Acta Pædiatrica ISSN 0803-5253
REGULAR ARTICLE
Body composition in late preterm infants in the first 10 days of life and at full term Elisabeth Olhager ([email protected]), Caroline T€ornqvist €ping, Sweden Division of Paediatrics, Department of Clinical and Experimental Medicine, Faculty of Health Science, Linkoping University, Linko
Keywords Air displacement plethysmography, Body composition, Fat mass, Fat-free mass, Preterm infants Correspondence E Olhager, Department of Neonatology, Skane University Hospital, SE-221 85 Lund, Sweden. Tel: +46 46 178286 | Email: [email protected] Received 29 September 2013; revised 1 February 2014; accepted 10 March 2014. DOI:10.1111/apa.12632
ABSTRACT Aim: To investigate changes in body weight, fat-free mass, fat mass and percentage of body fat during early life and at full-term postconceptional age (PCA) in preterm infants born after 32 gestational weeks and before 37. Methods: Twenty-nine late preterm infants underwent growth and body composition assessment by air displacement plethysmography (ADP) at the age of 4 days and at fullterm PCA. In 25 of these infants, body composition was assessed three times between days four and nine of life. The preterm infants were compared with 29 full-term infants, matched for gestational age, sex and body weight. Results: There was a significant increase in birth weight and fat-free mass between days four and nine of life. Preterm infants had significantly more body fat 382 180 g vs 287 160 g than full-term infants at full-term PCA. Preterm infants showed poor linear growth between birth and full-term PCA. Conclusion: Weight gain after the initial postnatal weight loss consists of gain in fat-free mass. At full-term PCA, preterm infants were stunted. When compared with full-term new born infants matched for body weight and gestational age, preterm infants had more body fat and a higher percentage of body fat.
INTRODUCTION Preterm infants often experience early postnatal growth failure, which is already evident at full-term postconceptional age (PCA) and may be associated with a negative long-term neurological outcome (1). Aggressive nutritional management has been proposed to minimize later developmental delays, the goal being to achieve a postnatal weight gain approximately equal to foetal growth rates (2). However, rapid weight gain in early infancy has been associated with increased risks of obesity and metabolic syndrome later in life (3). Furthermore, it has been shown that children who are born prematurely have an isolated reduction in insulin sensitivity, which may be a risk factor for type 2 diabetes mellitus (4). In recent years, there has been increasing focus on the quality of growth in preterm infants (5,6). Studies comparing the body composition of preterm infants at full-term PCA with that of full-term newborns show preterm infants are not only shorter and lighter, but they also have more body fat and less fat-free mass (7). This is alarming, because this pattern of growth may correlate with impaired cognitive outcome (1,5). Most studies of the body composition of preterm infants have been carried out in infants born before 32 gestational weeks (1,6,7). A study of late preterm Italian infants born after gestational week 32, but before 37 completed gestational weeks, found rapid catch-up growth in fat mass between birth and one-month old (8,9). In Sweden, this group of infants represents 3–4% of all newborns and, in
fact, almost 25% of infants admitted to neonatal units, making them by far the largest patient group (10). Although these late preterm infants are relatively healthy compared with infants born before 32 completed gestational weeks, they have higher mortality and morbidity than full-term newborn infants (10). The period around birth is very important, as the first days of postnatal life are a time of enormous change (11). Several studies have highlighted the high-fat content in preterm infants at full-term PCA, but little attention has been paid to their body composition development during the first postnatal days (12). One study reported data on the body composition of preterm and full-term infants within 48 h of birth, stating that the proportion of body fat in late
Key notes
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 737–743
Conflicting data exist regarding early and late changes in body composition in late preterm infants. We found that weight gain after the initial postnatal weight loss consisted of gain in fat-free mass and preterm infants (n = 29) had a higher percentage of body fat than full-term infants (n = 29). This pattern of growth and body composition development may be associated with increased risks of obesity and the metabolic syndrome in later life.
