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

LIN 28B expression is downregulated in mature spermatozoa of oligozoospermic men and associates with genetic variants previously linked to pubertal onset

LIN28B is an RNA-binding protein that acts as a post-transcriptional regulator of genes involved in developmental timing and self-renewal through its interaction with let-7 miRNAs. Large-scale genomic studies have strongly implicated SNPs in LIN28B with male puberty timing. In addition, the occurrence of late puberty is linked to diminished semen quality in adult life. Therefore, we aimed to study the association of puberty-linked LIN28B genetic variants with semen parameters, reproductive hormones and the spermatozoa expression of the LIN28B/Let-7 axis in idiopathic oligozoospermic men. One hundred and eleven oligozoospermic (cases) and 258 men with normal sperm concentration (controls) were genotyped for five LIN28B SNPs (rs7759938, rs395962, rs314268, rs314277 and rs314280). The abundance of the LIN28B transcript, let-7a and let-7c miRNAs were measured by qRT-PCR in RNA isolated from purified sperm. Serum blood samples were analysed for reproductive hormones. Lower abundance of the LIN28B transcript and higher expression of let-7c were observed in cases (P < 0.001). Furthermore, rs395962_T was associated with a reduced abundance of the LIN28B transcript in cases (dominant: P = 0.032). On the other side, we observed a positive association of rs314277_A (Additive: P = 0.024), rs7759938_C (dominant: P = 0.025) and rs314280_A (dominant: P = 0.024) with total testosterone levels in cases. The decreased transcript abundance of LIN28B in sperm of idiopathic oligozoospermic men and its association with SNPs known to affect the onset of puberty and total testosterone levels suggests a role for LIN28B in the primary impairment of spermatogenesis through its expression in early germ cells or regulating the testicular biosynthesis of testosterone at a central level. Therefore, our results provide a potential mechanistic link between the regulation of pubertal timing and adult testicular function.

Atopic dermatitis in childhood and pubertal development: A nationwide cohort study

Background

Atopic dermatitis (AD) might delay puberty, but research is lacking.

Objective

To investigate the association between AD and puberty.

Methods

A subcohort within the Danish National Birth Cohort includes children born between 2000 and 2003, with mothers reporting doctor-diagnosed AD at 6 months, 18 months, and 7 years old. The National Patient Registry identified hospital-diagnosed AD. From 11 years, the children give half-yearly information on pubertal development. We estimated the mean age difference in months at attaining Tanner stages 1 to 5 and the development of axillary hair, acne, first ejaculation, voice break, and age at menarche, using an interval-censored regression model.

Results

In total, 15,534 children participated, 21.5% had self-reported doctor-diagnosed AD and 0.7% had hospital-diagnosed AD. For girls with self-reported doctor-diagnosed AD, the average age difference at reaching all pubertal milestones was 0.0 months (95% confidence interval [CI]: -0.8; 0.8), and for hospital-diagnosed AD, it was -0.3 months (95% CI: -5.4; 4.8). For boys, the average age difference was 0.1 months (95% CI: -0.6; 0.9) and -0.3 months (95% CI: -3.6; 3.0), respectively.

Limitations

No information on treatment was available. Missing data on covariates (<5%) were not addressed.

Conclusion

No association was found between AD and puberty in either girls or boys.

Characteristics of Puberty in a Population-Based Sample of Danish Adolescents

PURPOSE

To describe the duration, timing, tempo, and synchronicity of puberty, as well as the correlation between timing and tempo of puberty.

METHODS

Overall, 15,819 of 22,439 invited children participated in the Puberty Cohort within the Danish National Birth Cohort. Participants completed a web-based questionnaire every 6 months through maturation with questions on current pubertal status. Girls reported current Tanner stage of breast and pubic hair development, and timing of menarche. Boys reported current Tanner stage of genital and pubic hair development, timing of first ejaculation, and vocal changes. While accounting for this interval-censored puberty information, we estimated the duration of puberty. Then, we used a nonlinear mixed effect growth model to estimate timing, tempo, synchronicity of puberty, and correlation between timing and tempo of puberty.

RESULTS

In girls, the average duration of breast development was longer, whereas the average tempo was slower than pubic hair development. The average timing of breast development was earlier than the average timing of pubic hair development. The majority of girls had asynchronous puberty. In boys, the average duration was longer and average tempo slower for genital than pubic hair development. The average timing of genital and pubic hair development were comparable; hence, the majority had synchronous pubertal development. Adolescents who had earlier timing also tended to have a faster tempo.

