Dr. Mary Schooling, professor at the CUNY Graduate School of Public Health and Health Policy and an international team of investigators examined the association of birth order with early adolescent growth, pubertal onset, blood pressure and size. The findings were published in PLoS One.
[Photo: Dr. Mary Schooling]
The research team examined the associations of birth order (firstborn or later born) with birth weight-for-gestational age, length/height and body mass index z-scores during infancy, childhood, and puberty. Data were from a population-representative Chinese birth cohort, the “Children of 1997” (n = 8,327).
Compared with children born later, firstborns had lower birth weight-for-gestational age, lower infant BMI, greater childhood height, and BMI, but not greater pubertal BMI. Data were adjusted for sex, parental age, birthplace, education, and income. Firstborns had earlier onset of pubic hair, but not breast or genitalia, development. At age 13 years, firstborns had greater BMI, but not height and similar blood pressure.
The research team concluded that differences by birth order continue into early adolescence which could indicate long-term cardiovascular risk.