| Objective:To explore the associations between early-term birth and infant physical growth and its trajectory patterns,so as to provide scientific evidence for prevention and control.Methods:A total of 3421 term infants born at Wuhan were included in this longitudinal study.Medical records at birth of these infants and general information of their parents were collected,and physical growth indicators were measured at 1,3,6,8 and 12 months of age.Standardized Z-scores conversion was performed for physical growth indicators at each time point and length-for-age Z-Score(LAZ),weight-for-age Z-Score(WAZ),body mass index-for-age Z-Score(BMIZ),weight-for-length Z-Score(WLZ)and head circumference-for-age Z-Score(HCAZ)were obtained.Single sample t-test was used to compare the differences of measured values of physical indicators between the subjects and the physical growth standards of China and WHO.Analysis of covariance(ANCOVA)and t-test were used to compare the differences of measured values and Z-scores of physical growth indicators between early-term infants and full-term infants.Theχ~2test was used to compare the distribution of growth trajectory patterns between early-term and full-term infants.Group based trajectory modeling(GBTM)was used to identify the growth trajectory patterns in length,weight,BMI and HC among term infants.The multinomial logistic regression analysis was used to explore the association between early-term birth and growth trajectory patterns.Results:1 There were 1028(30.05%)early-term infants and 2393(69.95%)full-term infants included in our study,which maintained a high follow-up rate in all six follow-up time points.There was no significant difference in chronological age between early-term infants and full-term infants at every follow-up.2 The physical growth of the subjects was on well.It was better than WHO standards at each follow-up.It was also better than Chinese standards at each follow-up except for length at 12 months of age for girls and head circumference at 6months of age for boys.3 Compared with full-term infants,the physical growth of early-term infants was lower than that of full-term infants at the earlier follow-up points in infancy.According to the analysis of covariance(ANCOVA),early-term infants were 0.45cm,0.54cm and 0.33cm lower than full-term infants in length at birth,1 month and 3months,were 0.18kg and 0.11kg lower in weight at birth and 1 month,and were0.17cm and 0.12cm lower in head circumference at 1 month and 3 months,respectively.In the comparison of the Z values,the results were similar.4 By using GBTM,we identified three growth patterns,namely“low growth”,“moderate growth”and“high growth”.The proportion of“low growth”trajectory in length,weight and head circumference decreased with the increase of gestational age.After adjusting for confounding factors,the results of the multinomial logistic regression model showed that early-term infants were more likely to experience“low growth”trajectory in length(OR:1.40,95%CI:1.19-1.66)and“low growth”trajectory in weight(OR:1.29,95%CI:1.09-1.53),but less likely to experience“high growth”trajectory in length(OR:0.72,95%CI:0.56-0.92).5 In the results of gender stratification analysis,the association between early-term infant and the“low growth”trajectory in length and weight was found in both boys and girls.But the association between early-term infant and the“high growth”trajectory in length was only found in girls(OR:0.62,95%CI:0.43-0.90).Besides,the association between early-term infant and the“high growth”trajectory in weight-for-length was also found only in girls(OR:1.46,95%CI:1.05-2.02).Conclusions:The physical growth of early-term infants were lower than that of full-term infants at the earlier follow-up points of infancy.Even if there was no difference between early-term and full-term infants at the later follow-up points of infancy,early term infants were at an increased risk of experiencing"low growth"trajectory in length and weight.Our results suggest that it is necessary to strengthen the monitoring and management of the physical growth of early-term infants in order to promote their healthy growth. |
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