DISCUSSION

Being one of the largest puberty cohorts worldwide, these unique contemporary data can help physicians, parents, and children to understand and anticipate expected progression through pubertal development.

Timing of puberty in relation to semen characteristics, testicular volume, and reproductive hormones: a cohort study

OBJECTIVE

To investigate whether the timing of puberty is associated with semen characteristics, testicular volume, and reproductive hormone levels.

DESIGN

Cohort study.

SETTING

Not applicable.

PATIENTS

The Danish National Birth Cohort and its subcohort, the Fetal Programming of Semen Quality cohort of 1,058 young men.

INTERVENTION(S)

Self-reported information on the timing (younger, same age, older than peers) of the pubertal markers: voice break (primary exposure), pubic hair growth, regular shaving, and axillary hair growth.

MAIN OUTCOME MEASURES(S)

We estimated the relative differences with 95% confidence intervals for semen characteristics (semen volume, sperm concentration, total sperm count, sperm motility, percentage of morphologically normal spermatozoa), testicular volume, and reproductive hormones (follicle stimulating hormone [FSH], luteinizing hormone, sex hormone-binding globulin [SHBG], testosterone, estradiol, and free androgen index [FAI]) obtained at a median age of 19.2 years according to timing of pubertal development.

RESULT(S)

Compared with men reporting voice break "same age as peers," men reporting voice break "older than peers" tended to have lower total sperm count (-12% [-25%, 4%]) and lower percent morphologically normal spermatozoa (-10% [-20%, 2%]), whereas men reporting voice break "younger than peers" tended to have a lower proportion of nonprogressive and immotile spermatozoa (-6% [-13%, 1%]) and larger testicular volume (7% [1%, 13%]). The pattern was less consistent for the other pubertal markers. For reproductive hormones, voice break "older than peers" tended to have higher FSH levels (24% [-1%, 55%]), higher SHBG levels (7% [0, 15%]), lower estradiol levels (-14% [-23%, -5%]), and lower FAI (-8% [-14%, -1%]), whereas voice break "younger than peers" tended to have higher luteinizing hormone levels (4% [-2%, 11%]), higher testosterone levels (5% [0%, 11%]), higher estradiol levels (17% [6%, 29%]), and higher FAI (4% [-2%, 11%]). When the categorical pubertal markers were analyzed as a linear term to assess dose dependence, older age at pubertal development was associated with higher FSH levels, higher SHBG levels, lower testosterone levels, lower estradiol levels, and lower FAI for most pubertal markers.

CONCLUSION(S)

These results lend weak support to the hypothesis that older age at pubertal development is associated with markers of reduced male fecundity, especially reproductive hormone levels, although associations with semen characteristics and testicular volume were statistically insignificant.

Maternal intake of folate and folic acid during pregnancy and pubertal timing in girls and boys: A population-based cohort study

BACKGROUND

Folate is essential for normal foetal development as it plays an important role for gene expression during different periods of foetal development. Thus, prenatal exposure to folate may have a programming effect on pubertal timing.

OBJECTIVES

To study the association between maternal intake of folate during pregnancy and pubertal timing in girls and boys.

METHODS

We studied 6585 girls and 6326 boys from a Danish population-based Puberty Cohort, 2000-2021. Information on maternal intake of folate from diet and folic acid from supplements was obtained from a food-frequency questionnaire in mid-pregnancy, and total folate was calculated as dietary folate equivalents. Information on age at menarche in girls, age at first ejaculation and voice break in boys, and Tanner stages, acne and axillary hair in both girls and boys was obtained every 6 months throughout puberty. We estimated mean monthly differences according to exposure groups for each pubertal milestone in addition to a combined estimate for the average age at attaining all pubertal milestones using multivariable interval-censored regression models. Total folate was analysed in quintiles, continuous and as restricted cubic splines.

RESULTS

Maternal intake of total folate in mid-pregnancy was not associated with pubertal timing in girls (combined estimate for overall pubertal timing per standard deviation (SD 325 μg/day) decrease in maternal intake of total folate: -0.14 months (95% confidence interval [CI] -0.51, 0.22)). Boys had slightly later overall pubertal timing per standard deviation (SD 325 μg/day) decrease in maternal intake of total folate (combined estimate: 0.40 months, 95% CI 0.01, 0.72). Spline plots supported these findings.

