Birth weight and the risk of testicular cancer: A meta-analysis

Effects of size at birth on health, growth and developmental outcomes in children up to age 18: an umbrella review

BACKGROUND

Size at birth, an indicator of intrauterine growth, has been studied extensively in relation to subsequent health, growth and developmental outcomes. Our umbrella review synthesises evidence from systematic reviews and meta-analyses on the effects of size at birth on subsequent health, growth and development in children and adolescents up to age 18, and identifies gaps.

METHODS

We searched five databases from inception to mid-July 2021 to identify eligible systematic reviews and meta-analyses. For each meta-analysis, we extracted data on the exposures and outcomes measured and the strength of the association.

FINDINGS

We screened 16 641 articles and identified 302 systematic reviews. The literature operationalised size at birth (birth weight and/or gestation) in 12 ways. There were 1041 meta-analyses of associations between size at birth and 67 outcomes. Thirteen outcomes had no meta-analysis.Small size at birth was examined for 50 outcomes and was associated with over half of these (32 of 50); continuous/post-term/large size at birth was examined for 35 outcomes and was consistently associated with 11 of the 35 outcomes. Seventy-three meta-analyses (in 11 reviews) compared risks by size for gestational age (GA), stratified by preterm and term. Prematurity mechanisms were the key aetiologies linked to mortality and cognitive development, while intrauterine growth restriction (IUGR), manifesting as small for GA, was primarily linked to underweight and stunting.

INTERPRETATION

Future reviews should use methodologically sound comparators to further understand aetiological mechanisms linking IUGR and prematurity to subsequent outcomes. Future research should focus on understudied exposures (large size at birth and size at birth stratified by gestation), gaps in outcomes (specifically those without reviews or meta-analysis and stratified by age group of children) and neglected populations.

PROSPERO REGISTRATION NUMBER

CRD42021268843.

Small vulnerable newborns-big potential for impact

Despite major achievements in child survival, the burden of neonatal mortality has remained high and even increased in some countries since 1990. Currently, most neonatal deaths are attributable to being born preterm, small for gestational age (SGA), or with low birthweight (LBW). Besides neonatal mortality, these conditions are associated with stillbirth and multiple morbidities, with short-term and long-term adverse consequences for the newborn, their families, and society, resulting in a major loss of human capital. Prevention of preterm birth, SGA, and LBW is thus critical for global child health and broader societal development. Progress has, however, been slow, largely because of the global community's failure to agree on the definition and magnitude of newborn vulnerability and best ways to address it, to frame the problem attractively, and to build a broad coalition of actors and a suitable governance structure to implement a change. We propose a new definition and a conceptual framework, bringing preterm birth, SGA, and LBW together under a broader umbrella term of the small vulnerable newborn (SVN). Adoption of the framework and the unified definition can facilitate improved problem definition and improved programming for SVN prevention. Interventions aiming at SVN prevention would result in a healthier start for live-born infants, while also reducing the number of stillbirths, improving maternal health, and contributing to a positive economic and social development in the society.

Association of birth weight with cancer risk: a dose-response meta-analysis and Mendelian randomization study

BACKGROUND

Several articles have shown that birth weight is associated with the risk of many types of cancers. However, the results are inconsistent, and whether the relationship has a causal effect remains unknown.

METHODS

We searched the PubMed and Embase libraries up to March 2021 and selected observational studies reporting the relationship between birth weight and adult-onset cancer risk. Dose-response meta-analysis and two-sample Mendelian randomization (MR) analysis were used to estimate the effect.

RESULT

In our dose-response meta-analysis, six cancers from 46 studies were found to have significant associations with birth weight. (Ovarian cancer: RR: 1.21, 95% CI 1.01-1.44; breast cancer: RR: 1.12, 95% CI 1.08-1.16; colorectal cancer: RR: 1.20, 95% CI 1.01-1.43; endometrial cancer: RR: 0.85, 95% CI 0.78-0.93; prostate cancer: RR: 1.27, 95% CI 1.01-1.61; testicular cancer: RR: 1.21, 95% CI 1.03-1.43). As birth weight increased, the slope of the dose-response curve of breast cancer increased continuously, and the curve of testicular cancer was U-shaped. In the MR study, seven cancers were included. Only invasive mucinous ovarian cancer was found to have a causal effect on birth weight (OR: 0.62; 95% CI 0.39-0.97), while other cancers did not.

CONCLUSIONS

Our findings suggest that birth weight are unlikely to have a casual effect on risk of cancers via the MR analysis, although the dose-response meta-analysis shows that there is a nonlinear relationship between birth weight and breast cancer and testicular cancer. More relevant researches are needed to further investigate their effect.

Prenatal and Perinatal Factors and Risk of Cancer in Middle and Older Adulthood among Men

BACKGROUND

Prenatal factors have been associated with risk of cancers later in life, although studies in men have largely been case-control and focused on birth size only.

METHODS

We used data from 5,845 men in the Health Professionals Follow-up Study (HPFS) to prospectively examine associations between several prenatal and perinatal factors and incident adult cancer risk. In 1994, mothers of participants reported information on characteristics and behaviors related to their pregnancy with their sons. We used multivariable Cox proportional hazards models to calculate HRs and 95% confidence intervals (CI) of associations between prenatal and perinatal risk factors and cancer risk.

RESULTS

During 20 years of follow-up, 1,228 incident cases of overall cancer were documented. Men with a birth weight of ≥4 kg had a 21% increased risk of overall cancer (HR, 1.21; 95% CI, 1.02-1.43) compared with those with a birth weight of 2.5 to 3.9 kg. Greater weight gain during pregnancy (>13.6 kg vs. 6.8-8.6 kg) was also associated with a higher risk of overall cancer (HR, 1.22; 95% CI, 1.02-1.46), and was stronger for men whose mothers had a prepregnancy BMI<21 kg/m² (HR, 1.30; 95% CI, 1.00-1.67) compared with body mass index (BMI) ≥21 kg/m² (HR, 1.14; 95% CI, 0.85-1.51). There was no association between maternal age and overall cancer risk.