737
€rnqvist Olhager and To
Body composition in late preterm infants
preterm infants, assessed by dual-energy X-ray absorptiometry (DEXA), was as high as 13–14% (13). In 2004, equipment based on the air displacement plethysmography (ADP) technique became available, enabling accurate, quick and noninvasive assessment of body composition in infants weighing between one and eight kilograms (9,14,15). This technique has subsequently been used to measure the body composition of full-term and preterm infants. It is well accepted by parents, healthcare staff and infants and is therefore well suited for clinical studies. We used the ADP technique in a group of late preterm infants to study changes in body composition during the early postnatal period. Our first aim was to describe changes in body weight, fat mass and fat-free mass in such infants during the first 10 days of life. Our second aim was to compare their body composition at full-term PCA with corresponding values for full-term new born infants matched for PCA, sex and weight.
MATERIALS AND METHODS Study design Body weight, fat-free mass and fat mass were assessed in 29 preterm infants (Group One). The infants were examined on day four one of life, on two additional occasions during the first 10 days of life and at full-term PCA. Four infants were not assessed on the following two occasions. Values obtained at full-term PCA were compared with those for 29 full-term newborn infants (Group Two). For this comparison, infants were matched for sex, body weight (100 g) and PCA (3 days). Infants in Group Two were examined on day six two of life. Figure 1 shows the infants who participated in the study. Preterm infants Between February 2008 and June 2009, 166 preterm infants, born after at least 32 gestational weeks, were € ping admitted to the neonatal intensive care unit at Linko
Group 1 n = 29 preterm infants, investigated on day four of life
Four preterm infants were not eligable for investigations on day 6 and 9 of life.
Group 1 n = 29 preterm infants investigated att full-term post conceptional age
Group 2 n = 29 full-term infants
Figure 1 Flow diagram of the infants who participated in the study.
738
University Hospital. Gestational age was based on the date of the last menstrual period and ultrasound in gestational week 11–12. Postconceptional age was calculated using chronological age plus gestational age. Forty-one of these infants met the following criteria: birth weight over 1500 grams, singletons, weight and length appropriate for gestational age according to Swedish growth reference values (16), no need for respiratory support (ventilator, continued airway pressure or extra oxygen), no need for parenteral nutrition and no sepsis or malformation. Parents were asked for permission for their child to participate in the study, and permission was granted for 30 infants (29 infants had valid results). These infants were all fed according to current practice at the neonatal unit, which includes special efforts to initiate and maintain maternal lactation. As most preterm infants are unable to suck effectively, breast milk was initially fed through a nasogastric tube. If the mother was unable to provide breast milk, the infants were fed formula (Pepti Junior, Mead Johnsson). On day four of life, nine infants received formula, 13 received formula plus their mother’s breast milk, and seven only received their mother’s breast milk. At full-term PCA, two infants were fed formula, four were fed formula plus breast milk, and 23 only received breast milk. Feeding regimes were not recorded between discharge from the unit and the day of assessment. Full-term infants Twenty-nine healthy full-term newborn infants were € ping University recruited from the maternity ward at Linko Hospital. Fourteen had participated in a previous study (17). The infants were fed according to the guidelines of the maternity unit, where all mothers are encouraged to breastfeed. At the time of investigation, two infants were formula fed, two received formula plus breast milk and 25 were completely breastfed. Anthropometry at birth In the delivery room, all infants were weighed without clothing on an electronic baby scale (Tanita Corporation, Tokyo, Japan) and their length measured by means of a measuring board. Head circumference was measured with a plastic measuring band. Body composition Body composition was assessed using an ADP system (Pea Pod, Cosmed USA Inc., Concord, CA, USA) using software version 3.0.1. The physical design, validation and measurement procedure have been described in detail elsewhere (15,16). The system measures body volume and body weight and calculates body density. Body composition is then calculated by means of a two-compartment model, assuming a fat mass density of 0.9007 g/mL and using fat-free mass density values based on data published by Fomon et al. (18). The validity of Fomon et al.0 s estimates of fat-free mass density in full-term newborns has recently been confirmed (19). Values for preterm infants are based on back-extrapolation using existing reference values for foetuses of different gestational ages (20,21). A recent study has