CONCLUSIONS

Prenatal exposure to low maternal intake of total folate in mid-pregnancy was not associated with pubertal timing in girls but associated with slightly later pubertal timing in boys. This minor delay is likely not of clinical importance.

Maternal age at menarche and reproductive health in young adult men: a cohort study

STUDY QUESTION

Is maternal age at menarche associated with reproductive health in sons measured by semen quality, testes volume and reproductive hormone levels?

SUMMARY ANSWER

Later maternal age at menarche was associated with impaired semen characteristics, lower testes volume and altered levels of reproductive hormones, while earlier maternal age at menarche was not strongly associated with reproductive outcomes in sons.

WHAT IS KNOWN ALREADY

Both earlier and later maternal age at menarche may be associated with altered male reproductive health outcomes. This is the first study to investigate the potential association between maternal age at menarche and semen quality, testes volume and reproductive hormone levels in sons.

STUDY DESIGN, SIZE, DURATION

In this population-based cohort study, we used data from the Fetal Programming of Semen Quality Cohort nested within the Danish National Birth Cohort. In total, 5697 sons born in 1998-2000 were invited to participate in the cohort in 2017-2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In total, 1043 (18% of the invited) young men with information on maternal age at menarche provided a semen and blood sample, measured their testes volume, and filled in a questionnaire on health behavior and pubertal development. Maternal age at menarche was reported by the mothers during pregnancy and examined categorically (as earlier, at the same time or later than their peers), continuously and modeled as splines. We estimated relative percentage differences in the reproductive outcomes using negative binomial regression models. Further, we did a mediation analysis to investigate the potential mediating role of timing of the sons' pubertal development.

MAIN RESULTS AND THE ROLE OF CHANCE

Sons whose mothers had age at menarche later than peers had 15% lower (95% CI: -27%; 0%) sperm concentration, 14% lower (95% CI: -28%; 1%) total sperm count, 7% higher (95% CI: 0%; 14%) proportion of nonprogressive or immotile spermatozoa, 6% lower (95% CI: -11%; 0%) testes volume, 6% lower (95% CI: -12%; 1%) luteinizing hormone, 6% lower (95% CI: -12%; 1%) sex hormone-binding globulin and 5% lower (95% CI: -9%; 0%) testosterone levels compared with sons whose mothers had age at menarche at the same time as peers. Our study did not suggest that earlier maternal age at menarche was strongly associated with semen quality, testes volume or reproductive hormones in sons. However, the spline analyses indicated a potential inverted U-shaped association for sperm concentration and testes volume, and levels of sex hormone-binding globulin and testosterone. We found no strong evidence of mediation by timing of the sons' own pubertal development.

LIMITATIONS, REASONS FOR CAUTION

There was a rather low participation rate in the Fetal Programming of Semen Quality Cohort and we tried to counter it by applying selection weights. Maternal age at menarche was recalled during pregnancy, which may introduce misclassification, most likely nondifferential. Inaccuracy of the sons' recalled pubertal development years after the event may result in underestimation of the possible mediating role of pubertal timing.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings may represent a degree of shared heritability of reproductive health or be a result of an underlying epigenetic profile or unknown shared environmental, cultural or dietary exposure, causing both altered age at menarche and impaired reproductive health outcomes in sons. However, the exact mechanism for the investigated association remains unknown.

STUDY FUNDING/COMPETING INTEREST(S)

This article is part of the ReproUnion collaborative study, cofinanced by the European Union, Intereg V ÖKS (20200407). The FEPOS project was further funded by the Lundbeck Foundation (R170-2014-855), the Capital Region of Denmark, Medical doctor Sofus Carl Emil Friis and spouse Olga Doris Friis's Grant, Axel Muusfeldt's Foundation (2016-491), A.P. Møller Foundation (16-37), the Health Foundation and Dagmar Marshall's Fond. Additionally, this study received funding from Aarhus University. There are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Urological and Gynaecological Considerations for the Use of Gonadotropin-releasing Hormone Analogues in Transgender and Nonbinary Adolescents: A Narrative Review

CONTEXT

Gonadotropin-releasing hormone analogues (GnRHAs) delay the progression of puberty in transgender and nonbinary (TGNB) adolescents and reduce the impact of dysphoria due to ongoing physical development. The intervention remains contentious despite growing evidence to support this practice.