CONCLUSIONS

Higher birth weight and maternal weight gain are associated with increased cancer risk in adult men.

IMPACT

Our findings support the hypothesis that the in utero environment plays a role in the etiology of cancer in middle and older adulthood.

The effect of testicular cancer and testicular self-examination on knowledge, attitude and health beliefs in university students in Turkey

Purpose

This research was planned and applied as a descriptive study in order to determine the knowledge, attitudes and behaviors about testicular cancer (TC) and testicular self-examination (TSE) of male students who receiving health education.

Design/methodology/approach

This descriptive and cross-sectional study was conducted between May and August 2019 with male students. Early diagnosis of TC is quite important in terms of prognosis of the disease. The data were collected by using the questionnaire prepared by the researchers in accordance with the literature and the Turkish version of health belief model scale (HBMS) for TSE. The data were analyzed by number, percentage, mean and standard deviation and t test.

Findings

TSE HBMS, it was observed that the mean score of susceptibility subscale was 11.23 ± 3.73, the mean score of seriousness subscale was 28.20 ± 7.66, the mean score of benefit subscale was 21.57 ± 5.90, the mean score of the barriers subscale was 22.74 ± 5.16, the mean score of self-efficacy subscale was 9.91 ± 3.13 and the mean score of the health motivation subscale was 8.92 ± 2.84.

Originality/value

There was a statistically significant relationship between having heard of TC and health motivation (p < 0.05). There was a statistically significant relationship between the knowledge of TC and self-efficacy and health motivation (p < 0.05). There was a significant relationship between self-efficacy and TSE performing status (p < 0.05). There was also a significant relationship between the desire to obtain information about TSE and seriousness, barriers, self-efficacy and health motivation (p < 0.05). It was determined that majority of university students did not have any information about TC and TSE.

Serum polychlorinated biphenyl (PCB) levels and risk of testicular germ cell tumors: A population-based case-control study in Connecticut and Massachusetts

The incidence rate of testicular germ cell tumors (TGCT) has continuously increased in Western countries over the last several decades. Some epidemiologic studies have reported that the endocrine disrupting polychlorinated biphenyls (PCBs) in serum may be associated with TGCT risk, but the evidence is inconsistent. Our goal was to investigate whether serum levels of PCBs are associated with the increase of TGCT risk. We conducted a population-based case-control study of 308 TGCT cases and 323 controls, all residents of Connecticut and Massachusetts. Serum levels of 56 PCBs congeners were measured using gas chromatography and unconditional logistic regression model was used to evaluate the risk of TGCT associated with total PCBs exposure, groups of PCBs categorized by Wolff's functional groups, and individual PCB congeners. The results showed that there was no association between total serum levels of PCBs and risk of TGCT overall (quartile 4 (Q4) vs. quartile 1 (Q1) odds ratio (OR) and 95% confidence interval (C.I.) = 1.0 (0.6-1.9), ρ trend = 0.9). However, strong positive association was observed between total serum levels of Wolff's Group 1 (potentially estrogenic) PCBs and risk of overall TGCT (Q4 vs. Q1 OR = 2.5, 95% CI = 1.3-4.7, ρ trend <0.05) as well as seminoma and non-seminoma subtypes. Wolff's Group 1 PCB congeners that showed an increased risk of TGCT included: 25, 44, 49, 52, 70, 101, 174, and 201/177. Considering the continuing increase of TGCT, these associations should be replicated in different populations with larger sample size.

Collateral Damage: Maternal Obesity During Pregnancy Continues to Rise

Importance

The pandemic of obesity during pregnancy now afflicts 1 out of every 2 pregnant women in the United States. Even though unintended pregnancy has decreased to 45% of all pregnancies, 50% of those unintended pregnancies occur in obese women.

Objective

This study aims to identify why current lifestyle interventions for obese pregnancy are not effective and what the newer complications are for obesity during pregnancy.

Evidence Acquisition

Available literatures on current treatments for maternal obesity were reviewed for effectiveness. Emerging maternal and infant complications from obesity during pregnancy were examined for significance.

Results

Limitations in successful interventions fell into 3 basic categories to include the following: (1) preconception weight loss; (2) bariatric surgery before pregnancy; and (3) prevention of excessive gestational weight gain during pregnancy. Emerging significant physiological changes from maternal obesity is composed of inflammation (placenta and human milk), metabolism (hormones, microbiome, fatty acids), and offspring outcomes (body composition, congenital malformations, chronic kidney disease, asthma, neurodevelopment, and behavior).

Conclusions and Relevance

Are current prepregnancy lifestyle and behavioral interventions feasible to prevent maternal obesity complications? Epigenetic and metabolomic research will be critical to determine what is needed to blunt the effects of maternal obesity and to discover successful treatment.

Risk of gonadal neoplasia in patients with disorders/differences of sex development

BACKGROUND

Patients with disorders/differences of sex development (DSD), especially those possessing the Y chromosome, have a higher risk of gonadal germ-cell tumours (GCTs). We aimed to examine the incidence of different types of gonadal neoplasia and associated risk factors.

METHODS

A total of 1040 DSD patients aged ≥16 years participated in a cross-sectional multicentre European study (dsd-LIFE). Data on medical history were gathered from the patients' archival medical documents. A web-based questionnaire was filled out individually by the participants. A physical examination was performed in all, while ultrasonography of gonads was carried out in 214 and semen analysis was performed for 53 patients.

RESULTS

Germ-cell neoplasia was present in 12 % of patients with DSD and in 14 % of those with XY DSD. The highest risk (36 %) was observed in 46,XY patients with gonadal dysgenesis (GD): complete GD (33 %) and partial GD (23 %), but also in mixed GD (8 %) and complete androgen insensitivity syndrome (AIS) (6%). It was not reported in partial AIS, XX male, 46,XX DSD and congenital adrenal hyperplasia, Turner and Klinefelter syndromes, or in androgen biosynthesis defects. Benign sex cord-stromal tumours (Sertoli- and Leydig-cell tumours) were noted only in patients with complete AIS (3.1 %) and Klinefelter syndrome (14.3 %). A relationship between risk factors for GCT and gonadal neoplasia appearance, other than the Y chromosome, was not found.