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 737–743
€rnqvist Olhager and To
reported good agreement between ADP and the isotope dilution technique in the when assessment of body composition in preterm infants (9). The method of measurement was as follows: first, a measuring board was used to assess the infant’s length. The infant0 s head was placed against the top of the measuring board and held in that position by one of the parents. The examiner (CT) straightened the infant’s legs and recorded the measurement. The infant’s body weight was then recorded using an electronic scale, which is part of the Pea Pod. Subsequently, the infant was placed without clothing in a chamber, which maintains a temperature of around 30°C, for about 2 min to measure body volume. While the body volume was measured a tight cap was used to keep the infant’s hair flat. All preterm infants except two were calm during the first measurement. Two infants cried and moved around at the start of the examination, but subsequently settled. One of these infants did not have a valid result and was excluded. During the second examination, nine infants initially cried but subsequently settled. Two infants did not settle and cried throughout the examination. Of the full-term infants, three cried and moved around during measurement. All infants were examined by the same person (CT). Ethical considerations The Regional Human Research Ethics Committee in € ping approved the study. Both parents of all infants Linko gave informed oral consent. Statistics Data were analysed using the statistical software SPSS for Windows, version 18.0 (Chicago, IL, USA). Values are expressed as means (SD). Repeated ANOVA, post hoc Tukey’s test and multiple regressions were used to identify significant differences between groups. Means were also compared using paired and unpaired t-tests. Significance was accepted when p < 0.05.
RESULTS Description of infants at birth The body weight, length and gestational age at birth of the late premature and full-term infants are presented in Table 1. The gestational age at birth of the preterm infants (n = 29) was 34.9 1.0 weeks and their birth weight 2443 395 grams. The weight-for-age z-score was 0.26 0.72 and the length-for-age z-score was 0.1 0.90 (22). The full-term infants (n = 29) were born in gestational week 38.7 1.2, and their birth weight was 3185 453 grams. Their weight-for-age and length-for-age z-scores were 0.83 0.34 and 0.69 0.58, respectively. Body composition of late premature infants during the first 10 days of life The body weights, fat mass and fat-free mass of the late preterm infants are shown in Table 2. The infants were examined, on average, at four-, six- and nine-day old. Four
Body composition in late preterm infants
Table 1 Gestational age, body length, head circumference and body weight at birth in late premature and full-term infants Premature infants* n = 29 (14 male) Gestational age (weeks) Range Length (cm) Range Head circumference (cm) Range Weight (g) Range Weight z-score‡ Length z-score§
Full-term infants† n = 29 (14 male)
35.0 (1.0)
38.7 (1.2)
(33.1–36.7) 46.0 (1.8) (43–49) 31.3 (0.5)
(37.0–40.7) 49.2 (2.1) (46–54) 36.2 (2.0)
(28–33) 2443 (395) (1685–3310) 0.26 0.72¶ 0.1 0.89¶
(35–39) 3185 (453) (2600–4310) 0.83 0.34¶ 0.69 0.58¶
Data are presented as mean (SD) and range. *Group One. † Group Two. ‡ Weight-for-age z-score. § Length-for-age z-score. ¶ (22).
infants were not examined on days six and nine. Between birth and the first examination, the infants lost 4.4 2.5% of their body weight. At the third examination, they had regained their birth weight. Between the first and third examinations, there was a significant increase (p < 0.05) in body weight, from 2323 363 to 2392 354 grams, and in fat-free mass, from 2176 297 to 2237 275 grams. The average increase in body weight was 69 57 grams, and the average increase in fat-free mass was 62 53 grams. During this period, the average change in body fat was 0.1 1.2% and the average increase in body fat 7.0 6.3 grams. This increase in fat mass was not significant. Body composition development of late premature infants until full-term PCA Table 3 shows the body weight, length, fat mass, fat-free mass, fat mass index and fat-free mass index of late preterm infants at the first measurement and at full-term PCA. The examinations were performed when the infants were on average four- and 25-day old. Between the two examinations, there were significant increases in body weight, length and head circumference. Fat mass increased from 153 113 to 348 181 grams, and fat mass as a percentage of body weight increased from 6.2 4.0 to 12.3 4.9. Fat-free mass increased from 2182 292 to 2631 309 grams. Fat mass accretion between the first and last examinations was 4.2 2.4 g/kg/day. The fat-free mass index was 10.3 1.1 kg/m2 at the first examination, increasing significantly to 11.4 1.0 kg/m2 at full-term PCA. The corresponding figures for fat mass index were 0.7 0.5–1.7 0.7 kg/m2, with this increase also significant (p < 0.05).