OBJECTIVE

To stimulate discussion on this topical issue in the urological and gynaecological community given potential ramifications for future fertility, physical development, and options for gender affirmation surgery (GAS).

EVIDENCE ACQUISITION

We conducted searches of the MEDLINE (from 1946) and Embase (from 1974) databases for the benefits and potential challenges of hormone blockade in TGNB adolescents on February 1, 2022. Evidence with a primary focus on clinical issues of interest to urologists and gynaecologists was objectively synthesised and reported.

EVIDENCE SYNTHESIS

The onset of puberty represents a period of distress for TGNB adolescents as secondary sexual characteristics develop. GnRHAs are prescribed to inhibit sex hormone production, but the decision to treat should be balanced against the known (and unknown) adverse effects. Fertility preservation is more likely to be successful if GnRHA treatment is delayed for as long as possible. Some adolescents may decide to stop GnRHA use to harvest spermatozoa or oocytes before starting gender-affirming hormone treatment. Transfeminine individuals should consider that options for genital GAS may become more limited, as vaginoplasty with penile skin inversion requires an adequate stretched penile length. Transmasculine individuals may no longer require chest reconstruction for breast development.

CONCLUSIONS

Offers of GnRHA treatment to TGNB adolescents should be balanced by careful preparation and counselling. Urologists and gynaecologists can complement the expertise of specialist psychosocial and adolescent endocrinology teams, and should be involved early in and throughout the treatment pathway to maximise future functional and surgical outcomes.

PATIENT SUMMARY

Puberty blockers for transgender and nonbinary adolescents have benefits, but timing is important to preserve fertility and surgical options.

Semen quality and reproductive hormones in sons of subfertile couples: a cohort study

OBJECTIVE

To study the associations between parental subfecundity, assessed by time to pregnancy and use of medically-assisted reproduction, and reproductive health of young men.

DESIGN

Cohort study.

SETTING

Denmark.

PATIENT(S)

A total of 1,058 men in the Fetal Programming of Semen quality cohort, a subcohort of the Danish National Birth Cohort.

INTERVENTION(S)

From 2017-2019, men were recruited and provided semen and blood samples. Information on parental time to pregnancy and use of medically-assisted reproduction (including type of treatment) as well as demographic, health, and lifestyle factors were available. We estimated the crude and adjusted relative percentage differences with 95% confidence intervals (CIs) in the outcomes according to time to pregnancy and use of medically-assisted reproduction, using multiple adjusted negative binomial regression analysis.

MAIN OUTCOME MEASURE(S)

Semen characteristics (semen volume, sperm concentration, total sperm count, sperm motility, and morphology), testicular volume, and reproductive hormone levels (follicle stimulating hormone, luteinizing hormone, testosterone, estradiol, sex hormone-binding globulin, and free androgen index).

RESULT(S)

Overall, semen quality and levels of reproductive hormones were not lower among sons of subfecund parents reporting a time to pregnancy >6 months or use of intrauterine insemination. Sons conceived after in vitro fertilization or intracytoplasmic sperm injection, had a higher semen concentration (29%; 95% CI, -7%-79%) and a higher percentage of sperm with normal morphology (20%; 95% CI, -8%-56%), but with 95% CI overlapping the null. Moreover, these sons had slightly higher estradiol levels (30%; 95% CI, 7%-57%). The absolute differences seen were small, and the clinical significance of these differences are unknown.

CONCLUSION(S)

We found no major difference in semen quality or reproductive hormones in sons conceived by subfertile couples or with the use of medically-assisted reproduction.

Timing of Pubertal Development in Boys and Girls With Congenital Heart Defects: A Nationwide Cohort Study

Background

Children with congenital heart defects (CHD) have an increased risk of developmental delay. It remains sparsely investigated if these patients also have a delayed pubertal development. In this nationwide cohort study, we evaluated if CHD was associated with timing of puberty using longitudinally collected data on pubertal milestones.