CONCLUSION

Adult patients with GD and the Y chromosome have the highest risk of GCT and should be kept under thorough medical control and receive special medical follow-up to prevent the development of gonadal tumours.

Current opportunities to catalyze research in nutrition and cancer prevention - an interdisciplinary perspective

Cancer Research UK and Ludwig Cancer Research convened an inaugural international Cancer Prevention and Nutrition Conference in London on December 3-4, 2018. Much of the discussion focused on the need for systematic, interdisciplinary approaches to better understand the relationships of nutrition, exercise, obesity and metabolic dysfunction with cancer development. Scientists at the meeting underscored the importance of studying the temporal natural history of exposures that may cumulatively impact cancer risk later in life.A robust dialogue identified obesity as a major risk for cancer, and the food environment, especially high energy and low nutrient processed foods, as strong and prevalent risk factors for obesity. Further engagement highlighted challenges in the post-diagnostic setting, where similar opportunities to understand the complex interplay of nutrition, physical activity, and weight will inform better health outcomes.Going forward, holistic research approaches, encompassing insights from multiple disciplines and perspectives, will catalyze progress urgently needed to prevent cancer and improve public health.

Attitudes Toward Testicular Cancer and Self-Examination Among Northern Irish Males

Testicular cancer incidence rates are increasing worldwide making it the most common malignancy in males aged 15 to 45 years. Without a known way to prevent the disease health professionals must promote awareness and early detection. A literature review identified a scarcity of information regarding awareness and knowledge of, and attitudes toward, testicular cancer and testicular self-examination among men in Northern Ireland. This study aimed to establish baseline data for Northern Ireland using a convenience sample of 150 men, aged 18 to 45 years. The sample was recruited from across the country and so represents a range of education and area deprivation levels. An online survey was used to collect data. Results showed that while 39% of respondents correctly identified the age group at highest risk for testicular cancer, only 17% of respondents had ever heard of a testicular self-examination. Analysis revealed knowledge, awareness, and attitudes differed by age groups and area deprivation quintiles. It is recommended that health promoters in Northern Ireland and elsewhere use these findings to tailor health promotion initiatives to engage men and raise testicular cancer and self-examination awareness.

Anthropometrics at birth and risk of a primary central nervous system tumour: A systematic review and meta-analysis

BACKGROUND

The aetiology of primary central nervous system (CNS) tumours remains largely unknown, but their childhood peak points to perinatal parameters as tentative risk factors. In this meta-analysis, we opted to quantitatively synthesise published evidence on the association between birth anthropometrics and risk of primary CNS tumour.

METHODS

Eligible studies were identified via systematic literature review; random-effects meta-analyses were conducted for the effect of birth weight and size-for-gestational-age on childhood and adult primary CNS tumours; subgroup, sensitivity, meta-regression and dose-response by birth weight category analyses were also performed.

RESULTS

Forty-one articles, encompassing 53,167 CNS tumour cases, were eligible. Birth weight >4000 g was associated with increased risk of childhood CNS tumour (OR: 1.14, [1.08-1.20]; 22,330 cases). The risk was higher for astrocytoma (OR: 1.22, [1.13-1.31]; 7456 cases) and embryonal tumour (OR: 1.16, [1.04-1.29]; 3574 cases) and non-significant for ependymoma (OR: 1.12, [0.94-1.34]; 1374 cases). Increased odds for a CNS tumour were also noted among large-for-gestational-age children (OR: 1.12, [1.03-1.22]; 10,339 cases), whereas insufficient data for synthesis were identified for other birth anthropometrics. The findings remained robust across subgroup and sensitivity analyses controlling for several sources of bias, whereas no significant heterogeneity or publication bias were documented. The limited available evidence on adults (4 studies) did not reveal significant associations between increasing birth weight (500-g increment) and overall risk CNS tumour (OR: 0.99, [0.98-1.00]; 1091 cases) or glioma (OR: 1.03, [0.98-1.07]; 2052 cases).

CONCLUSIONS

This meta-analysis confirms a sizeable association of high birth weight, with childhood CNS tumour risk, particularly astrocytoma and embryonal tumour, which seems to be independent of gestational age. Further research is needed to explore underlying mechanisms, especially modifiable determinants of infant macrosomia, such as gestational diabetes.

Early life risk factors for testicular cancer: a case-cohort study based on the Copenhagen School Health Records Register

PURPOSE

One established risk factors for testicular cancer is cryptorchidism. However, it remains unclear whether cryptorchidism is a risk factor in itself or whether the two conditions share common causes in early life (estrogen hypothesis), such as birth weight and birth order. The objective of this study is to utilize data from the Copenhagen School Health Records Register (CSHRR) to evaluate cryptorchidism, birth weight and birth order as risk factors for testicular cancer.

METHODS

The study population consisted of 408 cases of testicular cancer identified by a government issued identification number linkage of the entire CSHRR with the Danish Cancer Registry and a random subsample of 4819 males from the CSHRR. The study design was case-cohort and the period of follow-up between 2 April 1968 and 31 December 2003.

RESULTS

Cryptorchidism was significantly associated with testicular cancer in crude analyses [hazard ratio (HR) = 3.60, 95% CI 2.79-4.65]. Birth weight was inversely associated with testicular cancer and no clear association with birth order was observed. The positive association between cryptorchidism and testicular cancer was only slightly attenuated controlling for birth weight and birth order and stratified on birth cohort (HR = 3.46, 95% CI 2.67-4.48).

CONCLUSION

This study confirmed the robustness of the association between cryptorchidism and testicular cancer even after adjustment for birth weight and birth order. Furthermore, the study showed an inverse association between birth weight and testicular cancer.

