Size at birth, infant growth, and age at pubertal development in boys and girls

Abstract

Purpose

This study investigated whether size at birth and infant growth were associated with age of indicators of pubertal development in boys and girls. We hypothesized that restricted fetal growth and accelerated infant growth lead to earlier pubertal age.

Patients and methods

In total, 15,822 boys and girls answered questionnaires half-yearly with information on pubertal development: age at menarche, first ejaculation, voice break, Tanner stages, axillary hair, and acne. Birth weight and gestational age were used to calculate birth weight Z-scores. Changes in infant weight Z-score from 0 to 5, 5 to 12, and 0 to 12 months were estimated. We estimated the mean monthly difference in timing of puberty between children born small-for-gestational age (SGA) and large-for-gestational age (LGA) with children born appropriate-for-gestational age (AGA) as reference. We further investigated whether increasing infant weight Z-scores were associated with age at attaining indicators of pubertal development.

Results

Girls born SGA reached all pubertal markers at an earlier mean age than girls born AGA, as indicated by mean age differences below zero (eg, age at menarche: −2.3 months, 95% CI: −3.4, −1.2), except for breast development. Girls born LGA reached pubertal markers later than girls born AGA (eg, age at menarche: 1.7 months, 95% CI 0.5, 2.9). Boys born SGA and LGA achieved puberty earlier than boys born AGA, though with CIs crossing zero (eg, age at voice break for SGA: −0.7 months, 95% CI −2.1, 0.7 and for LGA: −0.7 months, 95% CI −2.1, 0.8). A 1-unit increase in weight Z-score from 0 to 12 months was associated with a mean age difference of −1.7 to −0.3 months for pubertal development in both sexes.

Conclusion

Small size at birth and rapid infant growth were associated with early pubertal age, most consistent and pronounced in girls.

Keywords:

• puberty
• pubertal development
• tanner stages
• birth weight

Acknowledgment

This work was supported by the Danish Council for Independent Research [DFF 4183-00152 and 6166-00023]. The Danish Council for Independent Research was not involved in any stages from study design to submission of the paper.

The Danish National Birth Cohort was established with a significant grant from the Danish National Research Foundation. Additional support was obtained from the Danish Regional Committees, the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Health Foundation, and other minor grants. The DNBC Biobank has been supported by the Novo Nordisk Foundation and the Lundbeck Foundation.

Follow-up of mothers and children has been supported by the Danish Medical Research Council (SSVF 0646, 271-08-0839/06-066023, O602-01042B, 0602-02738B), the Lundbeck Foundation (195/04, R100-A9193), The Innovation Fund Denmark 0603-00294B (09-067124), the Nordea Foundation (02-2013-2014), Aarhus Ideas (AU R9-A959-13-S804), University of Copenhagen Strategic Grant (IFSV 2012), and the Danish Council for Independent Research (DFF – 4183-00594 and DFF - 4183-00152).

Abbreviations

AGA, appropriate-for-gestational age; BMI, body mass index; DNBC, The Danish National Birth Cohort; FGR, fetal growth restriction; HPG axis, hypothalamic–pituitary–gonadal axis; LGA, large-for-gestational age; SGA, small-for-gestational age.

Data availability

The dataset analyzed in the study is not publicly available due to national data security legislation on sensitive personal data.

Ethics approval and informed consent

The study was approved by the Steering Committee of the DNBC (2017-06). Data in DNBC and The Puberty Cohort were registered by the Danish Data Protection Agency (journal number 2012-41-0379 and 2015-57-0002). When the DNBC was established, the Committee on Biomedical Research Ethics approved the data collection ((KF) 01-471/94). Written consent was obtained from all women at recruitment.

Disclosure

The authors report no conflicts of interest in this work.