Cord prealbumin values in newborn infants: effect of prenatal steroids, pulmonary maturity, and size for dates

Umbilical Cord and Neonatal Transthyretin and Their Relationship to Growth and Nutrition in Preterm Infants

BACKGROUND

Transthyretin (TTR), also known as prealbumin, has been suggested as an indicator of protein and nutritional status.

OBJECTIVE

The aim of this study was to examine the maternal and umbilical cord (UC) TTR in relation to intrauterine growth, and the serum TTR of preterm infants in relation to nutritional status and growth.

METHODS

After application of exclusion criteria, 49 preterm infants (mean gestational age and birth-weight 32.9±2.9 weeks and 1822±556 g) were included in the study. Transthyretin was sampled at birth and on days 14, 28, and at discharge with growth parameters and nutritional laboratory test results.

RESULTS

Mean UC and maternal TTR were positively correlated (8.5±2.4 mg/dL and 20.4±7.0 mg/dL, r=0.31, P=0.07). Umbilical cord TTR was neither an index of maturity nor of intrauterine growth. Umbilical cord TTR was higher in females (9.4±2.6 versus 7.6±1.8 mg/dL, P=0.015). Maternal TTR was lower in twin pregnancies (16.8±4.9 versus 22.5±7.3 mg/dL, P=0.007). Although TTR levels gradually increased over time in correlation with post-menstrual and chronological ages (r=0.24, P=0.011 and r=0.40, P<0.001, respectively), there was no correlation to weight gain (r=0.10, P=0.41), nutritional status, protein intake, or nutritional laboratory test results. The only significant correlations were between TTR and glucose and triglycerides levels (r=0.51, P<0.001 for both).

CONCLUSIONS

Although TTR levels increased over time, we could not demonstrate significant correlations between TTR and indices of the nutritional status in preterm infants at birth or during the neonatal course.

Transthyretin levels are not related to Apgar score in low birth weight and very low birth weight infants

BACKGROUND

Previous studies have reported an increased incidence of thyroid dysfunction in premature/low birth weight infants. The cord blood concentrations of transthyretin (TTR), a thyroid hormone binding protein, have also been found to be decreased in preterm infants. While thyroid hormone concentrations are decreased in sick infants, it is not known if physical condition influences TTR levels. Serial concentrations of TTR following birth have not previously been reported.

AIMS

To measure serial serum concentrations of TTR in premature infants following birth, and determine whether TTR levels are related to physical condition.

METHODS

A cohort of 65 premature very low birth weight (VLBW) and LBW infants were studied. Serum samples were obtained on the day of birth, and for 8 weeks following birth. Apgar scores at birth as well as the incidence of respiratory distress syndrome (RDS) were noted.

RESULTS

Baseline serum T4 concentrations and Apgar scores were significantly lower in VLBW infants, while the severity of RDS was significantly higher in the VLBW group. Multivariate analyses revealed that T4 levels were negatively associated with RDS, while TSH concentrations were positively related to gestational age. TTR concentrations were not related to gestational age at birth, Apgar score, or RDS, and did not change markedly over 8 weeks.

CONCLUSIONS

These findings suggest that serum TTR concentrations are not related to birth weight/gestational age and are not associated with either clinical condition at birth (as assessed by Apgar score) or the occurrence of RDS. Reference values for TTR concentrations in VLBW and LBW infants are provided from birth to 8 weeks of age.

Reference range for micronutrients and nutritional marker proteins in cord blood of neonates appropriated for gestational ages

BACKGROUND

Reference values of numerous micronutrients at different gestational ages (GA) have not been yet reported based on large series.

AIMS

This study aimed to establish the reference range for zinc, copper, selenium, vitamin A, vitamin E, retinol binding protein, transthyretin, albumin, transferrin and ceruloplasmin in neonates and to give the profiles according to gestational age.