Potential Intervention Targets in Utero and Early Life for Prevention of Hormone Related Cancers

Hormone-related cancers have long been thought to be sensitive to exposures during key periods of sexual development, as shown by the vulnerability to such cancers of women exposed to diethylstilbestrol in utero. In addition to evidence from human studies, animal studies using new techniques, such as gene knockout models, suggest that an increasing number of cancers may be hormonally related, including liver, lung, and bladder cancer. Greater understanding of sexual development has also revealed the "mini-puberty" of early infancy as a key period when some sex hormones reach levels similar to those at puberty. Factors driving sex hormones in utero and early infancy have not been systematically identified as potential targets of intervention for cancer prevention. On the basis of sex hormone pathways, we identify common potentially modifiable drivers of sex hormones, including but not limited to factors such as obesity, alcohol, and possibly nitric oxide. We review the evidence for effects of modifiable drivers of sex hormones during the prenatal period and early infancy, including measured hormones as well as proxies, such as the second-to-fourth digit length ratio. We summarize the gaps in the evidence needed to identify new potential targets of early life intervention for lifelong cancer prevention.

Birth weight in relation to health and disease in later life: an umbrella review of systematic reviews and meta-analyses

BACKGROUND

Birth weight, a marker of the intrauterine environment, has been extensively studied in epidemiological research in relation to subsequent health and disease. Although numerous meta-analyses have been published examining the association between birth weight and subsequent health-related outcomes, the epidemiological credibility of these associations has not been thoroughly assessed. The objective of this study is to map the diverse health outcomes associated with birth weight and evaluate the credibility and presence of biases in the reported associations.

METHODS

An umbrella review was performed to identify systematic reviews and meta-analyses of observational studies investigating the association between birth weight and subsequent health outcomes and traits. For each association, we estimated the summary effect size by random-effects and fixed-effects models, the 95 % confidence interval, and the 95 % prediction interval. We also assessed the between-study heterogeneity, evidence for small-study effects and excess significance bias. We further applied standardized methodological criteria to evaluate the epidemiological credibility of the statistically significant associations.

RESULTS

Thirty-nine articles including 78 associations between birth weight and diverse outcomes met the eligibility criteria. A wide range of health outcomes has been studied, ranging from anthropometry and metabolic diseases, cardiovascular diseases and cardiovascular risk factors, various cancers, respiratory diseases and allergies, musculoskeletal traits and perinatal outcomes. Forty-seven of 78 associations presented a nominally significant summary effect and 21 associations remained statistically significant at P < 1 × 10^-6. Thirty associations presented large or very large between-study heterogeneity. Evidence for small-study effects and excess significance bias was present in 13 and 16 associations, respectively. One association with low birth weight (increased risk for all-cause mortality), two dose-response associations with birth weight (higher bone mineral concentration in hip and lower risk for mortality from cardiovascular diseases per 1 kg increase in birth weight) and one association with small-for-gestational age infants with normal birth weight (increased risk for childhood stunting) presented convincing evidence. Eleven additional associations had highly suggestive evidence.

CONCLUSIONS

The range of outcomes convincingly associated with birth weight might be narrower than originally described under the "fetal origin hypothesis" of disease. There is weak evidence that birth weight constitutes an effective public health intervention marker.

Anogenital distance as a marker of androgen exposure in humans

Abnormal foetal testis development has been proposed to underlie common disorders of the male reproductive system such as cryptorchidism, hypospadias, reduced semen quality and testicular germ cell tumour, which are regarded as components of a 'testicular dysgenesis syndrome'. The increasing trends and geographical variation in their incidence have been suggested to result from in utero exposure to environmental chemicals acting as endocrine disruptors. In rodents, the anogenital distance (AGD), measured from the anus to the base of genital tubercle, is a sensitive biomarker of androgen exposure during a critical embryonic window of testis development. In humans, several epidemiological studies have shown alterations in AGD associated with prenatal exposure to several chemicals with potential endocrine disrupting activity. However, the link between AGD and androgen exposure in humans is not well-defined. This review focuses on the current evidence for such a relationship. As in rodents, a clear gender difference is detected during foetal development of the AGD in humans which is maintained thereafter. Reduced AGD in association with clinically relevant outcomes of potential environmental exposures, such as cryptorchidism or hypospadias, is in keeping with AGD as a marker of foetal testicular function. Furthermore, AGD may reflect variations in prenatal androgen exposure in healthy children as shorter AGD at birth is associated with reduced masculine play behaviour in preschool boys. Several studies provide evidence linking shorter AGD with lower fertility, semen quality and testosterone levels in selected groups of adults attending andrology clinics. Overall, the observational data in humans are consistent with experimental studies in animals and support the use of AGD as a biomarker of foetal androgen exposure. Future studies evaluating AGD in relation to reproductive hormones in both infants and adults, and to gene polymorphisms, will help to further delineate the effect of prenatal and postnatal androgen exposures on AGD.

Cannabis exposure and risk of testicular cancer: a systematic review and meta-analysis

BACKGROUND

The aetiology of testicular cancer remains elusive. In this manuscript, we review the evidence regarding the association between cannabis use and testicular cancer development.

METHODS

In this systematic review and meta-analysis, we reviewed literature published between 1(st) January 1980 and 13(th) May 2015 and found three case-control studies that investigated the association between cannabis use and development of testicular germ cell tumours (TGCTs).

RESULTS/CONCLUSIONS

Using meta-analysis techniques, we observed that a) current, b) chronic, and c) frequent cannabis use is associated with the development of TGCT, when compared to never-use of the drug. The strongest association was found for non-seminoma development--for example, those using cannabis on at least a weekly basis had two and a half times greater odds of developing a non-seminoma TGCT compared those who never used cannabis (OR: 2.59, 95% CI 1.60-4.19). We found inconclusive evidence regarding the relationship between cannabis use and the development of seminoma tumours. It must be noted that these observations were derived from three studies all conducted in the United States; and the majority of data collection occurred during the 1990's.