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 737–743
739
€rnqvist Olhager and To
Body composition in late preterm infants
Table 2 Body weight, fat mass and fat-free mass in 29 late preterm infants (four infants did not participate in examinations 2 and 3) assessed three times in the first 10 days of life Examination 1 2 3
Age (days)
Body weight (g)
4 (1) 6 (1) 9 (2)
Fat mass (%) †
2323 (363)* 2348 (356)* 2392 (354)*
4.9 (3.8) 4.4 (3.8)† 4.9 (3.3)†
Fat mass (g) †
150 (110) 135 (110)† 159 (111)†
Fat-free mass (g) 2176 (297)* 2216 (293)* 2237 (275)*
*Significant (p < 0.05) difference between measurements 1 and 2, 1 and 3, 2 and 3. † No significant difference between measurements 1 and 2, 1 and 3, 2 and 3. Data are presented as means (SD).
Table 3 Body weight, length, fat mass, fat-free mass, fat mass index and fat-free mass index in 29 late preterm infants (Group One) at first measurement and at full-term PCA
PCA (weeks) Age (days) Weight (g) Length (cm) Fat mass (%) Fat mass (g) Fat-free mass (g) Fat mass index kg/m2 Fat-free mass index kg/m2
First measurement
Full-term PCA
p-Value*
95% CI
35.0 4 2333 46 6.2 153 2182 0.7 10.3
38.7 25 3012 47 12.3 384 2631 1.7 11.4
REGULAR ARTICLE
Body composition in late preterm infants in the first 10 days of life and at full term Elisabeth Olhager ([email protected]), Caroline T€ornqvist €ping, Sweden Division of Paediatrics, Department of Clinical and Experimental Medicine, Faculty of Health Science, Linkoping University, Linko
Keywords Air displacement plethysmography, Body composition, Fat mass, Fat-free mass, Preterm infants Correspondence E Olhager, Department of Neonatology, Skane University Hospital, SE-221 85 Lund, Sweden. Tel: +46 46 178286 | Email: [email protected] Received 29 September 2013; revised 1 February 2014; accepted 10 March 2014. DOI:10.1111/apa.12632
ABSTRACT Aim: To investigate changes in body weight, fat-free mass, fat mass and percentage of body fat during early life and at full-term postconceptional age (PCA) in preterm infants born after 32 gestational weeks and before 37. Methods: Twenty-nine late preterm infants underwent growth and body composition assessment by air displacement plethysmography (ADP) at the age of 4 days and at fullterm PCA. In 25 of these infants, body composition was assessed three times between days four and nine of life. The preterm infants were compared with 29 full-term infants, matched for gestational age, sex and body weight. Results: There was a significant increase in birth weight and fat-free mass between days four and nine of life. Preterm infants had significantly more body fat 382 180 g vs 287 160 g than full-term infants at full-term PCA. Preterm infants showed poor linear growth between birth and full-term PCA. Conclusion: Weight gain after the initial postnatal weight loss consists of gain in fat-free mass. At full-term PCA, preterm infants were stunted. When compared with full-term new born infants matched for body weight and gestational age, preterm infants had more body fat and a higher percentage of body fat.
