Free and bound tryptophan in human plasma during the perinatal period.

The concentration of tryptophan and the degree of binding of the amino acid to protein were examined in human plasma during the perinatal period. Both total and unbound (free) tryptophan were higher in cord vein plasma than in the maternal circulation, the concentration gradient being approximately 1 : 2. The proportion of the total plasma tryptophan concentration that was not bound to protein was less in cord vein plasma than in the maternal circulation. After birth the proportion in infant plasma fell significantly. Both total and free tryptophan fell during the first 24 hours of postnatal life. Total tryptophan returned to the cord vein plasma level 6--8 days after birth whilst free tryptophan failed to increase during the period of the observations. In premature infants total and free tryptophan also declined in concentration 12--24 hours after birth, suggesting the phenomenon to be related to birth rather than to gestational age. Phenylalanine remained unchanged whilst tyrosine increased in concentration during the first 80 hours of postnatal life. Thus, the availability of tryptophan to the tissues appears to decline during the immediate postnatal period and the results suggest that the requirement for tryptophan during this time may exceed the supply from standard artifical milk preparations.     

Valproic acid in the perinatal period: decreased maternal serum protein binding results in fetal accumulation and neonatal displacement of the drug and some metabolites

The total concentrations of valproic acid were higher in cord serum than in the serum of epileptic mothers given this drug (fetal/maternal total concentration ratios 1.7 +/- 0.5). The maternal free fractions of VPA correlated with the fetal accumulation of the drug. The fetal/maternal free fraction ratios (0.47 +/- 0.24) correlated inversely with the fetal/maternal total concentration ratios. The free concentrations of VPA in fetal blood were similar to those in maternal blood. These results obtained in vivo were confirmed by an in vitro study in which the drug had been added to drug-free serum samples. The free fractions (x100) of VPA in the maternal serum at birth (27.3 +/- 6.3) were significantly higher than in the serum of adult controls (8.0 +/- 2.4) and in cord serum (11.8 +/- 1.3). The pattern of VPA metabolite binding in the three groups was similar to that of VPA, although an unsaturated metabolite (2-en) was bound to a much higher degree than VPA (greater than 98%). The high total drug load in the fetus was partially displaced from binding sites during the first few postnatal days. The free fractions of the drug and metabolites in the neonates were almost twice as high as those in the fetus at birth. The decreased protein binding of VPA in the mothers at birth and in the neonates during the first postnatal week was related to increased free fatty acid levels. VPA concentrations in mother's milk were much lower than the free concentrations in plasma milk/plasma ratios 0.025 +/- 0.01). In neonates, half-lives for VPA were prolonged (43 +/- 14 hours). Our results indicate that increased free fatty acid concentrations in the maternal blood at the time of birth result in partial displacement of VPA from maternal binding sites, additional placental transfer, and thus fetal accumulation of the drug. The high drug load in the fetus is subsequently partially displaced after birth, resulting in increased free fractions and free concentrations of VPA in the neonate.     

Oxidative stress in preterm neonates at birth and on the seventh day of life

Previous studies have demonstrated increased oxidative damage to proteins and increased lipid peroxidation products in the plasma of hypoxic newborns at birth. We tested the hypothesis that hypoxic preterm newborns are at increased risk for oxidative stress in the first week of life. Heparinized blood samples of 34 hypoxic and 15 control preterm newborns were obtained at birth from the umbilical vein immediately after delivery and from a peripheral vein on postnatal d 7. Plasma levels of hypoxanthine, total hydroperoxide (TH), and advanced oxidation protein products (AOPP) were measured in cord blood and blood drawn on d 7. Hypoxanthine, TH, and AOPP levels were significantly higher in cord and d 7 blood samples of hypoxic newborn than control infants. Statistically significant correlations were observed between AOPP and hypoxanthine and between AOPP and TH plasma levels on d 7. AOPP and TH plasma levels significantly increased from cord to d 7 blood in neonates without hypoxia. These findings show that the oxidative stress observed in cord blood of hypoxic preterm newborns is still higher than control infants on d 7. The significant increase in TH and AOPP levels in nonhypoxic preterm newborns at the end of the first postnatal week indicates that damage caused by free radicals also occurs in nonhypoxic babies with normal clinical course. In summary, TH and AOPP production is prolonged for several days after birth in hypoxic preterm babies. The risk of free radical damage is lower but still exists in preterm neonates with normal clinical course.     