STUDY DESIGN

A total of 510 infants appropriate for gestational age were included in the study. The determinations were done using the serum cord blood of 262 term and 248 preterm infants (gestational age of 37 to 42 and 26 to 36 weeks, respectively).

RESULTS

All nutrients correlated significantly with birth weight and gestational age but different patterns were highlighted. Vitamin A, retinol binding protein and prealbumin showed a triphasic pattern with a cut-off at about 36 to 39 weeks. In this period, these parameters rised significantly (P<0.001). Albumin and selenium showed a biphasic pattern with a significant positive correlation (P<0.001) between weeks 26 to 38. Transferrin and ceruloplasmin associated with copper showed a continuous increase with GA (P<0.001). On the opposite, zinc and vitamin E decreased. Zinc showed a biphasic pattern with a significant negative correlation (P<0.001) between the 26th to 34th weeks. Vitamin E presented a triphasic pattern with a cut-off at about 32 to 35 weeks (P<0.001).

CONCLUSION

The large number of data allow the build-up of reference ranges and charts for the evaluation of micronutrients and proteins in high-risk neonates.

Nutritional assessment and therapeutic interventions for the preterm infant

All components of assessment contribute to the final decision regarding nutritional status of the infant and the nutritional therapy indicated. One parameter by itself such as nutrient intake, weight change, or a laboratory value cannot clearly determine the total nutritional state of the infant. Achieving appropriate intakes and weight gains are two excellent parameters. Laboratory values can determine if nutrition is tolerated and manipulations are indicated.

Low thyroxinaemia occurs in the majority of very preterm newborns

Transient hypothyroxinaemia with normal thyroid stimulating hormone (TSH) levels is a well-known condition in preterm neonates and is generally assumed to be a harmless epiphenomenon of prematurity. This assumption is, however, based on studies that included very few neonates with a gestational age (GA) below 30 weeks. We therefore measured serum free thyroxine (FT4) and serum TSH on days 1 and 14 in 263 neonates with a GA between 26 and 41 weeks. In 13 infants (5%), transient hypothyroidism (low FT4 and TSH >20 mU/l on day 14) was found. In the remaining 250 patients FT4 on days 1 and 14 but not TSH correlated positively with GA. In neonates with a GA of 35-41 weeks, FT4 increased postnatally to levels within or above the normal adult range. In contrast, in the very preterm group (26-31 weeks) the already low FT4 levels declined to values significantly below the range observed in term neonates. A significant proportion of these neonates had FT4 levels within the hypothyroid range. There was no difference in thyroid function between neonates treated with povidone-iodine or chlorhexidine.

CONCLUSION

Very preterm neonates have FT4 levels on day 14 that are much lower than is generally assumed while TSH remains in the normal range. We therefore propose to measure FT4 in all preterms with a GA below 33 weeks, during the 2nd week of life.

Concentration of twelve plasma proteins at birth in very low birthweight and in term infants

Plasma samples obtained at birth from 70 very low birth weight (VLBW) infants (gestational age 24 to 34 weeks) and from 20 term infants were analysed for concentrations of 12 different proteins. The plasma concentrations of albumin, transthyretin (TTR), retinol-binding protein (RBP), vitamin D-binding protein, apolipoprotein A I, fibronectin, orosomucoid and alpha 1-antichymotrypsin were significantly lower in the VLBW infants than in the term infants, whereas the values of alpha-fetoprotein (AFP) were significantly higher in the VLBW infants. No differences were found between the two groups for apolipoprotein A II, apolipoprotein B and transferrin. Birth asphyxia and sex had no influence on the measured plasma protein concentrations. The plasma concentrations of apolipoprotein A I and A II were significantly lower in small-for-gestational age (SGA), VLBW infants compared with appropriate-for-gestational age (AGA), VLBW infants. Possible acute inflammation (defined as raised concentrations of orosomucoid or alpha 1-antichymotrypsin) was associated with significantly higher values of vitamin D-binding protein in both VLBW and term infants, suggesting that this protein may act as an acute phase protein in newborn infants.

