Parental axial lengths and prenatal conditions related to child axial length: The TMM BirThree Cohort Study

Purpose: We investigated the association between actual parental axial length, prenatal conditions, and the axial length in preschool children. Design: Cohort study Methods: This study included 1,819 children (mean age: 4.2 ± 0.4 years, 50.1% girls) and their parents enrolled in the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study in Japan. Axial length was measured using OA-1000 Optical Biometer. A marginal model with generalized estimating equations was used for association analysis. Variables included the child's age, sex, height at the second wave, prenatal conditions (large for gestational age [LGA], resuscitation, acidosis, small placenta at birth, multiple pregnancies, maternal hypertensive disorders of pregnancy), parental age, and the mean axial length of both parents’ eyes at the second wave. Path analysis was performed to investigate the relationships among the variables. Results: Axial length was shorter in girls than in boys (regression coefficient (β) [95% confidence interval] -0.52 [-0.57, -0.47]). Age and height were associated with longer axial lengths (0.10 [0.022, 0.18] and 0.025 [0.019, 0.031], respectively). Parental axial lengths were positively associated with children's axial lengths (0.12 [0.10, 0.14] for fathers and 0.12 [0.094, 0.14] for mothers). LGA was associated with longer axial lengths (0.12 [0.033, 0.20]), whereas small placenta and multiple pregnancies were associated with shorter axial lengths (-0.11 [-0.17, -0.045] and -0.21 [-0.33, -0.091], respectively). The path coefficient for both parents’ axial lengths in relation to their children's axial lengths was 0.23. Conclusion: Parental axial lengths and prenatal conditions may determine axial length during early life.