Fetal and Neonatal Cortical Adrenal Function in Birth Asphyxia

ABSTRACT. Eighteen newborn infants, gestational age between 36 and 42 weeks with birth asphyxia were compared with 23 normal newborn infants to determine serum cortisol and dehydroepiandrosterone sulfate levels in cord blood and in venous blood samples collected 12–18 hours after birth. Both groups were similar in gestational age, birthweight, proportion of small for gestational age and large for gestational age infants, proportion of infants delivered by cesarean section with and without labor, and proportion of mothers with pre-eclampsia. There was no antenatal exposure to corticosteroid. The asphyxiated newborn infants had a significantly higher mean cord serum level of cortisol, and a significantly lower mean cord serum level of dehydroepiandrosterone sulfate than the control group. Mean serum cortisol and dehydroepiandrosterone sulfate levels collected 12–18 hours after birth were similar between both groups. It is suggested that elevated cord serum level of cortisol is related to birth asphyxia stress stimulating the adrenal definitive zone, and the low cord serum level of dehydroepiandrosterone sulfate is secondary to a transient hypoxemic-ischemic insult to the adrenal fetal zone.     

Homocysteine, cysteine, and related metabolites in maternal and fetal plasma in preeclampsia

Homocysteine is associated with endothelial dysfunction and cardiovascular disease, and elevated concentrations of homocysteine have been found in preeclampsia. The purpose of this study was to investigate maternal and fetal concentrations of total homocysteine and related metabolites (including cysteine, choline, and betaine), and possible associations with infant birth weight. Women with preeclampsia (n=47) and controls (n=51), who underwent cesarean section, were included. Maternal plasma, umbilical vein, and artery plasma were analyzed. Median concentrations of homocysteine, cysteine, choline, and betaine were significantly higher in women with preeclampsia than controls, both in maternal and fetal plasma. There were no differences in folate and vitamin B12 concentrations between the groups, neither for maternal nor fetal samples. Maternal homocysteine concentration was a negative predictor for birth weight only in the preeclampsia group. Elevated homocysteine and cysteine concentration in maternal circulation in preeclampsia is reflected in the fetal circulation. The clinical significance of elevated homocysteine and cysteine concentrations in maternal and fetal compartments in preeclampsia remain to be explored, both regarding fetal growth and development of disease later in life.     

Postnatal changes in concentrations of free and bound leptin

AIM: To evaluate the effect of maternal diabetes on the concentrations of free and bound leptin at birth and during postnatal adaptation. METHODS: Total, bound, and free leptin concentrations and the percentage of free leptin were measured in cord plasma and plasma at 3 days of age of 13 term infants of mothers with gestational diabetes mellitus (GDM) and 13 term infants of healthy mothers. Gestational age was 40.2 (1.4) weeks, and birth weight was 3693 (549) g (means (SD)). RESULTS: At birth, infants of mothers with GDM had significantly higher concentrations of total, bound, and free leptin and a higher percentage of free leptin (all p < 0.05). In all infants, these concentrations were significantly lower at 3 days of age than at birth (all p < 0.003), and the differences in concentrations of total, bound, and free leptin between the two groups were no longer significant. In infants of mothers with GDM, the percentage of free leptin remained unchanged, and was higher (p<0.05) than in infants of healthy mothers; in the latter group the percentage of free leptin significantly declined (p = 0.02). CONCLUSIONS: GDM appears to influence fetoplacental leptin metabolism. This effect may be mediated through altered maternal glucose metabolism, or insulinaemia, or both.     

II. After Short Gestation and Gestation Complicated by Hypertension with Special Reference to the "Small-for-Dates" Syndrome

In cases of hypertensive disorder there is an increase of urea in the cord vein plasma. The increase seems to be secondary to an occasional increase in the maternal plasma. In cases of hypertensive disorder during pregnancy associated with intrauterine growth retardation of the foetus the ratio between the cord vein plasma levels and the mother's cubital vein plasma levels of essential amino acids is lower than under normal conditions. The low ratios of valine, isoleucine and leucine levels are shown to be due to higher maternal plasma levels at delivery than in normal pregnancies. It is suggested that the findings have some bearing on the growth retardation of the foetus, being the consequence of a diminished supply of essential amino acids to the foetus. The differences from what is found in normal term pregnancies are not due to a shortening of the gestational period, since there is in the foetus, in a gestational period down to 33 weeks, only still higher plasma levels of taurine and lysine. To demonstrate that the material is representative as regards hypertension and the “small-for-dates” syndrome a survey has been made of the weight and length at birth in cases of hypertensive disorder during pregnancy.     