Maturation of thyroid function in normal human foetuses

The functional maturation of an independent foetal thyroid activity was investigated in the present study. Serum concentrations of total T4, free T4, TSH and TBG were measured in 23 foetuses between 18 and 31 weeks' gestational age. Foetal samples were collected by transabdominal needling from the placental cord insertion. TT4, FT4, TBG and TSH levels significantly increased with gestational age. FT4 levels were comparable with the adult range by 28 weeks' gestation; TBG levels reached adult values at approximately 30 weeks, while TT4 was lower than adult levels throughout the whole period studied. TSH values were, in all cases, higher than the normal adult range. A significant positive correlation was present between TT4 and TBG, TT4 and TSH, and TBG and TSH levels; on the contrary, no correlation was demonstrated between FT4 and TSH levels. The TSH/TT4 ratio significantly decreased with gestational age. The results suggest an incomplete responsiveness of the foetal thyroid gland to TSH, while the feedback control system between pituitary and thyroid is operating at a different set point from that in post-natal life. The normal range of thyroid parameters established is of clinical relevance for the antenatal diagnosis, and eventual treatment of thyroid disorders that may seriously damage foetal development and maturation.

A comparison of the mid-arm circumference/head circumference ratio and ponderal index for the evaluation of newborn infants after abnormal intrauterine growth

We studied the accuracy of the ponderal index and the mid-arm circumference/head circumference ratio for detecting newborn infants who were likely to be symptomatic because of aberrant intrauterine growth. Sixty infants were evaluated because of suspected intrauterine growth retardation; both the mean ponderal index and mid-arm circumference/head circumference ratio were significantly lower in the group of 30 symptomatic infants than in the group of 30 asymptomatic infants (p less than 0.05). However, the mid-arm circumference/head circumference ratio identified a significantly higher percentage of the symptomatic infants than the ponderal index (80% vs. 47%; p = 0.007). An additional 60 infants were evaluated because of suspected abnormal intrauterine growth acceleration. The mean mid-arm circumference/head circumference ratio, but not the ponderal index, was significantly higher in the group of 30 symptomatic infants than in the group of 30 asymptomatic infants (p less than 0.005). Again, the mid-arm circumference/head circumference ratio identified a significantly higher percentage of the symptomatic infants than the ponderal index (79% vs. 33%; p less than 0.001). The mid-arm circumference/head circumference ratio is more accurate than the ponderal index for the evaluation of potentially symptomatic newborn infants who suffered abnormal fetal growth. The ponderal index is not useful for the detection of symptomatic large-for-dates infants.

Cord transferrin and ferritin values in newborn infants at risk for prenatal uteroplacental insufficiency and chronic hypoxia

We measured cord transferrin and ferritin levels in 50 newborn infants with fetal conditions associated with either uteroplacental vascular insufficiency or chronic hypoxia. Sixteen small for gestational age infants, 21 infants of mothers with preeclampsia, and 13 symptomatic infants of diabetic mothers had significantly higher transferrin levels and lower ferritin levels and calculated iron stores than did asymptomatic gestational age-matched control infants without these conditions. Cord ferritin levels and calculated iron stores were significantly lower in the infants of diabetic mothers than in any other group of infants. Cord transferrin levels were inversely correlated with ferritin levels (r = -0.59, P less than 0.001) and were unrelated to transthyretin levels and birth weight in the high-risk infants, but were positively correlated with ferritin levels (r = 0.50, P less than 0.001), transthyretin levels (r = 0.65, P less than 0.001), and birth weight (r = 0.75, P less than 0.001) in the control infants. We conclude that cord transferrin levels do not reflect protein-energy status in newborn infants with prenatal histories suggesting uteroplacental insufficiency or chronic hypoxia, and that when associated with decreased cord ferritin levels, indicate possible impaired iron stores in these infants.