone (FZ) and outer definitive zone (DZ). Based on the region supplied, middle adrenal artery (MAA) mainly contribute to FZ while inferior adrenal artery (IAA) mainly to the inferior part of DZ. The purpose of this study was to establish reference ranges of adrenal artery Doppler indices of IAA and MAA, and assess zonal difference of blood supply to fetal adrenal gland.

Methods

The pulsatility index (PI), resistance index (RI), and systolic:diastolic ratio (S/D) of the IAA and MAA were obtained serially at 4-week intervals in normal fetuses. The MAA and IAA were referred based on the course and location in the gland: IAA referring the artery that mainly branches from the renal artery and walks along the renal upper pole, distributing the inferoposterior part of DZ in the adrenal gland while MAA as arterial blood flowing along the single central adrenal vein in the medial part of the gland. Multilevel modeling was performed to establish the gestational age-associated reference ranges for IAA and MAA. Differences in Doppler indices between the IAA and MAA were assessed.

Results

One hundred sixty-eight fetuses with 843 observations were included. The IAA had a higher detection rate than the MAA (100% vs 89.2%, p < 0.05). The resistance of IAA had a reduction around 35 weeks of gestation and that of MAA remained unchanged throughout the second half of pregnancy. Lower PI, RI and S/D were observed in the MAA than in the IAA (p < 0.05) from 752 paired measurements.

Conclusion

There is a zonal difference in blood supply in favor of the fetal zone, which may correspond to its unique function. Reference ranges of Doppler parameters in adrenal artery maybe beneficial for further evaluation of fetal hemodynamics.

Inferior Adrenal Artery PI in Fetuses with IUGR: Value Indicating Early Blood Redistribution and Steroidogenic Response

OBJECTIVE

To characterize the inferior adrenal artery (IAA) pulsatility index (PI) in intrauterine growth-restricted (IUGR) fetuses without brain sparing.

METHODS

Twenty-three IUGR fetuses with a normal Doppler cerebroplacental ratio (CPR) and 23 normal controls were included in this prospective cross-sectional study. The PI of the IAA was recorded using routine transabdominal Doppler ultrasound. The differences in Doppler characteristics, perinatal outcomes, and steroidogenesis in the umbilical vein at birth (adrenocorticotropic hormone [ACTH] and cortisol [F] levels) were compared between the 2 groups. The correlations between IAA-PI and steroidogenesis were assessed in the IUGR group.

RESULTS

IAA-PI was significantly lower in IUGR fetuses than in normal controls (0.85 vs 1.18 at first scan, 0.78 vs 0.92 at last scan; both P < 0.001). The plasma F and ACTH levels in IUGR cases were significantly higher than those of the normal controls (18.2 vs 12.4 µg/dL and 280.5 vs 125.6 pg/mL for F and ACTH, respectively; both P < 0.001). There were negative correlations between IAA-PI and plasma F values and between IAA-PI and ACTH values in the IUGR group (r = -0.774 and -0.82 at first scan, r = -0.525 and -0.45 at last scan, respectively; P < 0.001).

CONCLUSION

Increased adrenal gland blood flow with concomitant increases in ACTH and F levels were observed in IUGR fetuses. IAA-PI is useful to assess early blood redistribution and may be beneficial for evaluating the steroidogenic response in high-risk pregnancies.

Ultrasound measurement of fetal adrenal gland in fetuses with intrauterine growth restriction, an early predictive method for adverse outcomes

OBJECTIVES

Comparing the sonographic measurements of fetal adrenal gland in pregnancies with intrauterine growth restriction (IUGR) versus healthy controls and to assess whether the changes in adrenal gland measurements could predict adverse pregnancy outcomes in IUGR fetuses.

METHODS

This prospective cohort study evaluated 97 pregnant women (48 with IUGR pregnancies and 49 healthy controls) during their third gestational trimester. All mothers underwent two dimensional ultrasonography of the fetal adrenal gland, and the fetal zone in transverse, sagittal, and coronal planes. Adrenal gland volume (AGV) and fetal zone volume (FZV) were calculated and corrected (c) for fetal weight. The mothers were then followed until delivery.

RESULTS

Fetuses in the IUGR group had larger corrected adrenal gland volume (c_AGV) and smaller corrected fetal zone volume (c_FZV) compared to the fetuses in the control groups (p < .001). In the IUGR group, significantly smaller c_AGV and higher fetal/adrenal were detected in IUGR fetuses who had nonreassuring fetal status before delivery, preterm birth, very low birth weight delivery, and also those who required neonatal intensive care unit admission (p < .01 for all).

CONCLUSIONS

Third trimester fetal adrenal gland sonography could potentially be used as an easy noninvasive method for identifying those IUGR fetuses who might have poorer outcomes.

Bowel circulation in normally grown and growth-restricted fetuses

OBJECTIVES

The purpose of this study was to characterize bowel blood flow and its relationship with cerebral and placental circulations in normally grown and growth-restricted fetuses.

METHODS

In a cross-sectional prospective study of singleton normally grown fetuses, Doppler blood flow pulsatility indices were measured in the superior mesenteric artery, middle cerebral artery, and umbilical artery from 19 to 38 weeks' gestation. The same Doppler parameters were examined in intrauterine growth-restricted (IUGR) fetuses and analyzed as two groups: (1) without a brain-sparing effect, defined as an umbilical artery/middle cerebral artery ratio of less than 1; and (2) with a brain-sparing effect, defined as an umbilical artery/middle cerebral artery ratio of greater than 1.