Serum tri-iodothyronine, thyroxine, and thyrotrophin concentrations in newborns during the first 2 days of life.

The serum concentrations of tri-iodothyronine (T3), thyroxine (T4), and thyrotrophin (TSH) were measured in 10 term newborn infants between birth and the age of 2 days by radioimmunoassay. The mean concentration of T3 in maternal serum was 1.62 mug/l, and it increased from the low cord blood level of 0-63 mug/l to the peak value of 1-76 mug/l within the first 2 hours of life. Mean serum T4 concentrations increased from the cord blood level of 145 mug/l to the peak value of 205 mug/l within the first 24 hours of life. The postnatal increase of the mean serum TSH concentrations from the cord blood level of 5-7 mU/l to the peak value of 20-6 mU/l within 2 hours was similar to the increase of T3. These data confirm earlier reports which show that T3 secretion is low at birth and TSH secretion is stimulated strongly but transiently after birth, and that the low T3 secretion is rapidly normalized in 2 hours along with the TSH release. Because of these strong and rapid changes, we recommend screening of the function of the pituitary-thyroid axis in neonates after the age of 24 hours.     

Influence of the maternal plasma glucose concentration at delivery on the risk of hypoglycaemia in infants of insulin-dependent diabetic mothers

Plasma glucose concentrations at birth and at two hours of age were measured in 53 infants of insulin-dependent mothers (IDMs). The plasma glucose concentrations at delivery were measured in the mothers of 17 IDMs and in the remaining 36 mothers, glucose was estimated by interpolation from concentrations achieved just before and after delivery. Clinical and laboratory data from the two groups were otherwise similar, so the groups were combined for further analyses. The maternal plasma glucose at delivery correlated positively with the glucose concentration of the IDMs at birth (rho = 0.82, p less than 0.001) and negatively with the glucose concentration at two hours of age (rho = -0.46, p less than 0.001). Maternal plasma glucose concentration was higher in mothers delivered by caesarean section than in vaginally delivered mothers (p less than 0.05). Eleven IDMs became hypoglycaemic at two hours of life (plasma glucose less than or equal to 1.7 mmol/l). These infants had higher cord plasma glucose concentrations at birth than those who remained normoglycaemic; the maternal glucose concentration was also higher. None of the IDMs became hypoglycaemic if the maternal glucose concentration at delivery was less than 7.1 mmol/l. In 28 IDMs the simultaneous plasma concentrations of non-antibody bound immunoreactive insulin (IRI) were recorded. Cord plasma IRI correlated with glucose and IRI at two hours of age (rho = -0.73, p less than 0.001 and rho = 0.77, p less than 0.001, respectively). Cord plasma IRI was higher in IDMs who became hypoglycaemic than in the remaining infants.(ABSTRACT TRUNCATED AT 250 WORDS)     

ESTIMATION OF FREE THYROXINE INDEX IN THE NEWBORN USING MICRO-METHODS

Abstract. Rogowski, P., Siersbæk-Nielsen, K. and Mølholm Hansen, J. (Medical Department E, the Obstetrical Department, and the Department of Clinical Chemistry, Frederiksberg Hospital, Copenhagen, Denmark). Estimation of free thyroxine index in the newborn using micro-methods. Acta Paediat Scand, 63: 201, 1974.–Thyroid function in the newborn has been studied with the purpose of establishing normal values for total plasma thyroxine, T-3 test and free thyroxine index in the neonatal period using new micro-methods. Total thyroxine determinations were carried out using the Sephadex column method (Tetralute®) which requires 25 to 50 µ1 plasma. The unbound TBG binding sites were evaluatid using a T-3 Sephadex retention test (Trilute®) requiring 50 μl plasma. Free thyroxine index were calculated as the product of the two tests. 202 fullterm newborns were examined in the period 19 to 71 hours after birth and the normal range (95 % limits) for plasma thyroxine were found to be 9.2–26.0 μg/100 ml. Normal values for the T-3 test varied between 42.5 and 64.9 % and free thyroxine index values between 510–1378 arbitrary units. The mean values of total thyroxine, T-3 test and free thyroxine index were found to be significantly increased compared with cord blood and adult mean values indicating a physiological thyroid hyperfunction in the neonatal period. The new thyroid function tests used in the present study were found to be technical simple and are suggested to be used whenever thyroid diseases in the newborn are suspected.     

