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 polycystic ovarian syndrome and pubertal development in daughters and sons: a population-based cohort study.

STUDY QUESTION: Does maternal polycystic ovarian syndrome (PCOS) affect the timing of pubertal development in daughters and sons? SUMMARY ANSWER: Maternal PCOS was associated with earlier adrenarche in daughters. WHAT IS KNOWN ALREADY: Female adolescents with PCOS often experience earlier adrenarche compared to adolescents without PCOS, due to hyperandrogenism. Likewise, they usually have hyperandrogenism during pregnancy, which might potentially affect the development of the foetus, including its future reproductive health. STUDY DESIGN, SIZE, DURATION: In this population-based cohort study, we included 15 596 mothers-child pairs from the Danish National Birth Cohort (DNBC) Puberty Cohort, who were followed from foetal life until full sexual maturation or 18 years of age. PARTICIPANTS/MATERIALS, SETTING, METHODS: Using register-based and self-reported information on maternal PCOS and menstrual irregularities, collected during pregnancy, we categorized the mothers as having PCOS (n = 251), oligomenorhoea (n = 134), 'other menstrual irregularities' (n = 2411) or no menstrual abnormalities (reference group, n = 12 800). The children provided self-reported information on pubertal development every 6 months from the age of 11 years. The main outcome measures were adjusted mean age differences (in months) at attaining several individual pubertal milestones using an interval-censored regression model, as well as the average difference in age at attaining all pubertal milestones combined into a single estimate using Huber-White robust variance estimation. MAIN RESULTS AND THE ROLE OF CHANCE: We found that maternal PCOS was associated with an accelerated pubertal development in daughters with an overall average difference of -3.3 (95% CI: -6.3; -0.4) months based on all pubertal milestones compared to the reference group. When further looking into the average difference for adrenarche only (pubarche, axillary hair and acne), the average difference was -5.4 (95% CI: -8.7; -2.1) months compared to the reference group; whereas thelarche and menarche did not occur earlier in daughters of mothers with PCOS (average difference: -0.8 (95% CI: -3.9; 2.4) months). Oligomenorrhoea and 'other menstrual irregularities' were not associated with pubertal development in daughters. Neither PCOS, oligomenorrhoea nor 'other menstrual irregularities' were associated with pubertal development in sons. LIMITATIONS, REASONS FOR CAUTION: We expect some degree of non-differential misclassification of maternal PCOS and menstrual irregularities as well as pubertal development in the children. WIDER IMPLICATIONS OF THE FINDINGS: Maternal PCOS might accelerate adrenarche in daughters. Whether this is due to genetics, epigenetics or prenatal programming by hyperandrogenism in foetal life remains unsolved. The results from the present study can be generalized to Caucasian populations. STUDY FUNDING/COMPETING INTEREST(S): The study is funded by the Faculty of Health at Aarhus University. The authors have no financial relationships or competing interests to disclose. TRIAL REGISTRATION NUMBER: N/A.

Caesarean delivery and pubertal timing in boys and girls: A Danish population-based cohort study.

BACKGROUND: There is considerable public and scientific interest in the declining age of pubertal timing. Prenatal and postnatal stress has been proposed to relate with earlier pubertal timing, but it remains unknown whether intrapartum stress may affect pubertal timing as well. OBJECTIVE: This study aims to examine the potential effect of caesarean delivery on pubertal timing in boys and girls. METHODS: This study was based upon the nationwide Puberty Cohort nested within the Danish National Birth Cohort (DNBC) from 2000 to 2003. A total of 15,731 mother-child pairs with complete information on delivery mode and puberty were included in the main analysis. The delivery mode was categorised into non-instrumental vaginal delivery (reference), instrumental vaginal delivery, elective caesarean delivery before labour, emergency caesarean delivery during labour and un-specified caesarean delivery. Children's pubertal development were self-reported in web-based questionnaires from 11 years of age and every 6 months throughout puberty (2012-2019), including Tanner stages 2-5, menarche, voice break, first ejaculation, axillary hair growth and the onset of acne. Regression models for censored, normally distributed time-to-event data were used to estimate mean monthly differences in age at attaining the different pubertal milestones and the average of all these estimates for each sex (a combined indicator of pubertal timing). RESULTS: A total of 2810 participants were born by caesarean delivery (17.9%). Neither elective nor emergency caesarean delivery was associated with earlier age at achieving the pubertal milestones in boys or in girls. For the combined indicator, the mean age differences for elective caesarean delivery and emergency caesarean delivery were 0.1 (95% CI -1.1, 1.4) months and -0.7 (95% CI -2.0, 0.5) months in boys and 0.7 (95% CI -0.7, 2.0) and 0.2 (95% CI -1.3, 1.7) in girls. CONCLUSIONS: This study does not suggest a clinically important effect of caesarean delivery on children's pubertal timing.

