Parental infertility and sexual maturation in children

Parental time to pregnancy, medically assisted reproduction and pubertal development in boys and girls

STUDY QUESTION

Does parental fertility, measured by time to pregnancy (TTP), or use of medically assisted reproduction (MAR) affect pubertal development in the offspring?

SUMMARY ANSWER

Neither TTP nor type of MAR treatment had clinically relevant implications for mean age at achieving individual pubertal milestones or overall timing of puberty in boys and girls.

WHAT IS KNOWN ALREADY

Parental TTP and MAR have been associated with impaired semen quality in adult sons. Timing of puberty reflects earlier signals of reproductive health, but it remains unclear whether parental fertility or MAR affects pubertal development, especially in the growing generation of children conceived by IVF or ICSI.

STUDY DESIGN, SIZE, DURATION

In this study, 15 819 children born by mothers in the Danish National Birth Cohort from 2000 to 2003 participated in a nationwide puberty cohort (participation rate = 70%). Parental TTP and use of MAR were reported by mothers in early pregnancy and children’s pubertal development data was self-recorded in web-based questionnaires from 11 years of age and 6 monthly throughout puberty (2012–2018).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Pubertal development in children (of planned pregnancies, n = 13 285) born by untreated subfecund (TTP: 6–12 months) (n =2038), untreated severely subfeund (TTP: >12 months) (n = 1242), treated subfecund (n = 230) and treated severely subfecund (n = 1234) parents were compared to children born to more fertile parents (TTP: ≤5 months). We estimated mean monthly differences in mean age at achieving individual pubertal milestones (i.e. age at menarche, voice break, first ejaculation and Tanner stages 2, 3, 4 and 5 for breast or genital development and pubic hair growth) and a combined indicator of timing of puberty. Further, we compared mean age at achieving the individual pubertal milestones in children born by use of IVF or ICSI (n = 480) with children born by controlled ovarian stimulation or ovulation induction with or without intrauterine insemination (n = 902).

MAIN RESULTS AND THE ROLE OF CHANCE

We found tendencies towards slightly later mean age at male pubertal timing and slightly earlier mean age at female pubertal timing among children born by untreated subfecund, treated subfecund, untreated severely subfecund and treated severely subfecund parents. There were no specific patterns with increasing TTP, use of MAR nor type of MAR treatment, and the magnitude of the mean differences for individual milestones and overall timing of puberty were small, i.e. 0.9 months (95% CI: −1.0; 2.8) for first ejaculation and −0.5 months (95% CI: −2.0; 1.0) months for age at menarche in boys and girls, respectively, born by treated severely subfecund parents when compared with children born by more fertile parents.

LIMITATIONS, REASONS FOR CAUTION

Non-differential misclassification of the self-reported information on parental TTP and pubertal development in the offspring may serve as an alternative explanation of the findings, possibly biasing the estimates towards the null. The information on pubertal development was collected from around 11 years of age and onwards.

WIDER IMPLICATIONS OF THE FINDINGS

This study adds to the growing body of literature suggesting only limited harmful effects of parental subfecundity and MAR on offspring’s long-term growth and development.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Danish Council for Independent Research [DFF 4183-00152]; and the Faculty of Health at Aarhus University. The authors have no financial relationships or competing interests to disclose.

Timing of puberty in boys and girls: A population-based study

BACKGROUND

A secular trend towards earlier puberty has been observed in girls, while a similar trend has been more uncertain in boys. We estimated current ages at pubertal development in both boys and girls.

METHODS

In this population-based cohort study, 14 759 of 22 439 invited boys and girls born from 2000 to 2003 in the Danish National Birth Cohort gave half-yearly self-reported information on puberty from the age of 11.5 years and throughout puberty. This late start of follow-up limits the estimation of age at onset of puberty but not later pubertal milestones. We estimated mean age at attaining the following pubertal milestones in years with 95% confidence intervals (CI): age at menarche, voice break, first ejaculation of semen and Tanner stages for pubic hair development and breast development or genital development. Further, the difference in mean age at menarche between mothers and daughters was estimated.

RESULTS

In boys, voice break occurred at 13.1 (95% CI 13.0, 13.1) years, first ejaculation of semen occurred at 13.4 (95% CI 13.3, 13.4) years, and Tanner Genital Stage 5 occurred at 15.6 (95% CI 15.5, 15.6) years. In girls, age at menarche occurred at 13.0 (95% CI 13.0, 13.1) years and Tanner Breast Stage 5 occurred at 15.8 (95% CI 15.7, 15.9) years. Daughters had menarche 3.6 (95% CI 3.1, 4.2) months earlier than their mothers had.

CONCLUSION

These data indicate that age at menarche has declined and to some extent support a decline in age at attaining other markers of pubertal development among boys.

Is age at puberty associated with semen quality and reproductive hormones in young adult life?

The evidence is scarce on the association between age at puberty and semen quality. A cohort of 320 Danish men aged 18-21 years enrolled in the "Healthy Habits for Two" birth cohort provided self-reported data on pubertal indicators and delivered semen and blood samples. The results indicated an association between older age at pubertal development and lower semen quality and altered reproductive hormones concentrations as measured in young adult life. Men who had their first nocturnal emission, start of pubic hair growth and first voice break episode when older than 15 years had 37.0%, 45.0% and 32.7% lower sperm concentration; 37.8%, 44.2% and 29.1% lower total sperm count; 7.4%, 13.4% and 15.3% lower testosterone concentration; and 21.3%, 1.5% and 3.7% lower inhibin B concentration, respectively, compared with the men who were younger than 13 years at their first pubertal indicators. Only few of the results were statistically significant, but similar tendencies were seen in several of the reproductive parameters suggesting an association between the timing of pubertal development and reproductive health later in life.

Perceptual analysis of adolescents' vocal stability during different phonation tasks

BACKGROUND

Quality and frequency variability of adolescents' voice, during puberty, in different phonation tasks.

AIM

To analyze the vocal stability of adolescents in three different phonation tasks using a voice perceptual analysis.

METHOD

Participants were male students (n = 46 individuals), ranging in age from 13 to 15 years, from a public school in Campinas--SP. Voice samples were recorded using a digital recorder in three different tasks: speaking a sustained vowel /a/, counting from one to ten, and reading. Three voice specialists evaluated stability by means of voice perceptual analysis. For the voice samples that were considered unstable, the Analogical Visual Scale (AVS) of 10 cm was used to estimate the instability level, where zero means absence of instability and ten refers to maximum instability.

RESULTS

78.3% of the adolescents presented vocal instability when speaking the sustained vowel, varying from one to nine in the AVS. Only one adolescent presented unstable voice when counting numbers (level = 1). Vocal instability was not observed during reading for any of the participants. Vocal stability varied significantly among phonation tasks and adolescents showed greater instability during the sustained vowel (p<0.0001; g.l = 2).

CONCLUSION

Counting numbers and reading do not detect vocal instability; the production of a sustained vowel demonstrated to be a better task.