Appropriate For Gestational Age Fetuses Research Articles

Effect of fetal growth restriction on ultrasonographically measured cardiac size

The effect of fetal growth restriction on cardiac size is controversial. It has not been established whether cardiac size of small for gestational age (SGA) fetuses is smaller or larger than appropriate for gestational age (AGA) fetuses. Such controversy may stem from heterogeneity in study population in previous reports. Both fetal hypoxemia and increased impedance to flow in fetoplacental vessels, two findings often encountered in severe fetal growth restriction, may lead to cardiomegaly. Therefore we have measured cardiac dimensions and cardiothoracic indices in a homogeneous group of SGA fetuses without ultrasonographic or Doppler evidence of fetal distress or increased umbilical artery flow impedance (n = 10). This group was compared with AGA fetuses matched for sex and estimated fetal weight (n = 20). No differences were observed between the two groups in cardiac and chest measurements and indices. Heart circumference and area significantly correlated with fetal weight, both among AGA (r = 0.88 for both; P < 0.0001), as well as SGA fetuses (r = 0.89 and 0.88, respectively; P = 0.0006 and 0.0008).

Atrial natriuretic peptide levels in fetal blood in relation to inferior vena cava velocity waveforms

To determine whether blood levels of atrial natriuretic peptide in small for gestational age (SGA) fetuses are related to Doppler indices measured in arterial and venous vessels. Atrial natriuretic peptide was assayed in fetal blood obtained at funipuncture in 42 third-trimester fetuses, of whom 11 were appropriate for gestational age (AGA) and 31 were SGA. Small for gestational age fetuses were divided into three groups according to Doppler findings in the umbilical artery and inferior vena cava: 1) normal in both vessels (n = 10); 2) abnormal in the umbilical artery but normal in the inferior vena cava (n = 10); and 3) abnormal in both vessels (n = 11). Atrial natriuretic peptide levels were related to Doppler indices and acid-base status of the fetal blood. Small for gestational age fetuses with abnormal waveforms in both vessels had higher atrial natriuretic peptide blood levels (median 544.8 pg/mL, range 404.2-1112.3) compared with AGA fetuses (median 316.8 pg/mL, range 159.3-470.1; P < or = .001), SGA fetuses with normal waveforms only in both vessels (median 299.8 pg/mL, range 242.6-480.5; P < or = .001), and SGA fetuses with abnormal waveforms only in the umbilical artery (median 367.6 pg/mL, range 192.7-748.9; P = .002). Blood levels of atrial natriuretic peptide were significantly related to the preload index in the inferior vena cava (p = 0.554, P < or = .001). This relation remained significant when the analysis was restricted to the SGA fetuses with abnormal waveforms in the umbilical artery and the inferior vena cava (p = 0.673, P = .03). Small for gestational age fetuses with abnormal velocity waveforms in the inferior vena cava have significantly higher concentrations of atrial natriuretic peptide. This may represent a compensatory mechanism in the SGA fetus for regulation of an abnormal hemodynamic condition.

Fetal redistribution of blood flow and amniotic fluid volume in growth-retarded fetuses.

Our purpose was to assess the relationship between the fetal redistribution of blood flow and the amount of amniotic fluid in appropriate-for gestational-age fetuses and growth-retarded fetuses. Blood flow velocity waveforms of the umbilical artery, descending aorta, middle cerebral artery, renal artery and uterine artery were recorded using pulsed Doppler ultrasonography in 100 appropriate-for gestational age fetuses and 39 growth-retarded fetuses. The pulsatility index (PI) values and the amount of amniotic fluid were compared between the two groups. The PI values of the umbilical artery and renal artery were significantly higher in appropriate for gestational-age-fetuses with oligohydraminos than in fetuses with an adequate amount of amniotic fluid. The PI values of the umbilical artery and renal artery were significantly higher and the PI of the middle cerebral artery was significantly lower in growth-retarded fetuses with oligohydramnios than in fetuses with an adequate amount of amniotic fluid. Furthermore, there was a significant negative correlation between the PI value of the renal artery and the vertical diameter of amniotic fluid, and between the PI value of the renal artery and the amniotic fluid index. The PI value of the renal artery was related to the amount of amniotic fluid in growth-retarded fetuses, and the same relationship was demonstrated in appropriate-for gestational age fetuses.