The influence of parental age on timing of puberty: A study in the Danish National Birth Cohort.

Aims: Concerns have been raised about the potential negative biological effect of postponed parenthood upon the health of subsequent generations, including reproductive health. This study aimed to estimate if high parental age at birth was associated with accelerated pubertal timing in offspring. Methods: In this large-scale cohort 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 71%). Between 2012 and 2018, the children reported half-yearly information on pubertal status using web-based questionnaires from 11 years throughout puberty or 18 years of age. Information on parental age was drawn from nationwide registers. We estimated adjusted mean differences in months for age at attaining the pubertal milestones and pubertal timing overall between the pre-specified parental age groups: 20-29 (reference), 30-34 and advanced parental age groups (35-44 years for mothers and >35 years for fathers). Results: Overall, parental age at birth of the child was not associated with pubertal timing in daughters or sons. For sons of older fathers (>35 years), we observed indications towards slightly earlier pubertal timing in the range of 0.3-2.4 months for nearly all pubertal milestones, but all confidence intervals were wide, and many included the null. Conclusions: We found no strong association between parental age and timing of puberty, and we find it unlikely that the decreasing age in pubertal timing is a result of parental decision to delay childbearing.

Father Absence in Pregnancy or During Childhood and Pubertal Development in Girls and Boys: A Population-Based Cohort Study.

This cohort study, including 15,810 children born 2000-2003 in Denmark, aimed to investigate the association between father absence in pregnancy or during childhood and pubertal development in girls and boys. The children were followed from 11 years of age and throughout pubertal development. Mean age differences according to exposure groups were estimated for each pubertal marker separately and for a combined pubertal marker. The results suggested that father absence in pregnancy and during childhood was associated with earlier pubertal development in girls, and father absence from late childhood was associated with earlier pubertal development in boys. The paternal investment theory, the psychosocial acceleration theory and the energetics theory were explored, and did not seem to explain the observed associations.

Hypertensive disorders in pregnancy and timing of pubertal development in daughters and sons.

STUDY QUESTION: Do maternal hypertensive disorders affect pubertal development in daughters and sons? SUMMARY ANSWER: Pubertal development tended to occur earlier in daughters of mothers with 'preeclampsia, eclampsia or HELLP syndrome' (hemolysis, elevated liver enzymes and low blood platelets) or hypertension in pregnancy compared to daughters born of normotensive mothers. WHAT IS KNOWN ALREADY: The existing literature suggests some or no association between preeclampsia and pubertal development in daughters, but not in sons. None of the previous studies has investigated the possible association between other types of hypertensive disorders (hypertension, eclampsia or HELLP syndrome) and pubertal timing in children. STUDY DESIGN, SIZE, DURATION: Longitudinal cohort study consisting of 15 819 mother-child pairs with information on maternal hypertensive disorders collected during pregnancy and information on pubertal development collected half-yearly from the age of 11 years and until fully developed or 18 years of age. PARTICIPANTS/MATERIALS, SETTING, METHODS: Participants are children from the Puberty Cohort nested within the Danish National Birth Cohort. The exposure was register-based and self-reported information on maternal hypertensive disorders during pregnancy. The outcomes were children's self-reported information on pubertal development, including Tanner stage 1-5 (pubic hair (both daughters and sons) and breast development (daughters) or genital development (sons)), first menstrual bleeding (daughters) or first ejaculation (sons), voice break episode (sons), axillary hair development and acne occurrence (both daughters and sons). The main outcome was mean difference in age at attaining each pubertal milestone and a combined pubertal marker in children of mothers with hypertensive disorders in pregnancy (either hypertension (n = 490), 'preeclampsia, eclampsia or HELLP syndrome' (n = 419) or 'unspecific hypertensive disorders' (n = 334) with unexposed children as reference (n = 14 576)). MAIN RESULTS AND THE ROLE OF CHANCE: In daughters of mothers with 'preeclampsia, eclampsia or HELLP syndrome', we observed tendencies of earlier pubertal timing (combined marker: -2.0 (95% CI: -3.9; 0.0) months). In daughters of mothers with hypertension, several pubertal milestones tended to occur earlier than in daughters of normotensive mothers; however, all 95% CIs overlapped the null resulting in a combined pubertal marker of -1.0 (95% CI: -3.2; 1.1) months. In sons of mothers with any of the hypertensive disorders, we observed no difference in pubertal timing (combined markers: 'preeclampsia, eclampsia or HELLP syndrome': 0.1 (95% CI: -2.0; 2.1) months; hypertension: -0.6 (95% CI: -2.3; 1.1) months; 'unspecific hypertensive disorders': 0.2 (95% CI: -1.9; 2.2) months). LIMITATIONS, REASONS FOR CAUTION: The study is subject to non-differential misclassification of self-reported information on maternal hypertensive disorders in pregnancy and current pubertal status; possibly causing bias toward the null. WIDER IMPLICATIONS OF THE FINDINGS: Hypertensive disorders in pregnancy might accelerate pubertal timing in daughters; however, more studies are needed for causal conclusions. STUDY FUNDING/COMPETING INTEREST(S): The study was funded by the Faculty of Health at Aarhus University. The authors have no financial relationships or competing interests to disclose. TRIAL REGISTRATION NUMBER: N/A.