Cancer risks in twins and singletons from twin and non-twin families

The unique intrauterine environment has been proposed to put twins at increased risk of certain cancers compared to singletons, still large population comparisons have generally indicated lower risks in twins. To improve the understanding of potential twin influence on cancer we compared twins to their singletons siblings, to target a unique twinning influence. Singletons from twin families were contrasted to singletons from non-twin families to further capture potential twin family influence on risk of cancer. Family relations were identified using the Swedish Multi-Generation Register. Among individuals born between 1932 and 1958, 49,156 twins and N = 35,227 singletons were identified from 18,098 unique twin families. All incident cases of specific cancer types were identified in the National Cancer Register up to the end of 2007. Standardized survival functions were estimated using weighted Cox proportional hazard regression and the corresponding cumulative risks plotted against age. Overall, primary cancers were identified in 9% and 18% of all male and female twins, compared to 11% and 19% of their male and female singleton siblings. When specific cancer sites were compared using standardized cumulative risk plots, no consistent statistically significant differences were noted either between twins and singletons of twin families or between singletons of twin and non-twin families. Despite a different intrauterine experience, twinning does not seem to have any greater negative influence on life-time risks of cancer. The findings also indicate that twin family membership has no substantial influence on cancer risks.

Puberty in children born small for gestational age

Small for gestational age (SGA) children are more prone to have precocious pubarche and exaggerated precocious adrenarche, an earlier onset of pubertal development and menarche, and faster progression of puberty than children born of appropriate for gestational age (AGA) size. The majority of studies investigating the onset of puberty in children born SGA and AGA established that, although puberty begins at an appropriate time (based on chronological age and actual height) in SGA children, onset is earlier relative to AGA children. Evaluating pubertal growth in SGA children, a more modest bone age delay from chronological age at the onset of puberty and more rapid bone maturation during puberty compared to AGA children were reported. Peak height velocity in adolescence is reached at an earlier pubertal stage and lasts for a shorter period in children born SGA than in those born AGA. These differences lead to an earlier fusion of the growth plates and a shorter adult height. The pathophysiological mechanism underlying the unique pubertal growth pattern of children born SGA remains unclear. However, it seems that this is not only related to birth weight, gestational age, adiposity or obesity, but that there may also be an influence of rapid weight gain in early childhood on pubertal onset: excess weight gain in childhood may be related to central adiposity, decreased insulin sensitivity, and increased IGF-I levels and might thus predispose to precocious pubarche.

Is fetal macrosomia related to blood pressure among adolescents? A birth cohort study in China

Birth weight (BW) has effects on blood pressure (BP). In order to explore the effects of macrosomia on BP in childhood and in adolescence, a longitudinal cohort study was conducted in Wuxi, China. Subjects with BW ≥4000 g, born in 1993-1995, were the exposed group; the unexposed comparisons were matched by year of birth and sex of infant, with BW of 2500-4000 g. Follow-ups in 2005-6 and 2011-12 were conducted, and height, weight and BP were measured by trained doctors. Multi-mixed models in SAS were used to control for repeated measures to explore the effects of fetal macrosomia on BP. At the inception of the cohort, 1595 pairs of participants were recruited. At the end, 1112 in the exposed group and 1126 in the unexposed group finished both follow-ups. Among adolescents, mean (s.d.) of systolic BP (SBP) was 110.83 (9.43)  mm  Hg, which was statistically significantly higher than that in the unexposed group (mean ± s.d.: 109.33 ± 9.26)  mm  Hg (P=0.0002). After adjusting the repeated measures and birth year, sex, mother's occupation and delivery age, adding weight during pregnancy, hypertension during delivery, gestational age and parity, being a picky eater in childhood, the macrosomia group had higher SBP than the normal BW group; the parameter estimate value was 1.03 (s.e.=0.30). When BMI in childhood and BMI in adolescence were added in the multi-model, the estimated β was 0.71 (s.e.=0.29). No statistically significant effect of macrosomia was found on diastolic BP among adolescents in the multianalysis.

Maternal obesity, gestational weight gain and diet as determinants of offspring long term health

This review addresses the increasingly prolific literature from studies in man and animals suggesting that maternal obesity, a diet rich in calories or excess gestational weight gain may, through perturbation of the intrauterine environment, lead to lifelong risk of obesity and related disorders in the child. In addressing maternal- child obesity relationships it remains a challenge to distinguish the influence of the intrauterine environment from the contribution of shared genetic traits, and to adequately adjust for postnatal determinants of childhood obesity. Studies in genetically identical rodents convincingly show that maternal obesity, as well as elements of a hypercalorific diet can permanently influence offspring risk of obesity, and are these are supported by studies in larger mammals. Importantly, dissection of the mechanism in animals has led to description of novel interactive pathways between maternal environment and fetus which are amenable to investigation in humans.

Transgenerational epigenetic effects of the Apobec1 cytidine deaminase deficiency on testicular germ cell tumor susceptibility and embryonic viability

Environmental agents and genetic variants can induce heritable epigenetic changes that affect phenotypic variation and disease risk in many species. These transgenerational effects challenge conventional understanding about the modes and mechanisms of inheritance, but their molecular basis is poorly understood. The Deadend1 (Dnd1) gene enhances susceptibility to testicular germ cell tumors (TGCTs) in mice, in part by interacting epigenetically with other TGCT modifier genes in previous generations. Sequence homology to A1cf, the RNA-binding subunit of the ApoB editing complex, raises the possibility that the function of Dnd1 is related to Apobec1 activity as a cytidine deaminase. We conducted a series of experiments with a genetically engineered deficiency of Apobec1 on the TGCT-susceptible 129/Sv inbred background to determine whether dosage of Apobec1 modifies susceptibility, either alone or in combination with Dnd1, and either in a conventional or a transgenerational manner. In the paternal germ-lineage, Apobec1 deficiency significantly increased susceptibility among heterozygous but not wild-type male offspring, without subsequent transgenerational effects, showing that increased TGCT risk resulting from partial loss of Apobec1 function is inherited in a conventional manner. By contrast, partial deficiency in the maternal germ-lineage led to suppression of TGCTs in both partially and fully deficient males and significantly reduced TGCT risk in a transgenerational manner among wild-type offspring. These heritable epigenetic changes persisted for multiple generations and were fully reversed after consecutive crosses through the alternative germ-lineage. These results suggest that Apobec1 plays a central role in controlling TGCT susceptibility in both a conventional and a transgenerational manner.

The maternal womb: a novel target for cancer prevention in the era of the obesity pandemic?