Methods and Results

We used data from the Danish nationwide Puberty Cohort. Information on CHD was obtained from the Danish National Patient Register. Information on pubertal development was obtained from 15 780 children through questionnaires answered half‐yearly from 11 years until 18 years or full maturity. Using a multivariable regression model for censored time‐to‐event data, mean difference in age at attaining each pubertal milestone was estimated, including a combined pubertal marker. Compared with children without CHD, analyses were performed for both CHD overall and subdivided into simple and complex CHD. In a subanalysis, analyses were repeated in children born at term. In total, 137 children (62 boys and 75 girls) had a CHD diagnosis. Overall, no difference in age at pubertal timing was observed for children with CHD compared with unaffected children. The average differences were small for both boys (1.6 [95% CI, −2.6 to 5.7] months) and girls (1.0 [95% CI, −2.5 to 4.4] months). The same differences were observed when subdividing into simple or complex CHD and when restricting to children born at term.

Conclusions

We found no association between CHD and pubertal timing. For the group of children with complex CHD, we were unable to exclude a later pubertal timing.

Toxic and Teratogenic Effects of Prenatal Alcohol Exposure on Fetal Development, Adolescence, and Adulthood

Prenatal alcohol exposure (PAE) can have immediate and long-lasting toxic and teratogenic effects on an individual’s development and health. As a toxicant, alcohol can lead to a variety of physical and neurological anomalies in the fetus that can lead to behavioral and other impairments which may last a lifetime. Recent studies have focused on identifying mechanisms that mediate the immediate teratogenic effects of alcohol on fetal development and mechanisms that facilitate the persistent toxic effects of alcohol on health and predisposition to disease later in life. This review focuses on the contribution of epigenetic modifications and intercellular transporters like extracellular vesicles to the toxicity of PAE and to immediate and long-term consequences on an individual’s health and risk of disease.

Analysis of the screening results of 24040 potential sperm donors in a human sperm bank in Henan Province, China: a 14-year retrospective cohort study

STUDY QUESTION

Is there a relation between the characteristics of potential sperm donors and the acceptance rate of these potential donors?

SUMMARY ANSWER

A relatively higher acceptance rate was observed for potential sperm donors who were aged ≤ 35 years, were married, had children, and who had received higher education, and acceptance rates were also higher during spring and winter than summer and autumn.

WHAT IS KNOWN ALREADY

Recruiting donors to a sperm bank program is difficult and slow owing to the high rates of rejection and dropout.

STUDY DESIGN, SIZE, DURATION

A total of 24040 potential sperm donors were screened by the Henan Human Sperm Bank from 2006 to 2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Potential sperm donors were recruited using the following baseline requirement: height of 168 cm or taller; age 22-45 years; currently attending or had graduated from high school or above. Men who met the criteria for age, height, and education level were invited for semen quality screening. The acceptable criteria for semen samples included liquefaction time < 60min, volume ≥ 2mL, sperm concentration ≥ 60 × 106/mL, progressive motility ≥ 60%, post-thaw motility ≥ 40%, pre-freezing total motile sperm per vial > 30 × 106/mL, post-thaw total motile sperm per vial > 12 × 106/mL, and freeze-thaw survival rate ≥ 60%. Any potential sperm donors meeting the minimum criteria for acceptable semen quality on two consecutive semen samples were scheduled for clinical assessment, physical examination, and laboratory tests. The reasons for sperm donor rejection were analyzed. The characteristics of accepted and rejected donors were compared using the chi-square test, and multivariate logistic regression analyses were conducted to identify factors associated with the acceptance rate of potential sperm donors and the positive rate of sexually transmitted diseases (STDs).

MAIN RESULTS AND THE ROLE OF CHANCE

Only 23.38% (5620/24040) of potential sperm donors were accepted. The top four reasons for rejection were suboptimal semen quality (90.27%), STDs (6.26%), dropped out (2.65%), and chromosomal abnormalities (0.35%). The most common reason for the rejection of donors with an STD was a positive test for mycoplasmas (49.05%), followed by hepatitis B virus (27.56%), Chlamydia trachomatis (4.68%), and Escherichia coli (3.03%). n this study, the acceptance rate for men aged ≤ 35 years was significantly higher than that for men aged >35 years (P < 0.05). The acceptance rates were also significantly higher for men with a higher education than for men with lower education, married men than unmarried men, and men with children than men without children (P < 0.05). Moreover, acceptance rates were significantly higher during spring and winter than during summer (P <0.05) but were not significantly higher during autumn than during summer (P >0.05).