Cerebellar doppler velocimetry in the appropriate- and small-for-gestational-age fetus

To compare superior cerebellar artery flow velocity waveforms in the appropriate-for-gestational-age (AGA) and the small-for-gestational-age (SGA) fetus. Superior cerebellar artery velocity waveforms were obtained prospectively from 172 AGA fetuses at 17-41 weeks' gestation. The pulsatility index (PI) was used to quantify the waveforms. Superior cerebellar artery velocity waveforms were also obtained from 30 SGA fetuses divided into group A (n = 15), with a normal umbilical artery PI, and group B (n = 15), with an abnormal umbilical artery PI. The transverse cerebellar diameter was measured in all SGA fetuses. The superior cerebellar artery PI was best represented by a second-order polynomial equation [PI = 0.145 + 0.101 x (gestational age) - 0.00197 (gestational age)2]. Small-for-gestational-age fetuses of group A had a superior cerebellar artery PI in the normal range, whereas 13 of 15 fetuses of group B (86.7%) had a PI value less than the individual 95% confidence interval. The transverse cerebellar diameter in group A fetuses was in the normal range in ten of 15 cases, whereas it was in the normal range for all group B fetuses. Small-for-gestational-age fetuses with an abnormal umbilical artery PI have "cerebellar-sparing effect," as suggested by a superior cerebellar artery PI less than the normal range and a normal transverse cerebellar diameter.

Third trimester fetal growth and umbilical venous blood concentrations of IGF-1, IGFBP-1, and growth hormone at term.

Insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-1 (IGFBP-1) and growth hormone (GH) concentrations were measured in umbilical venous blood after delivery of 78 term newborn infants. Three groups of pregnancies were prospectively identified during the third trimester, according to fetal size and subsequent fetal growth, assessed by repeated ultrasound scans. Fetal size was considered either appropriate for gestational age (AGA) or small for gestational age (SGA), according to whether the first ultrasound measurement of abdominal circumference was equal to or above, or below the tenth centile for gestational age, respectively. Subsequent fetal growth was quantified by the change in the standard deviation score of abdominal circumference measurements between the first and last scans before delivery. Fetal growth retardation (FGR) was defined as a (negative) change in SD score of greater than -1.5. Eighteen SGA fetuses with evidence of FGR had significantly lower IGF-1 (median 0.05 (range 0.0-0.24) U/ml) at delivery than 35 SGA fetuses with normal growth (median 0.13 (range 0.0-0.94) U/ml; P < 0.05) and 25 AGA fetuses with normal growth (median 0.31 (range 0.0-0.84) U/ml; P < 0.05). The median concentration in the SGA group with normal growth was also significantly lower than that of the AGA group with normal growth. There were no significant differences in IGFBP-1 or GH concentrations between the three groups. These observations indicate that umbilical blood concentrations at birth of IGF-1, but not IGFBP-1 or GH, relate to both fetal size and fetal growth during the third trimester of pregnancies reaching term.

Fetal Blood Sampling From Intrahepatic Vein Versus Cord Insertion: Effect on pH and Blood Gases

To determine whether venous pH, base excess, and blood gas values collected by antenatal ultrasound-guided sampling from the fetal intrahepatic vein (intra-abdominal umbilical vein, portal sinus, or portal vein) differ from those obtained from the placental cord insertion. Retrospective analysis was done of 1053 clinically indicated fetal blood sampling procedures performed between 1988-1992. One hundred sixty-eight appropriate for gestational age (AGA) singleton fetuses were identified after exclusion of those with conditions believed likely to have impaired fetal blood gas status. Fetal venous pH, carbon dioxide pressure, oxygen pressure, and base excess from 52 samplings at the intrahepatic vein were compared cross-sectionally to those from 116 samplings at the placental cord insertion, using analysis of covariance to correct for gestational age. There was no systematic difference in the blood gas or acid-base values between the two sites of fetal venous blood sampling. Acid-base and blood gas status in AGA fetuses is not affected by the site of sampling. Values obtained at the intrahepatic vein may be interpreted using reference ranges derived from sampling at the placental cord insertion.

