The trajectories of physical growth in 4 months postnatal corrected age among preterm infants discharged from neonatal intensive care units and associated factors: A prospective study

Abstract

Objectives: Growth retardation is a risk for premature infants. In addition to demographic and perinatal factors, preterm infants' physical growth may be affected by neonatal intensive care unit (NICU) stress, maternal postpartum depression, and mother-infant interaction. This study aimed to investigate the trajectories of physical growth in 4 months corrected age among preterm infants discharged from the NICU and the impactors on these trajectories.

Methods: A prospective study was conducted among 318 preterm infants from September 2019 to April 2021 in Shanghai, China. Latent growth modeling was applied to identify the weight, length, and head circumference growth trajectories in 4 months corrected age and explore the effects of demographic and medical characteristics, infant stress during NICU stay, maternal postpartum depression, and mother-infant interaction on each trajectory.

Results: Unconditional latent growth models showed curve trajectories with increasingly slower growth in weight, length, and head circumference until 4 months of corrected age. Conditional latent growth models showed that a longer length of stay in the NICU and more skin punctures were negatively associated with weight at 40 weeks corrected gestational age (β = -0.43 and -0.19, respectively, P < 0.05). The maternal postpartum depression between 40 weeks corrected gestational age and 1 month corrected postnatal age was associated with a lower growth rate of length (β = -0.17, P = 0.040), while between 2 and 3 months corrected postnatal age, there were lower growth rates of weight and head circumference (β = -0.15 and -0.19, respectively, P < 0.05). The mother-infant interaction scores between 40 weeks corrected gestational age and 1 month corrected postnatal age negatively predicted the growth rate of weight (β = -0.19, P = 0.020).

Conclusion: The physical growth trajectories of preterm infants discharged from the NICU were influenced by infant stress during the NICU stay, maternal postpartum depression and mother-infant interaction.

Keywords: Growth; Latent growth model; Mother-infant interaction; Neonatal intensive care unit; Postpartum depression; Premature infant.

Fig. 1

Growth curve of preterm infants in this study and the WHO standards.

Fig. 2

The measurement of conditional Latent Growth Models with covariates for the trajectories of weight, length, and head circumference of preterm infants. The covariates were maternal age, twin pregnancy, sex, gestational age at birth, birth weight, SGA, breastfeeding during the NICU stay, LOS, skin punctures, MV, maternal depression during T1–T2 and T3–T4, and mother-infant interaction during T1–T2 and T3–T4. For the conditional LGM of weight, the slope factor loadings were set as 0, 1.0, 1.8, 2.4, and 2.9 at T1–T5, respectively; for the length model, the slope factor loadings were set as 0, 1.0, 2.0, 2.7, and 3.3 at T1–T5, respectively; for the HC model, the slope factor loadings were set as 0, 1.0, 2.0, 2.7, and 3.2 at T1–T5, respectively. Abbreviation： HC = head circumference. LGM = Latent Growth Model. LOS = length of stay in the NICU. MV = mechanical ventilation. SGA = small for gestational age infant. T1 = 40 weeks of corrected gestational age. T2 = 1 month of corrected postnatal age. T3 = 2 months of corrected postnatal age. T4 = 3 months of corrected postnatal age. T5 = 4 months of corrected postnatal age.