Original article
Incidence of short stature at 3 years of age in late preterm infants: a population-based study Miwako Nagasaka,1 Ichiro Morioka,1 Tomoyuki Yokota,1 Kaori Fujita,1 Daisuke Kurokawa,1 Tsubasa Koda,1 Akio Shibata,1 Hideto Yamada,2 Yoshiya Ito,3 Eiko Uchino,4 Chika Shirai,4 Kazumoto Iijima1 ▸ Additional material is published online only. To view please visit the journal online (http://dx.doi.org/10.1136/ archdischild-2014-307045). 1
Departments of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan 2 Obstetrics and Gynecology, Kobe University Graduate School of Medicine, Kobe, Japan 3 The Japanese Red Cross Hokkaido College of Nursing, Kitami, Japan 4 Kobe City Public Health Center, Kobe, Japan Correspondence to Dr Ichiro Morioka, Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe 6500017, Japan; [email protected] MN and IM contributed equally. Received 26 June 2014 Accepted 11 September 2014 Published Online First 26 September 2014
ABSTRACT Objectives This study aimed to investigate the incidence of short stature at 3 years of age in a Japanese cohort of late preterm infants who were born at 34–36 weeks’ gestational age (GA). We compared these late preterm infants with term infants (37– 41 weeks’ GA), and evaluated the effect of birth weight on the incidence of short stature. Methods A longitudinal population-based study of 26 970 neonates who were born between 34 weeks’ and 41 weeks’ GA in 2006–2008 was conducted in Kobe, Japan. Of these neonates, 1414 were late preterm and 25 556 were term infants. The late preterm infants were then divided into three subgroups based on birth weight as determined by Japanese neonatal anthropometric charts for GA at birth: large-for-GA (n=140), appropriate-for-GA (AGA, n=1083), and smallfor-GA (SGA, n=191). The incidence of short stature at 3 years of age was calculated in the late preterm group and compared with that in the term group, and between the AGA and SGA groups with late preterm birth. Results The incidence of short stature in the late preterm group was 2.9%, which was significantly higher than that in the term group (1.4%). Late preterm SGA infants developed short stature with a significantly higher (9.4%) incidence than that of late preterm AGA infants (2.1%). Conclusions The incidence of short stature in 3-yearold children who were late preterm infants has a 2-fold higher risk than that in term infants. The risk of developing short stature is increased 4.5-fold if they are SGA.
INTRODUCTION
To cite: Nagasaka M, Morioka I, Yokota T, et al. Arch Dis Child 2015;100:250–254. 250
Late preterm infants are defined as those who are born at 34–36 weeks’ gestational age (GA).1 During the last 30 years, births have decreased from 1.58 million in 1980 to 1.03 million in 2012 in Japan. However, the proportion of preterm births between 32 weeks’ and 36 weeks’ GA, including late preterm birth, increased by 3.6% in 1980 to 5.0% in 2012.2 Therefore, health outcomes in late preterm infants have attracted attention in Japan. Late preterm infants are at higher risk of neonatal morbidity than term infants who are born at 37–41 weeks’ GA, with feeding difficulties, hypoglycaemia, jaundice, respiratory distress and sepsis.1 3 Neurodevelopmental and educational outcomes are also worse in late preterm infants compared with those in term infants.4–6 Growth impairment, such as short stature, is an important
What is already known on this topic? ▸ Late preterm infants have an increased risk of neonatal mortality and morbidity including neurodevelopmental disorders in infancy when compared with term infants.
What this study adds? ▸ Late preterm infants have a twofold higher risk of short stature at 3 years of age than term infants. ▸ The risk of short stature is increased by 4.5-fold if they are born small-for-gestational age, regardless of birth length and ponderal index values.
factor to examine in the follow-up of late preterm infants. However, no population-based studies have focused on the incidence of short stature in late preterm infants. One hypothesis is that late preterm birth is a risk factor for short stature. Additionally, because it is not clear if late preterm birth and some physical factors at birth are risk factors for short stature, another hypothesis is that the ponderal index (PI), which indicates the intrauterine nutritional state (possibly, fetal programming), is used as a predictive index for short stature in infancy. The objectives of this population-based study were (1) to longitudinally investigate the incidence of short stature at 3 years of age in children who were late preterm infants using a cohort of neonates who were born and followed up in Kobe, Japan, and to compare it between children who were late preterm and term infants, and (2) to investigate the effects of GA and physical factors at birth (birth weight (BW), birth length (BL), and PI) on the incidence of short stature at 3 years of age.
PATIENTS AND METHODS Study design A population-based study of 32 154 children who were born between 2006 and 2008 and followed up with height and weight measurements until 3 years (36–47 months) of age was conducted in Kobe City, Japan (figure 1). Written informed
Nagasaka M, et al. Arch Dis Child 2015;100:250–254. doi:10.1136/archdischild-2014-307045
Original article
Figure 1 Flow chart of the subjects. consent from the parents of the children was obtained. Information regarding data at birth, such as GA, BW, BL, the mother’s history of childbirth, pregnancy-induced hypertension and smoking during pregnancy were collected on the basis of the maternity health records, which were managed in Kobe City Public Health Centers. The children’s height and weight were measured at 3 years of age and collected at different Kobe City Public Health Centers, which are located at 11 places in Kobe. Data were managed based on the act of personal information protection in Kobe City. The analysis using anonymous data was approved by the Planning and Coordination Bureau of Kobe, and was then carried out at Kobe University Graduate School of Medicine.