INTRODUCTION Preterm infants often experience early postnatal growth failure, which is already evident at full-term postconceptional age (PCA) and may be associated with a negative long-term neurological outcome (1). Aggressive nutritional management has been proposed to minimize later developmental delays, the goal being to achieve a postnatal weight gain approximately equal to foetal growth rates (2). However, rapid weight gain in early infancy has been associated with increased risks of obesity and metabolic syndrome later in life (3). Furthermore, it has been shown that children who are born prematurely have an isolated reduction in insulin sensitivity, which may be a risk factor for type 2 diabetes mellitus (4). In recent years, there has been increasing focus on the quality of growth in preterm infants (5,6). Studies comparing the body composition of preterm infants at full-term PCA with that of full-term newborns show preterm infants are not only shorter and lighter, but they also have more body fat and less fat-free mass (7). This is alarming, because this pattern of growth may correlate with impaired cognitive outcome (1,5). Most studies of the body composition of preterm infants have been carried out in infants born before 32 gestational weeks (1,6,7). A study of late preterm Italian infants born after gestational week 32, but before 37 completed gestational weeks, found rapid catch-up growth in fat mass between birth and one-month old (8,9). In Sweden, this group of infants represents 3–4% of all newborns and, in
fact, almost 25% of infants admitted to neonatal units, making them by far the largest patient group (10). Although these late preterm infants are relatively healthy compared with infants born before 32 completed gestational weeks, they have higher mortality and morbidity than full-term newborn infants (10). The period around birth is very important, as the first days of postnatal life are a time of enormous change (11). Several studies have highlighted the high-fat content in preterm infants at full-term PCA, but little attention has been paid to their body composition development during the first postnatal days (12). One study reported data on the body composition of preterm and full-term infants within 48 h of birth, stating that the proportion of body fat in late
Key notes
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 737–743
Conflicting data exist regarding early and late changes in body composition in late preterm infants. We found that weight gain after the initial postnatal weight loss consisted of gain in fat-free mass and preterm infants (n = 29) had a higher percentage of body fat than full-term infants (n = 29). This pattern of growth and body composition development may be associated with increased risks of obesity and the metabolic syndrome in later life.
737
€rnqvist Olhager and To
Body composition in late preterm infants
preterm infants, assessed by dual-energy X-ray absorptiometry (DEXA), was as high as 13–14% (13). In 2004, equipment based on the air displacement plethysmography (ADP) technique became available, enabling accurate, quick and noninvasive assessment of body composition in infants weighing between one and eight kilograms (9,14,15). This technique has subsequently been used to measure the body composition of full-term and preterm infants. It is well accepted by parents, healthcare staff and infants and is therefore well suited for clinical studies. We used the ADP technique in a group of late preterm infants to study changes in body composition during the early postnatal period. Our first aim was to describe changes in body weight, fat mass and fat-free mass in such infants during the first 10 days of life. Our second aim was to compare their body composition at full-term PCA with corresponding values for full-term new born infants matched for PCA, sex and weight.
MATERIALS AND METHODS Study design Body weight, fat-free mass and fat mass were assessed in 29 preterm infants (Group One). The infants were examined on day four one of life, on two additional occasions during the first 10 days of life and at full-term PCA. Four infants were not assessed on the following two occasions. Values obtained at full-term PCA were compared with those for 29 full-term newborn infants (Group Two). For this comparison, infants were matched for sex, body weight (100 g) and PCA (3 days). Infants in Group Two were examined on day six two of life. Figure 1 shows the infants who participated in the study. Preterm infants Between February 2008 and June 2009, 166 preterm infants, born after at least 32 gestational weeks, were € ping admitted to the neonatal intensive care unit at Linko
Group 1 n = 29 preterm infants, investigated on day four of life
Four preterm infants were not eligable for investigations on day 6 and 9 of life.
Group 1 n = 29 preterm infants investigated att full-term post conceptional age
Group 2 n = 29 full-term infants
Figure 1 Flow diagram of the infants who participated in the study.