The dramatic rise in worldwide prevalence of obesity has necessitated the search for more efficacious antiobesity strategies to counter the increased cancer risks in overweight and obese individuals. The mechanistic pathways linking obesity status with adult chronic diseases such as cancer remain incompletely understood. A growing body of evidence suggests that novel approaches and interventional agents to disrupt the feed-forward cycle of maternal to offspring obesity transfer that is initiated in utero will be important for stemming both the obesity pandemic and the associated increase in cancer incidence. The convergence of multiple research areas including those encompassing the insulin and insulin-like growth factor systems, epigenetics, and stem cell biology is providing insights into the potential for cancer prevention in adult offspring previously exposed to the intrauterine environment of overweight/obese mothers. Here, we review the current state of this nascent research field, with a focus on three major cancers, namely breast, colorectal, and liver, and suggest some possible future directions to optimize its impact for the health of future generations.

Male reprotoxicity and endocrine disruption

Mammalian reproductive tract development is a tightly regulated process that can be disrupted following exposure to drugs, toxicants, endocrine-disrupting chemicals (EDCs), or other compounds via alterations to gene and protein expression or epigenetic regulation. Indeed, the impacts of developmental exposure to certain toxicants may not be fully realized until puberty or adulthood when the reproductive tract becomes sexually mature and altered functionality is manifested. Exposures that occur later in life, once development is complete, can also disrupt the intricate hormonal and paracrine interactions responsible for adult functions, such as spermatogenesis. In this chapter, the biology and toxicology of the male reproductive tract is explored, proceeding through the various life stages including in utero development, puberty, adulthood, and senescence. Special attention is given to the discussion of EDCs, chemical mixtures, low-dose effects, transgenerational effects, and potential exposure-related causes of male reproductive tract cancers.

Induction and persistence of abnormal testicular germ cells following gestational exposure to di-(n-butyl) phthalate in p53-null mice

Phthalate esters are commonly used plasticizers found in many household items, personal care products, and medical devices. Animal studies have shown that in utero exposure to di-(n-butyl) phthalate (DBP) within a critical window during gestation causes male reproductive tract abnormalities resembling testicular dysgenesis syndrome. Our studies utilized p53-deficient mice for their ability to display greater resistance to apoptosis during development. This model was chosen to determine whether multinucleated germ cells (MNG) induced by gestational DBP exposure could survive postnatally and evolve into testicular germ cell cancer. Pregnant dams were exposed to DBP (500 mg/kg/day) by oral gavage from gestational day 12 until birth. Perinatal effects were assessed on gestational day 19 and postnatal days 1, 4, 7, and 10 for the number of MNGs present in control and DBP-treated p53-heterozygous and null animals. As expected, DBP exposure induced MNGs, with greater numbers found in p53-null mice. Additionally, there was a time-dependent decrease in the incidence of MNGs during the early postnatal period. Histologic examination of adult mice exposed in utero to DBP revealed persistence of abnormal germ cells only in DBP-treated p53-null mice, not in p53-heterozygous or wild-type mice. Immunohistochemical staining of perinatal MNGs and adult abnormal germ cells was negative for both octamer-binding protein 3/4 and placental alkaline phosphatase. This unique model identified a role for p53 in the perinatal apoptosis of DBP-induced MNGs and provided insight into the long-term effects of gestational DBP exposure within a p53-null environment.

Insulin receptor and cancer

The widespread epidemic of obesity and type 2 diabetes has raised concern for the impact of these disorders as risk factors for cancer and has renewed the interest for studies regarding the involvement of hyperinsulinemia and insulin receptor (IR) in cancer progression. Overexpression of IR in cancer cells may explain their increased sensitivity to hyperinsulinemia. Moreover, IR isoform A (IR-A) together with autocrine production of its ligand IGF2 is emerging as an important mechanism of normal and cancer stem cell expansion and is a feature of several malignancies. De novo activation of the IR-A/IGF2 autocrine loop also represents a mechanism of resistance to anticancer therapies. Increasing knowledge of the IR role in cancer has important implications for cancer prevention, which should include control of insulin resistance and hyperinsulinemia in the population and meticulous evaluation of new antidiabetic drugs for their metabolic:mitogenic ratio. We are now aware that several anticancer treatments may induce or worsen insulin resistance that may limit therapy efficacy. Future anticancer therapies need to target the IR-A pathway in order to inhibit the tumor promoting effect of IR without impairing the metabolic effect of insulin.

Prematurity: an overview and public health implications

The high rate of premature births in the United States remains a public health concern. These infants experience substantial morbidity and mortality in the newborn period, which translate into significant medical costs. In early childhood, survivors are characterized by a variety of health problems, including motor delay and/or cerebral palsy, lower IQs, behavior problems, and respiratory illness, especially asthma. Many experience difficulty with school work, lower health-related quality of life, and family stress. Emerging information in adolescence and young adulthood paints a more optimistic picture, with persistence of many problems but with better adaptation and more positive expectations by the young adults. Few opportunities for prevention have been identified; therefore, public health approaches to prematurity include assurance of delivery in a facility capable of managing neonatal complications, quality improvement to minimize interinstitutional variations, early developmental support for such infants, and attention to related family health issues.

Birth weight and subsequent risk of obesity: a systematic review and meta-analysis

This report describes the association between birth weight (BW) and obesity. Screening of 478 citations from five electronic databases resulted in the inclusion of 33 studies, most of medium quality. The meta-analysis included 20 of these published studies. The 13 remaining articles did not provide sufficient dichotomous data and were systematically reviewed, revealing results consistent with the meta-analysis. Our results revealed that high BW (>4000 g) was associated with increased risk of obesity (odds ratio [OR], 2.07; 95% confidence interval [CI], 1.91-2.24) compared with subjects with BW ≤ 4000 g. Low BW (<2500 g) was associated with decreased risk of obesity (OR, 0.61; 95% CI, 0.46-0.80) compared with subjects with BW ≥ 2500 g. However, when two studies exhibited selection bias were removed, the results indicated no significant association between low BW and obesity (OR, 0.77; 95% CI, 0.58-1.04). Sensitivity analyses showed that differences in the study design, sample size and quality grade of the study had an effect on the low BW/obesity association, which low BW was not associated with the risk of obesity in cohort studies, studies with large sample sizes and studies with high quality grades. Pooled results were similar when normal birth weight (2500-4000 g) was used as the reference category. Subgroup analyses based on different growth and developmental stages (pre-school children, school children and adolescents) also revealed that high BW was associated with increased risk of obesity from childhood to early adulthood. No significant evidence of publication bias was present. These results suggest that high BW is associated with increased risk of obesity and may serve as a mediator between prenatal influences and later disease risk.