Subjects The height and weight data at 3 years of age were recorded in 32 154 children. Of these children, 5184 were excluded because of insufficient data for analysis of this study (n=4798) or gestation at birth was ≥42 weeks (n=128) or ≤33 weeks (n=258). Of the remaining 26 970 children, 1414 (5.2%) were late preterm births and 25 556 (94.8%) were term births. The 25 556 term infants were divided into full term (39–41 weeks’ GA, n=17 832) and early term infants (37–38 weeks’ GA, n=7724).
Each group was then divided into three subgroups based on Japanese neonatal anthropometric charts for GA at birth:7 BW ≥ the 90th centile (large-for-gestational age (LGA)), BW between the 10th to 90th centiles (appropriate-for-gestational age (AGA)), and BW < the 10th centile (small-for-gestational age, (SGA), figure 1). Among the 4798 children with insufficient data, 85 were born at ≤33 weeks’ GA, 207 were born at 34–36 weeks’ GA, 3201 were born at 37–41 weeks’ GA, 11 were born at ≥42 weeks GA, and 1294 had an unknown GA. The proportion of effective and insufficient data was similar in those born at 34–36 weeks’ GA and those born at 37–41 weeks’ GA (34– 36 weeks’ GA: effective data, n=1414 (87.2%) and insufficient data, n=207 (12.8%); 37–41 weeks GA: effective data, n=25 556 (88.9%) and insufficient data, n=3201 (11.1%)).
METHODS We analysed (1) the background characteristics at birth, (2) the proportion of SGA infants, (3) the incidence of short stature, (4) the severity in short stature, (5) the effects of GA and BW on the incidence of short stature and (6) the effects of BL and PI on the incidence of short stature, and compared them among the groups.
Nagasaka M, et al. Arch Dis Child 2015;100:250–254. doi:10.1136/archdischild-2014-307045
251
Original article Definitions and calculations BL was the length from the crown to heel at birth. All neonates, regardless of GA, underwent measurement of the BL with a measuring tape or ruler by trained midwives or nurses. The newborns were classified as BL ≥ 10th centile and BL
Incidence of short stature at 3 years of age in late preterm infants: a population-based study Miwako Nagasaka,1 Ichiro Morioka,1 Tomoyuki Yokota,1 Kaori Fujita,1 Daisuke Kurokawa,1 Tsubasa Koda,1 Akio Shibata,1 Hideto Yamada,2 Yoshiya Ito,3 Eiko Uchino,4 Chika Shirai,4 Kazumoto Iijima1 ▸ Additional material is published online only. To view please visit the journal online (http://dx.doi.org/10.1136/ archdischild-2014-307045). 1
Departments of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan 2 Obstetrics and Gynecology, Kobe University Graduate School of Medicine, Kobe, Japan 3 The Japanese Red Cross Hokkaido College of Nursing, Kitami, Japan 4 Kobe City Public Health Center, Kobe, Japan Correspondence to Dr Ichiro Morioka, Department of Pediatrics, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe 6500017, Japan; [email protected] MN and IM contributed equally. Received 26 June 2014 Accepted 11 September 2014 Published Online First 26 September 2014
ABSTRACT Objectives This study aimed to investigate the incidence of short stature at 3 years of age in a Japanese cohort of late preterm infants who were born at 34–36 weeks’ gestational age (GA). We compared these late preterm infants with term infants (37– 41 weeks’ GA), and evaluated the effect of birth weight on the incidence of short stature. Methods A longitudinal population-based study of 26 970 neonates who were born between 34 weeks’ and 41 weeks’ GA in 2006–2008 was conducted in Kobe, Japan. Of these neonates, 1414 were late preterm and 25 556 were term infants. The late preterm infants were then divided into three subgroups based on birth weight as determined by Japanese neonatal anthropometric charts for GA at birth: large-for-GA (n=140), appropriate-for-GA (AGA, n=1083), and smallfor-GA (SGA, n=191). The incidence of short stature at 3 years of age was calculated in the late preterm group and compared with that in the term group, and between the AGA and SGA groups with late preterm birth. Results The incidence of short stature in the late preterm group was 2.9%, which was significantly higher than that in the term group (1.4%). Late preterm SGA infants developed short stature with a significantly higher (9.4%) incidence than that of late preterm AGA infants (2.1%). Conclusions The incidence of short stature in 3-yearold children who were late preterm infants has a 2-fold higher risk than that in term infants. The risk of developing short stature is increased 4.5-fold if they are SGA.