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.

Maternal Intake of Vitamin D Supplements during Pregnancy and Pubertal Timing in Children: A Population-Based Follow-Up Study.

Maternal vitamin D may be important for several organ systems in the offspring, including the reproductive system. In this population-based follow-up study of 12,991 Danish boys and girls born 2000-2003, we investigated if maternal intake of vitamin D supplements during pregnancy was associated with pubertal timing in boys and girls. Information on maternal intake of vitamin D supplements was obtained by self-report in mid-pregnancy. Self-reported information on the current status of various pubertal milestones was obtained every six months throughout puberty. Mean differences in months at attaining each pubertal milestone and an average estimate for the mean difference in attaining all pubertal milestones were estimated according to maternal intake of vitamin D supplements using multivariable interval-censored regression models. Lower maternal intake of vitamin D supplements was associated with later pubertal timing in boys. For the average estimate, boys had 0.5 months (95% CI 0.1; 0.9) later pubertal timing per 5 µg/day lower maternal vitamin D supplement intake. Maternal intake of vitamin D supplements was not associated with pubertal timing in girls. Spline plots and sensitivity analyses supported the findings. Whether the observed association with boys' pubertal timing translates into an increased risk of disease in adulthood is unknown.

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.

The estimated effect of season and vitamin D in the first trimester on pubertal timing in girls and boys: a cohort study and an instrumental variable analysis.

BACKGROUND: Season of birth has been associated with age at menarche. Maternal vitamin D levels in pregnancy may explain this effect. We investigated whether the season of first trimester or maternal 25-hydroxyvitamin D3 [25(OH)D3] levels were associated with pubertal timing in children. METHODS: We conducted a follow-up study of 15 819 children born in 2000-03 from the Puberty Cohort, nested in the Danish National Birth Cohort (DNBC). Mean differences in attaining numerous pubertal markers, including a combined estimate for the average age at attaining all pubertal markers, were estimated for low (November-April) relative to high (May-October) sunshine exposure season in the first trimester using multivariable interval-censored regression models. Moreover, we conducted a two-sample instrumental variable analysis using season as an instrument for maternal first-trimester 25(OH)D3 plasma levels obtained from a non-overlapping subset (n = 827) in the DNBC. RESULTS: For the combined estimate, girls and boys of mothers who had their first trimester during November-April had earlier pubertal timing than girls and boys of mothers whose first trimester occurred during May-October: -1.0 months (95% CI: -1.7 to -0.3) and -0.7 months (95% CI: -1.4 to -0.1), respectively. In the instrumental variable analysis, girls and boys also had earlier pubertal timing: respectively, -1.3 months (95% CI: -2.1 to -0.4) and -1.0 months (95% CI: -1.8 to -0.2) per SD (22 nmol/L) decrease in 25(OH)D3. CONCLUSIONS: Both first pregnancy trimester during November-April and lower 25(OH)D3 were associated with earlier pubertal timing in girls and boys.