Fetal Blood Sampling From Intrahepatic Vein Versus Cord Insertion: Effect on pH and Blood Gases

Objective: To determine whether venous pH, base excess, and blood gas values collected by antenatal ultrasoundguided sampling from the fetal intrahepatic vein (intraabdominal umbilical vein, portal sinus, or portal vein) differ from those obtained from the placental cord insertion. Methods: Retrospective analysis was done of 1053 clinically indicated fetal blood sampling procedures performed between 1988-1992. One hundred sixty-eight appropriate for gestational age (AGA) singleton fetuses were identified after exclusion of those with conditions believed likely to have impaired fetal blood gas status. Fetal venous pH, carbon dioxide pressure, oxygen pressure, and base excess from 52 samplings at the intrahepatic vein were compared crosssectionally to those from 116 samplings at the placental cord insertion, using analysis of covariance to correct for gestational age. Results: There was no systematic difference in the blood gas or acid-base values between the two sites of fetal venous blood sampling. Conclusions: Acid-base and blood gas status in AGA fetuses is not affected by the site of sampling. Values obtained at the intrahepatic vein may be interpreted using reference ranges derived from sampling at the placental cord insertion.(Obstet Gynecol 1993;82:504-8)

Glucose gradients of maternal vein-umbilical vein and umbilical vein-umbilical artery in normally grown and growth-retarded fetuses

The present study was designed to investigate the roles of maternal-fetal glucose transport and fetal glucose utilization in the regulation of fetal growth. Maternal venous blood, umbilical arterial and venous blood were sampled simultaneously in 60 full-term appropriate-for gestational age (AGA) fetuses and 48 small-for-gestational-age (SGA) fetuses. The cases were divided into four groups: group 1 consisted of 35 AGA fetuses, group 2 consisted of 25 AGA fetuses, group 3 consisted of 25 SGA fetuses, and group 4 consisted of 22 SGA fetuses. The mothers of group 1 and 3 were given 2.5% glucose in 0.9% normal saline and those of groups 2 and 4 by cesarean section received normal saline or Ringer's lactate at least one hour prior to delivery of the fetus SGA fetuses were found to have hypoglycaemia of umbilical venous blood, increased (maternal vein-umbilical vein) MV-UV and decreased UV-UA (umbilical vein-umbilical artery) glucose gradients, all of which disappeared after maternal glucose supplementation. However, hypoinsulinemia and lower insulin/glucose ratio in SGA fetuses persisted either with or without maternal parenteral glucose infusion. Increased MV-UV and decreased UV-UA glucose gradients suggests placental dysfunction and poor glucose utilization in SGA fetuses. The lower fetal insulin/glucose ratio may imply pancreatic dysfunction in SGA fetuses, which did not respond to glucose challenge from the maternal side. It seems that in SGA fetuses, placental dysfunction interferes with maternal-fetal transfer with resulting fetal hypoglycemia; on the other hand, pancreatic dysfunction leads to poor glucose utilization and retarded intrauterine growth. However, the mechanism that primarily accounts for pancreatic dysfunction in these fetuses remains to be resolved.

Doppler echocardiographic assessment of time to peak velocity in the aorta and pulmonary artery of small for gestational age fetuses

The time to peak velocity was measured at the level of the ascending aorta and pulmonary artery by Doppler echocardiography in 38 small-for-gestational age (SGA) fetuses before and during maternal hyperoxygenation. The values were compared to a reference range derived from the study of 142 appropriate-for-gestational age (AGA) fetuses. In the SGA fetuses the time to peak velocity at the level of pulmonary artery was significantly lower and at the level of the aorta significantly higher than in AGA fetuses. During maternal hyperoxygenation the aortic time to peak velocity decreased towards normal range but there was no significant change at the level of the pulmonary artery. These results may indicate variations of aortic and pulmonary pressures in SGA fetuses that can be partially modified by maternal hyperoxygenation and which may be associated with changes in the peripheral resistance of the cerebral circulation.

Plasma cortisol and adrenocorticotropin in appropriate and small for gestational age fetuses.

Plasma cortisol and adrenocorticotropin (ACTH) were measured in fetal blood samples obtained by cordocentesis from 61 appropriate for gestational age (AGA) and in 41 small for gestational age (SGA) fetuses at 18-38 weeks gestation. Fetal plasma cortisol (mean 74 nmol/l) did not change but plasma ACTH increased between 18 and 36 weeks gestation and the two were not significantly correlated. Plasma cortisol in cord blood samples after vaginal delivery at term (mean 305 nmol/l) was higher than in samples at elective cesarean section (mean 151 nmol/l), and there was a significant correlation between fetal and maternal levels. The findings suggest that in human fetuses a late gestational rise in plasma cortisol may not be necessary for organ maturation and that the high fetal plasma cortisol in spontaneous labor at term is probably the result rather than the cause of labor. In SGA fetuses, plasma cortisol was higher and ACTH lower than in AGA fetuses, and plasma cortisol was inversely correlated to fetal hypoglycemia, suggesting that in the chronically hypoglycemic SGA fetus the fetal pituitary is under negative inhibition.