Maternal body mass index and risk of testicular cancer in male offspring: a systematic review and meta-analysis

OBJECTIVES

To date a number of studies have examined the association between maternal weight and testicular cancer risk although results have been largely inconsistent. This systematic review and meta-analysis investigated the nature of this association.

METHODS

Search strategies were conducted in Ovid Medline (1950-2009), Embase (1980-2009), Web of Science (1970-2009), and CINAHL (1937-2009) using keywords for maternal weight (BMI) and testicular cancer.

RESULTS

The literature search produced 1689 hits from which 63 papers were extracted. Only 7 studies met the pre-defined criteria. Random effects meta-analyses were conducted. The combined unadjusted OR (95% CI) of testicular cancer in the highest reported category of maternal BMI compared with the moderate maternal BMI was 0.82 (0.65-1.02). The Cochran's Q P value was 0.82 and the corresponding I(2) was 0%, both indicating very little variability among studies. The combined unadjusted OR (95% CI) for testicular cancer risk in the lowest reported category of maternal BMI compared to a moderate maternal BMI category was 0.88 (0.65-1.20). The Cochran's Q P value was 0.05 and the corresponding I(2) was 54%, indicating evidence of statistical heterogeneity. The combined unadjusted OR (95% CI) of testicular cancer risk per unit increase in maternal BMI was 1.01 (0.97-1.06). The Cochran's Q test had a P value of 0.05 and the corresponding I(2) was 55% indicating evidence of statistical heterogeneity.

CONCLUSION

This meta-analysis, which included a small number of studies, showed that a higher maternal weight does not increase the risk of testicular cancer in male offspring. Though an inverse association between high maternal BMI and testicular cancer risk was detected, it was not statistically significant. Further primary studies with adjustment for appropriate confounders are required.

Developmental plasticity of stem cells and diseases

Stem cells, which reside in most tissues with high plasticity of self-renewal and differentiation, play a critical role in the development and maintenance processes of many tissues. It is reasonable to suspect that many undefined chronic diseases are caused by the malfunction of stem cells. In this hypothesis, we try to explain the origin of undefined chronic diseases by the developmental plasticity of stem cells. Chronic diseases are phenotypes of stem cells' malfunction. Mutations of multipotent stem cells at the prenatal stage can be used to explain phenomena of early development of diseases. In addition, stem cells accumulate mutations from fetus stage to aging period and usually develop chronic diseases in late life periods.

Growth hormone treatment in children is not associated with an increase in the incidence of cancer: experience from KIGS (Pfizer International Growth Database)

OBJECTIVE

To assess the incidence of cancer in patients treated with growth hormone (GH) in KIGS - the Pfizer International Growth Database-without cancer or any other condition in medical history known to increase the risk of cancer.

STUDY DESIGN

Data were analyzed from patients with growth disorders enrolled in an observational survey KIGS who had no known increased risk of developing cancer before starting recombinant human GH treatment. The incidence of cancer in this patient cohort (overall, site-specific, and according to etiology of growth disorder) was compared with the incidence in the general population by using the standardized incidence ratio (ie, relating the observed to expected number of cases with stratification for age, sex, and country).

RESULTS

A total of 32 new malignant neoplasms were reported in 58 603 patients, versus the 25.3 expected (incidence, 16.4 per 100 000 patient-years; standardized incidence ratio, 1.26; 95% confidence interval, 0.86-1.78). No category of growth disorder showed a statistically significant difference in observed compared with the expected number of cases.

CONCLUSION

There is no evidence in this series that GH treatment in young patients with growth disorders results in an increased risk of developing cancer relative to that expected in the normal population. However, surveillance for an extended time should continue to allow further assessment.

A systematic review and meta-analysis of perinatal variables in relation to the risk of testicular cancer--experiences of the son

BACKGROUND

We undertook a systematic review and meta-analysis of perinatal variables in relation to testicular cancer risk, with a specific focus upon characteristics of the son.

METHODS

Literature databases Scopus, EMBASE, PubMed and Web of Science were searched using highly sensitive search strategies. Of 5865 references retrieved, 67 articles met the inclusion criteria, each of which was included in at least one perinatal analysis.

RESULTS

Random effects meta-analysis produced the following results for association with testicular cancer risk: birth weight [per kilogram, odds ratio (OR) = 0.94, 95% confidence interval (CI) 0.88-1.01, I(2)= 12%], low birth weight (OR = 1.34, 95% CI 1.08-1.67, I(2)= 51%), high birth weight (OR = 1.05, 95% CI 0.96-1.14, I(2)= 0%), gestational age (per week, OR = 0.95, 95% CI 0.92-0.98, I(2)= 38%; low vs not, OR = 1.31, 95% CI 1.07-1.59, I(2)= 49%), cryptorchidism (OR = 4.30, 95% CI 3.62-5.11, I(2)= 44%), inguinal hernia (OR = 1.63, 95% CI 1.37-1.94, I(2)= 38%) and twinning (OR = 1.22, 95% CI 1.03-1.44, I(2)= 22%). Meta-analyses of the variables birth length, breastfeeding and neonatal jaundice did not provide evidence for an association with testicular cancer risk. When low birth weight was stratified by data ascertainment (record/registry vs self-report), only the category of self-report was indicative of an association. Meta-regression of data ascertainment (record/registry vs self-report) inferred that record-/registry-based studies were less supportive of an association with gestational age (per week = 0.97, 95% CI 0.94-1.00, I(2)( )= 29%; low vs not = 1.08, 95% CI 0.91-1.28, I(2)= 32%).