RESULTS

A total of 262 appropriate-for-gestational-age fetuses were analyzed for superior mesenteric artery Doppler pulsatility index values; 196 were simultaneously examined for umbilical artery and middle cerebral artery pulsatility index values. Forty-three IUGR fetuses were similarly analyzed. In appropriate-for-gestational-age fetuses, both the bowel and brain circulations showed a globally higher pulsatility index as pregnancy advanced, resulting in an almost constant middle cerebral artery/superior mesenteric artery ratio (r(2) = 0.079). The IUGR fetuses had a lower superior mesenteric artery pulsatility index compared to the appropriate-for-gestational-age fetuses, which was more pronounced in those with brain sparing (group 2) than in group 1 (Z = -0.97 and -0.53, respectively; P < .0001). The middle cerebral artery/superior mesenteric artery ratio was higher with respect to the appropriate-for-gestational-age fetuses in group 1, whereas the ratio in group 2 was lower (Z = 0.16 and -0.60).

CONCLUSIONS

We have shown the existence of a superior mesenteric artery sparing effect in IUGR fetuses. This reaction seems to correlate positively with the severity of the growth restriction.

Obstetric management of intrauterine growth restriction

The aim of obstetric management is to identify growth-restricted foetuses at risk of severe intrauterine hypoxia, to monitor their health and to deliver when the adverse outcome is imminent. After 30-32 gestational weeks, a Doppler finding of absent or reverse end-diastolic flow in the umbilical artery of a small-for-gestational age foetus is in itself an indication for delivery. In very preterm foetuses, the intrauterine risks have to be balanced against the risk of prematurity. All available diagnostic information (e.g., Doppler velocimetry of umbilical artery, foetal central arteries and veins and of maternal uterine arteries; foetal heart rate with computerised analysis of short-term variability; amniotic fluid amount; and foetal gestational age-related weight) should be collected to support the timing of delivery. If possible, the delivery should optimally take place before the onset of late signs of foetal hypoxia (pathological foetal heart rate pattern, severely abnormal ductus venosus blood velocity waveform, pulsations in the umbilical vein).

Fetal growth restriction due to placental disease

Normal fetal growth depends on the genetically predetermined growth potential and its modulation by the health of the fetus, placenta and the mother. Fetuses that are small because of intrauterine growth restriction (IUGR) are at higher risk for poor perinatal and long-term outcome than those who are appropriately grown. Of the many potential underlying processes that may result in IUGR, placental disease is clinically the most relevant. Fetal cardiovascular and behavioral responses to placental insufficiency and the metabolic status are interrelated. The concurrent evaluation of fetal biometry, amniotic fluid volume, heart rate patterns, arterial and venous Doppler, and biophysical variables therefore allow the most comprehensive fetal evaluation in IUGR. In the absence of successful intrauterine therapy, the timing of delivery is perhaps the most critical aspect of the antenatal management. A discussion of the fetal responses to placental insufficiency and a management protocol that accounts for multiple Doppler and biophysical parameters as well as gestational age is provided in this review.

Intrauterine growth restriction

Pathophysiological processes underlying intrauterine growth restriction are very complex and poorly understood. Growth restricted fetuses are at risk of hypoxia and, therefore, an early diagnosis of intrauterine growth restriction is important for initiation of fetal surveillance. Application of a three-dimensional ultrasound method for estimation of fetal weight promises better precision. Use of conditional standard deviation scores of fetal biometric variables has been suggested for improved individualized evaluation of intrauterine growth. Application of umbilical artery Doppler velocimetry in the clinical management of growth-restricted fetuses after 32 weeks of gestation leads to decreased perinatal mortality and lower rates of obstetric interventions. Evaluation of fetal state before 32 weeks is difficult and should include Doppler examination of placental circulation and several fetal arterial and venous vessel beds. In addition, recordings of short-term variability of fetal heart rate and biophysical profile have been suggested for fetal surveillance. Important new data on the time sequence of Doppler changes in various vessels of compromised very preterm growth restricted fetuses have been presented, which will enable the establishment of clinical management protocols for evaluation in prospective randomized studies.

Doppler velocimetry in the adrenal artery in human fetuses

BACKGROUND

Fetal hypoxia and/or acidosis causes redistribution of blood flow to the high-priority organs including the adrenal glands. Although this phenomenon is well described in the human cerebral and placental circulations using Doppler velocimetry, there are few reports about the adrenal glands.

AIM

To clarify the gestational age-related changes in adrenal blood flow in normal fetuses and fetuses at risk of hemodynamic derangement.

MATERIAL AND METHODS

In 153 normal cases, the resistance indices (RIs) calculated from the blood flow velocity waveforms (FVWs) in the middle adrenal artery (MAA) were obtained from 24 weeks to construct nomogram using regression analysis. Twenty-seven complicated cases were divided according to the 5%ile RI values in the MAA, and clinical outcomes were retrospectively compared.

RESULT

The RI values in the MAA increased until 31 weeks and decreased thereafter. The 50%ile regression curve was represented as RI=-0.000914 (weeks)(2)+0.0579 weeks-0.181. Of the 27 complicated cases, 13 had RIs in the MAA below the 5%ile. Cases with low RI had significantly higher RI ratio in regard of UA/MCA; higher occurrence of abnormal FHR patterns on observation; higher incidence of cesarean delivery for nonreassuring fetal well-being status; earlier gestational age at delivery; lower birth weights and longer periods of admission to NICU than the cases with normal RI.

CONCLUSION

We have described the nomogram for the RI in the MAA. In conditions of fetal hypoxia or acidemia, blood flow redistribution to the adrenal glands may occur and the analysis of the adrenal artery FVWs may be useful in detection of fetal altered hemodynamics.