Birth by cesarean section is associated with elevated neonatal plasma levels of dimethylarginines

Background: This study was undertaken to compare the effects of vaginal delivery and cesarean section on the l‐arginine‐nitric oxide system by measuring levels of l‐arginine, an endogenous nitric oxide synthase antagonist asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA) in the cord blood and postnatally. Methods: Plasma samples were obtained from the umbilical vein and artery at birth and from peripheral venous blood on the second postnatal day in 30 full‐term newborn infants: 10 born vaginally and 20 born by cesarean section. Results: After vaginal delivery, ADMA concentration was higher in the umbilical vein than in the umbilical artery (mean 1.06 vs 0.90 µmol/L [P= 0.027]); and ADMA level fell after birth to 0.66 µmol/L on the second postnatal day (P= 0.007 vs umbilical artery). Newborns born by cesarean section had similar ADMA levels in umbilical arterial and venous blood, 1.19 and 1.18 µmol/L, and the ADMA level fell to 0.84 µmol/L by the second postnatal day (P < 0.001). Vaginal birth induced neither significant umbilical venoarterial difference nor a postnatal fall in SDMA. After cesarean section, SDMA was essentially the same in umbilical vein, umbilical artery and postnatal peripheral vein samples. At 2 days of age, both ADMA and SDMA levels stayed higher in infants born by cesarean section than in vaginally born infants. Conclusions: ADMA level falls after both vaginal and cesarean birth, whereas SDMA level does not. The higher ADMA level after cesarean birth compared with vaginal birth may contribute to decreased nitric oxide production and bioavailability in neonatal vascular beds.     

Influence of the Maternal Plasma Glucose Concentration at Delivery on the Risk of Hypoglycaemia in Infants of Insulin-Dependent Diabetic Mothers

Plasma glucose concentrations at birth and at two hours of age were measured in 53 infants of insulin-dependent mothers (IDMs). The plasma glucose concentrations at delivery were measured in the mothers of 17 IDMs and in the remaining 36 mothers, glucose was estimated by interpolation from concentrations achieved just before and after delivery. Clinical and laboratory data from the two groups were otherwise similar, so the groups were combined for further analyses. The maternal plasma glucose at delivery correlated positively with the glucose concentration of the IDMs at birth (Q=0.82, p <0.001) and negatively with the glucose concentration at two hours of age (Q= -0.46, p <0.001). Maternal plasma glucose concentration was higher in mothers delivered by caesarean section than in vaginally delivered mothers ( p <0.05). Eleven IDMs became hypoglycaemic at two hours of life (plasma glucose ≥1.7 mmol/1). These infants had higher cord plasma glucose concentrations at birth than those who remained normoglycaemic; the maternal glucose concentration was also higher. None of the IDMs became hypoglycaemic if the maternal glucose concentration at delivery was less than 7.1 mmol/l. In 28 IDMs the simultaneous plasma concentrations of non-antibodybound immunoreactive insulin (IRI) were recorded. Cord plasma IRI correlated with glucose and IRI at two hours of age (Q=-0.73, p <0.001 and Q=0.77, p <0.001, respectively). Cord plasma IRI was higher in IDMs who became hypoglycaemic than in the remaining infants. The results suggest that among the factors which may be responsible for neonatal hypoglycaemia in IDMs a major factor may be the maternal plasma glucose concentration at the time of delivery.     

Insulin and glucagon during the perinatal period: secretion and metabolic effects on the liver

Insulin and glucagon are detected in the plasma of most species early in gestation. In the fetus at term, insulin and glucagon secretion can be modified by long-term changes in glucose concentration but the responsiveness of A and B cells to glucose is lower than in the adult. The plasma insulin/glucagon molar ratio is high in the fetus at term, then decreases dramatically immediately after birth and remains low during the first hours of extrauterine life. This situation results in favored hepatic glycogen storage and prevented gluconeogenesis in utero, and sharp glycogen breakdown and active gluconeogenesis during the early postnatal period.     