738
University Hospital. Gestational age was based on the date of the last menstrual period and ultrasound in gestational week 11–12. Postconceptional age was calculated using chronological age plus gestational age. Forty-one of these infants met the following criteria: birth weight over 1500 grams, singletons, weight and length appropriate for gestational age according to Swedish growth reference values (16), no need for respiratory support (ventilator, continued airway pressure or extra oxygen), no need for parenteral nutrition and no sepsis or malformation. Parents were asked for permission for their child to participate in the study, and permission was granted for 30 infants (29 infants had valid results). These infants were all fed according to current practice at the neonatal unit, which includes special efforts to initiate and maintain maternal lactation. As most preterm infants are unable to suck effectively, breast milk was initially fed through a nasogastric tube. If the mother was unable to provide breast milk, the infants were fed formula (Pepti Junior, Mead Johnsson). On day four of life, nine infants received formula, 13 received formula plus their mother’s breast milk, and seven only received their mother’s breast milk. At full-term PCA, two infants were fed formula, four were fed formula plus breast milk, and 23 only received breast milk. Feeding regimes were not recorded between discharge from the unit and the day of assessment. Full-term infants Twenty-nine healthy full-term newborn infants were € ping University recruited from the maternity ward at Linko Hospital. Fourteen had participated in a previous study (17). The infants were fed according to the guidelines of the maternity unit, where all mothers are encouraged to breastfeed. At the time of investigation, two infants were formula fed, two received formula plus breast milk and 25 were completely breastfed. Anthropometry at birth In the delivery room, all infants were weighed without clothing on an electronic baby scale (Tanita Corporation, Tokyo, Japan) and their length measured by means of a measuring board. Head circumference was measured with a plastic measuring band. Body composition Body composition was assessed using an ADP system (Pea Pod, Cosmed USA Inc., Concord, CA, USA) using software version 3.0.1. The physical design, validation and measurement procedure have been described in detail elsewhere (15,16). The system measures body volume and body weight and calculates body density. Body composition is then calculated by means of a two-compartment model, assuming a fat mass density of 0.9007 g/mL and using fat-free mass density values based on data published by Fomon et al. (18). The validity of Fomon et al.0 s estimates of fat-free mass density in full-term newborns has recently been confirmed (19). Values for preterm infants are based on back-extrapolation using existing reference values for foetuses of different gestational ages (20,21). A recent study has
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 737–743
€rnqvist Olhager and To
reported good agreement between ADP and the isotope dilution technique in the when assessment of body composition in preterm infants (9). The method of measurement was as follows: first, a measuring board was used to assess the infant’s length. The infant0 s head was placed against the top of the measuring board and held in that position by one of the parents. The examiner (CT) straightened the infant’s legs and recorded the measurement. The infant’s body weight was then recorded using an electronic scale, which is part of the Pea Pod. Subsequently, the infant was placed without clothing in a chamber, which maintains a temperature of around 30°C, for about 2 min to measure body volume. While the body volume was measured a tight cap was used to keep the infant’s hair flat. All preterm infants except two were calm during the first measurement. Two infants cried and moved around at the start of the examination, but subsequently settled. One of these infants did not have a valid result and was excluded. During the second examination, nine infants initially cried but subsequently settled. Two infants did not settle and cried throughout the examination. Of the full-term infants, three cried and moved around during measurement. All infants were examined by the same person (CT). Ethical considerations The Regional Human Research Ethics Committee in € ping approved the study. Both parents of all infants Linko gave informed oral consent. Statistics Data were analysed using the statistical software SPSS for Windows, version 18.0 (Chicago, IL, USA). Values are expressed as means (SD). Repeated ANOVA, post hoc Tukey’s test and multiple regressions were used to identify significant differences between groups. Means were also compared using paired and unpaired t-tests. Significance was accepted when p < 0.05.