LIMITATIONS, REASONS FOR CAUTION

This study was not performed to analyze the effect of lifestyle habits, such as alcohol consumption and cigarette smoking, on the acceptance rate of potential sperm donors.

WIDER IMPLICATIONS OF THE FINDINGS

Only a small proportion of potential sperm donors were accepted in this anonymous sperm donor program. New strategies for sperm donor recruitment may be required to improve the acceptance rate. In the future, we may have to target potential sperm donors who are aged ≤ 35 years and who received higher education in order to improve the acceptance rate.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Joint Construction Project of Henan Medical Science and Technology Research Plan under grant number LHGJ20190389. The authors report no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Maternal pre-pregnancy obesity and timing of puberty in sons and daughters: a population-based cohort study

Background

In many countries, an increased prevalence of obesity in pregnancy has coincided with a declining pubertal age. We aimed to explore the potential effect of maternal pre-pregnancy overweight and obesity on timing of puberty in sons and daughters.

Methods

Between 2012 and 2018, 15 819 of 22 439 invited children from the Danish National Birth Cohort, born 2000–03, provided half-yearly information from the age of 11 years on the pubertal milestones: Tanner stages, voice break, first ejaculation, menarche, acne and axillary hair. We estimated adjusted mean monthly differences (with 95% confidence intervals) in age at attaining the pubertal milestones for children exposed to maternal pre-pregnancy obesity [body mass index (BMI) ≥30.0 kg/m²] or overweight (BMI 25.0 to 29.9 kg/m²) with normal weight (BMI 18.5 to 24.9 kg/m²) as reference. In mediation analysis, we explored whether childhood BMI at age 7 years mediated the associations.

Results

Maternal pre-pregnancy obesity was associated with earlier age at attaining most pubertal milestones in sons, and pre-pregnancy overweight and obesity were associated with earlier age at attaining all pubertal milestones in daughters. When combining all pubertal milestones, pre-pregnancy obesity [sons: −1.5 (−2.5, −0.4) months; daughters: −3.2 (−4.2, −2.1) months] and overweight [daughters only: −2.6 (−3.3, −1.8) months] were associated with earlier timing of puberty. The associations in sons were completely mediated by higher childhood BMI and partly so in daughters.

Conclusions

Maternal pre-pregnancy obesity appears to lower timing of puberty through childhood obesity in sons and mainly through other mechanisms in daughters.

The First Ejaculation: A Male Pubertal Milestone Comparable to Menarche?

Boys experience their first ejaculation (thorarche) during adolescence, but this event is often overlooked as a milestone in male adolescent development. The purpose of this article is to draw attention to thorarche and consider it in comparison with the female milestone of menarche. A critical analysis is provided of how thorarche has been interpreted to date and the complexities in construing thorarche from a biological perspective are outlined. Despite potential tenability of characterizing thorarche as a comparable milestone to menarche, two particular points challenge this notion: (a) While thorarche may befall the boy involuntarily, it may also be induced by the boy's own will; and (b) Thorarche occurs concomitantly with (pubertal) orgasmarche and has an innate connection with sexuality. The answer to the title question remains contentious, but open topics for future research are noted throughout the article as essential steps towards attaining a better understanding of thorarche.

Alcohol intake during pregnancy and timing of puberty in sons and daughters: A nationwide cohort study

We explored whether maternal alcohol intake in early pregnancy is associated with pubertal timing in sons and daughters. In total, 15,819 children, born 2000-2003 within the Danish National Birth Cohort, gave half-yearly, self-reported information on pubertal development (Tanner stages, voice break, first ejaculation, menarche, acne, and axillary hair) from 11 years during 2012-2018. Information on maternal average alcohol intake in first trimester and binge drinking episodes (intake of ≥5 drinks on the same occasion) in first trimester was self-reported by mothers during pregnancy. Average alcohol intake of 5+ weekly drinks in first trimester was not associated with pubertal timing in sons (with no alcohol intake as the reference). A tendency towards earlier pubertal timing was observed in daughters (-2.0 (95 % confidence interval: -4.2, 0.3) months) when combining the estimates for all pubertal milestones. Binge drinking was not associated with pubertal timing in neither sons nor daughters.

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.