INTRODUCTION
To cite: Nagasaka M, Morioka I, Yokota T, et al. Arch Dis Child 2015;100:250–254. 250
Late preterm infants are defined as those who are born at 34–36 weeks’ gestational age (GA).1 During the last 30 years, births have decreased from 1.58 million in 1980 to 1.03 million in 2012 in Japan. However, the proportion of preterm births between 32 weeks’ and 36 weeks’ GA, including late preterm birth, increased by 3.6% in 1980 to 5.0% in 2012.2 Therefore, health outcomes in late preterm infants have attracted attention in Japan. Late preterm infants are at higher risk of neonatal morbidity than term infants who are born at 37–41 weeks’ GA, with feeding difficulties, hypoglycaemia, jaundice, respiratory distress and sepsis.1 3 Neurodevelopmental and educational outcomes are also worse in late preterm infants compared with those in term infants.4–6 Growth impairment, such as short stature, is an important
What is already known on this topic? ▸ Late preterm infants have an increased risk of neonatal mortality and morbidity including neurodevelopmental disorders in infancy when compared with term infants.
What this study adds? ▸ Late preterm infants have a twofold higher risk of short stature at 3 years of age than term infants. ▸ The risk of short stature is increased by 4.5-fold if they are born small-for-gestational age, regardless of birth length and ponderal index values.
factor to examine in the follow-up of late preterm infants. However, no population-based studies have focused on the incidence of short stature in late preterm infants. One hypothesis is that late preterm birth is a risk factor for short stature. Additionally, because it is not clear if late preterm birth and some physical factors at birth are risk factors for short stature, another hypothesis is that the ponderal index (PI), which indicates the intrauterine nutritional state (possibly, fetal programming), is used as a predictive index for short stature in infancy. The objectives of this population-based study were (1) to longitudinally investigate the incidence of short stature at 3 years of age in children who were late preterm infants using a cohort of neonates who were born and followed up in Kobe, Japan, and to compare it between children who were late preterm and term infants, and (2) to investigate the effects of GA and physical factors at birth (birth weight (BW), birth length (BL), and PI) on the incidence of short stature at 3 years of age.
PATIENTS AND METHODS Study design A population-based study of 32 154 children who were born between 2006 and 2008 and followed up with height and weight measurements until 3 years (36–47 months) of age was conducted in Kobe City, Japan (figure 1). Written informed
Nagasaka M, et al. Arch Dis Child 2015;100:250–254. doi:10.1136/archdischild-2014-307045
Original article
Figure 1 Flow chart of the subjects. consent from the parents of the children was obtained. Information regarding data at birth, such as GA, BW, BL, the mother’s history of childbirth, pregnancy-induced hypertension and smoking during pregnancy were collected on the basis of the maternity health records, which were managed in Kobe City Public Health Centers. The children’s height and weight were measured at 3 years of age and collected at different Kobe City Public Health Centers, which are located at 11 places in Kobe. Data were managed based on the act of personal information protection in Kobe City. The analysis using anonymous data was approved by the Planning and Coordination Bureau of Kobe, and was then carried out at Kobe University Graduate School of Medicine.
Subjects The height and weight data at 3 years of age were recorded in 32 154 children. Of these children, 5184 were excluded because of insufficient data for analysis of this study (n=4798) or gestation at birth was ≥42 weeks (n=128) or ≤33 weeks (n=258). Of the remaining 26 970 children, 1414 (5.2%) were late preterm births and 25 556 (94.8%) were term births. The 25 556 term infants were divided into full term (39–41 weeks’ GA, n=17 832) and early term infants (37–38 weeks’ GA, n=7724).
Each group was then divided into three subgroups based on Japanese neonatal anthropometric charts for GA at birth:7 BW ≥ the 90th centile (large-for-gestational age (LGA)), BW between the 10th to 90th centiles (appropriate-for-gestational age (AGA)), and BW < the 10th centile (small-for-gestational age, (SGA), figure 1). Among the 4798 children with insufficient data, 85 were born at ≤33 weeks’ GA, 207 were born at 34–36 weeks’ GA, 3201 were born at 37–41 weeks’ GA, 11 were born at ≥42 weeks GA, and 1294 had an unknown GA. The proportion of effective and insufficient data was similar in those born at 34–36 weeks’ GA and those born at 37–41 weeks’ GA (34– 36 weeks’ GA: effective data, n=1414 (87.2%) and insufficient data, n=207 (12.8%); 37–41 weeks GA: effective data, n=25 556 (88.9%) and insufficient data, n=3201 (11.1%)).
METHODS We analysed (1) the background characteristics at birth, (2) the proportion of SGA infants, (3) the incidence of short stature, (4) the severity in short stature, (5) the effects of GA and BW on the incidence of short stature and (6) the effects of BL and PI on the incidence of short stature, and compared them among the groups.
Nagasaka M, et al. Arch Dis Child 2015;100:250–254. doi:10.1136/archdischild-2014-307045
251
Original article Definitions and calculations BL was the length from the crown to heel at birth. All neonates, regardless of GA, underwent measurement of the BL with a measuring tape or ruler by trained midwives or nurses. The newborns were classified as BL ≥ 10th centile and BL