RESULTS Description of infants at birth The body weight, length and gestational age at birth of the late premature and full-term infants are presented in Table 1. The gestational age at birth of the preterm infants (n = 29) was 34.9 1.0 weeks and their birth weight 2443 395 grams. The weight-for-age z-score was 0.26 0.72 and the length-for-age z-score was 0.1 0.90 (22). The full-term infants (n = 29) were born in gestational week 38.7 1.2, and their birth weight was 3185 453 grams. Their weight-for-age and length-for-age z-scores were 0.83 0.34 and 0.69 0.58, respectively. Body composition of late premature infants during the first 10 days of life The body weights, fat mass and fat-free mass of the late preterm infants are shown in Table 2. The infants were examined, on average, at four-, six- and nine-day old. Four
Body composition in late preterm infants
Table 1 Gestational age, body length, head circumference and body weight at birth in late premature and full-term infants Premature infants* n = 29 (14 male) Gestational age (weeks) Range Length (cm) Range Head circumference (cm) Range Weight (g) Range Weight z-score‡ Length z-score§
Full-term infants† n = 29 (14 male)
35.0 (1.0)
38.7 (1.2)
(33.1–36.7) 46.0 (1.8) (43–49) 31.3 (0.5)
(37.0–40.7) 49.2 (2.1) (46–54) 36.2 (2.0)
(28–33) 2443 (395) (1685–3310) 0.26 0.72¶ 0.1 0.89¶
(35–39) 3185 (453) (2600–4310) 0.83 0.34¶ 0.69 0.58¶
Data are presented as mean (SD) and range. *Group One. † Group Two. ‡ Weight-for-age z-score. § Length-for-age z-score. ¶ (22).
infants were not examined on days six and nine. Between birth and the first examination, the infants lost 4.4 2.5% of their body weight. At the third examination, they had regained their birth weight. Between the first and third examinations, there was a significant increase (p < 0.05) in body weight, from 2323 363 to 2392 354 grams, and in fat-free mass, from 2176 297 to 2237 275 grams. The average increase in body weight was 69 57 grams, and the average increase in fat-free mass was 62 53 grams. During this period, the average change in body fat was 0.1 1.2% and the average increase in body fat 7.0 6.3 grams. This increase in fat mass was not significant. Body composition development of late premature infants until full-term PCA Table 3 shows the body weight, length, fat mass, fat-free mass, fat mass index and fat-free mass index of late preterm infants at the first measurement and at full-term PCA. The examinations were performed when the infants were on average four- and 25-day old. Between the two examinations, there were significant increases in body weight, length and head circumference. Fat mass increased from 153 113 to 348 181 grams, and fat mass as a percentage of body weight increased from 6.2 4.0 to 12.3 4.9. Fat-free mass increased from 2182 292 to 2631 309 grams. Fat mass accretion between the first and last examinations was 4.2 2.4 g/kg/day. The fat-free mass index was 10.3 1.1 kg/m2 at the first examination, increasing significantly to 11.4 1.0 kg/m2 at full-term PCA. The corresponding figures for fat mass index were 0.7 0.5–1.7 0.7 kg/m2, with this increase also significant (p < 0.05).
©2014 Foundation Acta Pædiatrica. Published by John Wiley & Sons Ltd 2014 103, pp. 737–743
739
€rnqvist Olhager and To
Body composition in late preterm infants
Table 2 Body weight, fat mass and fat-free mass in 29 late preterm infants (four infants did not participate in examinations 2 and 3) assessed three times in the first 10 days of life Examination 1 2 3
Age (days)
Body weight (g)
4 (1) 6 (1) 9 (2)
Fat mass (%) †
2323 (363)* 2348 (356)* 2392 (354)*
4.9 (3.8) 4.4 (3.8)† 4.9 (3.3)†
Fat mass (g) †
150 (110) 135 (110)† 159 (111)†
Fat-free mass (g) 2176 (297)* 2216 (293)* 2237 (275)*
*Significant (p < 0.05) difference between measurements 1 and 2, 1 and 3, 2 and 3. † No significant difference between measurements 1 and 2, 1 and 3, 2 and 3. Data are presented as means (SD).
Table 3 Body weight, length, fat mass, fat-free mass, fat mass index and fat-free mass index in 29 late preterm infants (Group One) at first measurement and at full-term PCA
PCA (weeks) Age (days) Weight (g) Length (cm) Fat mass (%) Fat mass (g) Fat-free mass (g) Fat mass index kg/m2 Fat-free mass index kg/m2
First measurement
Full-term PCA
p-Value*
95% CI
35.0 4 2333 46 6.2 153 2182 0.7 10.3
38.7 25 3012 47 12.3 384 2631 1.7 11.4
![[Growth and body composition changes in late preterm infants in the first months of life].](/assets/img/hold.png)