METABOLIC EVENTS IN INFANTS OF DIABETIC MOTHERS DURING FIRST 24 HOURS AFTER BIRTH III.

ABSTRACT. Plasma amino acid concentrations (AAC) were studied in 31 diabetic mothers (10 of White class A, 10 of B-C and 11 of D-F) and their 32 infants during the first 24 hours after birth. Only minor differences between the 3 groups were found at birth and 2 hours, and none at 12 and 24 hours after birth. The individual AAC in umbilical vein plasma did not correlate with birthweight. All AAC except aspartic acid, aspargine, cystine and glutamic acid were higher in umbilical venous plasma than in maternal plasma. Umbilical venousarterial differences of amino acids did not correlate with maternal or umbilical vein insulin concentrations except for threonine and valine. In general essential amino acids decreased after birth. In 8 infants with hypoglycemia and hyperinsulinism at 2 hours of age several plasma amino acids were lower than in the normoglycemic infants.     

Plasma and urine riboflavin during riboflavin-free nutrition in very-low-birth-weight infants

BACKGROUND: Very-low-birth-weight (VLBW; birth weight <1500 g) infants receive enteral and parenteral nutriture that provides greater daily riboflavin (vitamin B2) than does term infant nutriture, and elevated plasma riboflavin develops in these infants after birth. The purpose of this study was to measure plasma and urine riboflavin concentrations in VLBW infants during riboflavin-free nutrition. Our hypothesis was that elevated plasma riboflavin develops in VLBW infants because of high daily intake and immature renal riboflavin elimination. METHODS: Eighteen clinically healthy VLBW infants received parenteral nutrition and preterm infant formula during the first postnatal month. On postnatal days 10 and 28, the infants received specially prepared riboflavin-free enteral and parenteral nutrition for the 24-hour study period. Serial collections of plasma were made at time 0 and at 12 and 24 hours. Urine was collected continuously for the 24-hour period in 4-hour aliquots. Samples were analyzed for riboflavin concentration. RESULTS: During the 24-hour riboflavin-free study period on postnatal day 10, plasma riboflavin decreased 56% from 185 +/- 37 ng/mL (mean +/- SEM), and urine riboflavin decreased 75% from 3112 +/- 960 mg/mL. Similarly, on postnatal day 28, plasma riboflavin decreased 79% from 184 +/- 32 ng/mL, and urine riboflavin concentration decreased 91% from 5092 +/- 743 ng/mL during the 24-hour riboflavin-free study period. Riboflavin half-life (t(1/2)) was 18.5 hours on postnatal day 10 and decreased 48% by postnatal day 28. Riboflavin elimination was 145.1 +/- 20.6 mg/kg per day on postnatal day 10 and increased 40% by postnatal day 28. CONCLUSION: The VLBW infants who received parenteral nutrition and preterm infant formula had elevated plasma riboflavin on postnatal days 10 and 28. Plasma riboflavin t(1,2) was shorter and renal riboflavin elimination was greater on postnatal day 28 than on postnatal day 10. Plasma riboflavin was normal after 24 hours of riboflavin-free nutrition. The pattern of plasma and urine riboflavin in VLBW infants suggests a lower daily intake would maintain plasma riboflavin close to normal.     

Oxidative stress and antioxidant status in fetal circulation in preeclampsia

Preeclampsia is associated with oxidative stress in maternal circulation. The purpose of this study was to explore oxidative stress and antioxidants in the fetal circulation in preeclampsia. Women with preeclampsia (n = 19) or uncomplicated pregnancies (n = 33) delivered by cesarean section were included. Blood was sampled separately from the umbilical vein and artery. 8-Iso-prostaglandin F(2alpha) (8-isoprostane), a stable product of lipid peroxidation, is a reliable marker of oxidative stress. Concentration of total 8-isoprostane in cord plasma was analyzed by gas chromatography-mass spectrometry. Antioxidant status was evaluated measuring ferric reducing ability of plasma and vitamin E. There was no difference between preeclampsia and control groups regarding median plasma concentration of 8-isoprostane in umbilical vein (955 versus 780 pg/mL, p = 0.41) or in umbilical artery (233 versus 276 pg/mL, p = 0.65). Concentration of 8-isoprostane was much higher in plasma from the umbilical vein than artery, suggesting placenta as the source of 8-isoprostane. Median ferric reducing ability of plasma concentration was higher in preeclampsia than in controls, both in the umbilical vein and artery. Median vitamin E concentration in the umbilical vein was higher in preeclampsia, but no difference was found in the umbilical artery. In conclusion, no evidence of increased oxidative stress, evaluated by 8-isoprostane concentration, was found in fetal circulation in preeclampsia.     