Maternal Cigarette Smoking During Pregnancy and Genital Anomalies in Boys: A Register-Based Cohort and Sibling-Matched Design Study.

Purpose: Cryptorchidism and hypospadias share several prenatal risk factors. However, in published studies, boys exposed to cigarette smoking during pregnancy have a higher risk of cryptorchidism and a lower risk of hypospadias. Using Danish register-based data, we revisited these findings with a cohort and sibling-matched design to investigate the potential effect of shared time-stable factors. Patients and Methods: For the cohort study, we included 823,670 live-born, singleton boys born from 1991 to 2016. Crude and adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated using Cox regression models for each genital anomaly according to maternal cigarette smoking during pregnancy. For the sibling-matched design, we included 399,258 brothers and used a stratified Cox regression model creating family-adjusted results. Results: In the cohort study, we found a higher risk of cryptorchidism (aHR = 1.18, 95% CI: 1.12, 1.24) and a lower risk of hypospadias (aHR = 0.84, 95% CI: 0.76, 0.93) when comparing boys exposed to cigarette smoking with non-exposed, and for increasing numbers of cigarettes smoked. In comparison, the sibling-matched analyses suggested a slightly weaker association for cryptorchidism and an association of similar magnitude for hypospadias, both in the same direction as in the cohort study. Conclusion: Shared, familial confounding does not seem to explain earlier findings of higher risk of cryptorchidism and lower risk of hypospadias.

Prenatal nitrate exposure from diet and drinking water and timing of puberty in sons and daughters: A nationwide cohort study.

BACKGROUND: In Western countries, age at pubertal development has declined during the last century in girls, and probably also in boys. No studies have investigated whether nitrate, a widespread environmental exposure with teratogenic and hormone disrupting properties, might affect timing of puberty. OBJECTIVES: We investigated if prenatal exposure to nitrate from drinking water and diet was associated with timing of puberty. METHODS: This cohort study included 15,819 children born from 2000 to 2003 within the Danish National Birth Cohort. Self-reported information on current status of various pubertal milestones was provided every six months by a questionnaire from 11 years of age until 18 years or full maturity, whichever came first. Maternal nitrate intake from diet (mg/day) was derived from a mid-pregnancy food frequency questionnaire and individual level nitrate exposure from drinking water (mg/L) was derived using measurements from Danish public waterworks. Adjusted average differences in months in age at attaining several pubertal milestones as well as the average age difference in age at attaining all the milestones were estimated separately for diet and water using a regression model for interval-censored data. C- and E-vitamin, red meat and processed meat intake were explored as potential effect modifiers in sub-analyses. RESULTS: No strong associations were observed between prenatal exposure to nitrate and timing of puberty in children. However, sons born of mothers with a nitrate concentration in drinking water at their residential address of > 25 mg/L (half of the World Health Organisation (WHO) guideline value) compared with ≤ 1 mg/L showed a tendency towards earlier age at pubertal development with an average age difference of -1.2 months (95 % confidence interval,-3.0;0.6) for all the pubertal milestones combined. DISCUSSION: Studies including more highly exposed children are needed before the current WHO drinking water guideline value for nitrate can be considered safe concerning pubertal development.

In Utero Exposure to Glucocorticoids and Pubertal Timing in Sons and Daughters.

Early pubertal timing has been associated with adult diseases, and identifying preventable causes is of importance. In utero exposure to exogenous glucocorticoids, has been associated with changes in the reproductive hormonal axes in the children, which may influence pubertal timing. Exogenous glucocorticoids can be indicated for diseases such as asthma, allergy, skin diseases, as well as muscle and joint diseases. The aim was to explore the association between in utero exposure to glucocorticoids and pubertal timing in the children. This population-based study was conducted in the Puberty Cohort including 15,819 children, which is a sub-cohort of the Danish National Birth Cohort. Information on maternal glucocorticoid treatment was collected through interviews during pregnancy. Information on pubertal timing was obtained by questionnaires every 6 months throughout puberty, including Tanner Stages, axillary hair, acne, voice break, first ejaculation and menarche. The potential impact of confounding by indication was explored by stratifying on indication and treatment status. Overall, 6.8% of the children were exposed to glucocorticoids in utero. Exposure to glucocorticoids in utero was not associated with earlier puberty for neither boys nor girls with combined estimates of 0.4 months (95% CI: -1.5; 2.2) and -0.7 months (95% CI: -2.5; 1.2).