Which mothers wean their babies prematurely from full breastfeeding? An Australian cohort study

Aim:  To identify the maternal and infant characteristics associated with an early transition from full breastfeeding to complementary or no breastfeeding during the first 2 months of life in a large, representative cohort of Australian infants.
Method:  Multinomial logistic modelling was performed on data for infants with complete breastfeeding and sociodemographic data (N = 4679) including maternal age, education, smoking, employment, pregnancy and birth outcomes.
Results:  Ninety-one percent of women initiated breastfeeding. Sixty-nine percent of infants were being fully breastfed at 1 month, and 59% were fully breastfed at 2 months. Maternal characteristics – age less than 25 years, smoking in pregnancy, early full-time postnatal employment and less educational attainment – were associated with early breastfeeding cessation. Infant factors – multiple birth, caesarean birth, infant or first birth – were associated with a transition to complementary breastfeeding in the first postnatal month.
Conclusion:  Breastfeeding duration is substantially affected by breastfeeding outcomes in the first postpartum month. The first month is an important window for evidence-based interventions to improve rates of full breastfeeding in groups of women identified as at risk of early breastfeeding cessation.     

LIPIDS IN CORD SERUM AND FREE FATTY ACIDS IN PLASMA IN HEALTHY NEWBORN TERM INFANTS

ABSTRACT. Christensen, N. Chr. (Department of Obstetrics, Odense University Hospital, Odense, Denmark). Lipids in cord serum and free fatty acids in plasma in healthy newborn term infants. Acta Paediatr Scand, 63: 711, 1974.—Serum cholesterol, triglycerides, and glycerol in cord serum and plasma FFA in cord blood and at 1 1/2, 6, 12, 24 and 48 hours after birth were determined in 18 healthy term infants. Concentrations of lipids in cord blood were low; and there were no correlation between cord lipids and subsequent FFA values. A rapid increase in FFA level, with peak values at 12 hours, was seen. Significant, negative correlations were found between FFA concentration and rectal temperature at 1 1/2 hour and between total caloric intake and FFA concentration at 48 hours.     

Characteristics of tryptophan binding in the serum of the newborn rat.

During the very first period of postnatal life, tryptophan is almost entirely free in the serum of rats. This situation is in sharp contrast with the well-known ability of serum albumin to bind the essential amino acid in the adult. Three main factors accounted for the relative lack of binding during the early postnatal life when compared to the adult: (1) the lower concentration of serum albumin, the binding protein; (2) the inhibition of binding by nonesterified fatty acids, which were at a high level in the serum of young rats until weaning, and (3) the decreased number of available binding sites for tryptophan on the defatted serum albimin, whereas the apparent association constant of tryptophan binding to serum albumin was similar in newborn and adult. Since immunological characterization of newborn and adult serum albumins did not reveal a specific fetal serum albumin, we suggest that discrete changes at the association site for tryptophan are sufficient to induce large alteration in the binding capacity of the protein. In contrast to the situation observed in adult rats, serotonin synthesis in the brain of newborn animals is therefore not dependent on the equilibrium between bound and free tryptophan in serum.     

Trace elements in the serum of mothers and their children.

The serum copper, zinc and iron levels, iron binding capacity and coeruloplasmin activity were determined in 28 maternal and cord bloods and in 50 infants and children. At the end of the gestation period the serum copper level increased, iron concentration remained unchanged while the level of zinc decreased significantly as compared to the values for healthy, non-pregnant women. Iron and zinc concentrations at birth were significantly higher in the newborn than in the mother, whereas the copper level amounted only to 20% of the maternal value. Subsequently, the copper level increased to reach the lower limit of healthy adults in the first to second year of life. The remarkably high neonatal zinc concentration fell significantly in the first 2 to 4 weeks of life and decreases to the normal adult level at one year of age. The changes in the trace element concentrations may be due to quantitative differences in the transporting proteins, variations in placental permeability and in the function of transfer proteins.