CONCLUSION

In conclusion, this systematic review and meta-analysis finds evidence that cryptorchidism, inguinal hernia and twinning, and tentative evidence that birth weight and gestational age, are associated with risk of testicular cancer.

Gender-specific differences in birthweight and the odds of puberty: NHANES III, 1988-94

The association between birthweight and the odds ratio (OR) of pubertal status in girls aged between 8 and 11 and in boys aged between 8 and 12 was examined using the 1988-94 Third National Health and Nutrition Examination Survey (NHANES III). Girls (n = 956), and boys (n = 1199), who had data on birthweight and Tanner staging were included. Maternal-reported birthweight, smoking in pregnancy and other information were provided in a home interview, while Tanner staging to assess pubertal status was part of a medical examination. Multiple logistic regression models were computed for the endpoints of the OR [95% confidence interval (CI)] of being Tanner Stage 2+ vs. 1 or being 2+ vs. 1 in an asynchronous pubertal pathway after adjustment for the complex sampling design of NHANES, age, race, height and body mass index (BMI). Birthweight was not associated with the OR of Tanner stage 2+ among girls; however, boys who were low birthweight (<2500 g) and boys born higher than average birthweight (3500-3999 g) were more likely to be Tanner stage 2+ than 1. Childhood BMI was associated with the OR of having entered puberty among girls, but not boys. In an analysis of asynchronous maturation, girls born at high birthweight (>4000 g) were more likely to have breast development 3+ than girls of normal birthweight, OR = 3.18 [95% CI 1.39, 8.25]. Thus, the birthweight-puberty association varies by gender and by pubertal pathway. Our findings need replication in prospective longitudinal studies, and research to understand the mechanisms underlying the relation of early life exposures to cancer risk.

Gonadal tumours and DSD

Disorders of sex development (DSD), previously referred to as intersex, has been recognised as one of the main risk factors for development of type II germ cell tumours (GCTs), that is, seminomas/dysgerminomas and non-seminomas (e.g., embryonal carcinoma, yolk sac tumour, choriocarcinoma and teratoma). Within the testis, this type of cancer is the most frequent malignancy in adolescent and young adult Caucasian males. Although these males are not known to have dysgenetic gonads, the similarities in the resulting tumours suggest a common aetiological mechanism(s),--genetically, environmentally or a combination of both. Within the group of DSD patients, being in fact congenital conditions, the risk of malignant transformation of germ cells is highly heterogeneous, depending on a number of parameters, some of which have only recently been identified. Understanding of these recent insights will stimulate further research, with the final aim to develop an informative clinical decision tree for DSD patients, which includes optimal (early) diagnosis without overtreatment, such as prophylactic gonadectomy in the case of a low tumour risk.

Human testicular (non)seminomatous germ cell tumours: the clinical implications of recent pathobiological insights

Human germ cell tumours (GCTs) comprise several types of neoplasias with different pathogeneses and clinical behaviours. A classification into five subtypes has been proposed. Here, the so-called type II testicular GCTs (TGCTs), ie the seminomas and non-seminomas, will be reviewed with emphasis on pathogenesis and clinical implications. Various risk factors have been identified that define subpopulations of men who are amenable to early diagnosis. TGCTs are omnipotent, able to generate all differentiation lineages, both embryonic and extra-embryonic, as well as the germ cell lineage itself. The precursor lesion, composed of primordial germ cells/gonocytes, is referred to as carcinoma in situ of the testis (CIS) and gonadoblastoma of the dysgenetic gonad. These pre-malignant cells retain embryonic characteristics, which probably explains the unique responsiveness of the derived tumours to DNA-damaging agents. Development of CIS and gonadoblastoma is crucially dependent on the micro-environment created by Sertoli cells in the testis, and granulosa cells in the dysgenetic gonad. OCT3/4 has high sensitivity and specificity for CIS/gonadoblastoma, seminoma, and embryonal carcinoma, and is useful for the detection of CIS cells in semen, thus a promising tool for non-invasive screening. Overdiagnosis of CIS due to germ cell maturation delay can be avoided using immunohistochemical detection of stem cell factor (SCF). Immunohistochemistry is helpful in making the distinction between seminoma and embryonal carcinoma, especially SOX17 and SOX2. The different non-seminomatous histological elements can be recognized using various markers, such as AFP and hCG, while others need confirmation. The value of micro-satellite instability as well as BRAF mutations in predicting treatment resistance needs validation in prospective trials. The availability of representative cell lines, both for seminoma and for embryonal carcinoma, allows mechanistic studies into the initiation and progression of this disease.

Maternal smoking during pregnancy and testicular cancer in the sons: a nested case-control study and a meta-analysis

Some large ecological studies have noted a significant association of testicular cancer (TC) with maternal smoking during pregnancy, while several more controlled studies have been negative. It has been difficult to obtain reliable data on exposure because of the long lag time to cancer diagnosis. We performed a case-control study nested within Finnish, Swedish and Icelandic maternity cohorts exploiting early pregnancy serum samples to evaluate the role of maternal smoking in the risk of TC in the offspring. After reviewing the literature, we also performed a meta-analysis of published studies. For each index mother of the TC patient, three to nine matched control mothers with a cancer-free son born at the same time as the TC case were identified within each cohort. First trimester sera were retrieved from the 70 index mothers and 519 control mothers and were tested for cotinine level by a novel HPLC-MS-MS method developed. No statistically significant association between maternal cotinine level and risk of TC in the offspring was found (OR 0.68; 95% CI 0.35, 1.34). This is the first study based on individual exposure measurements. Its results agree with our meta-analysis of seven previous epidemiological studies (total number of 2149 cases, 2762 controls) using indirect exposure assessment (OR 1.0; 95% CI 0.88, 1.12).

Impact of being born small for gestational age on onset and progression of puberty

Children born small for gestational age (SGA) are at higher risk for perinatal morbidity, mortality and chronic diseases in later life. There is increasing evidence for a link between prenatal growth and pubertal development, but studies concerning the timing, duration and progression of puberty in these children are scarce and the results are difficult to compare due to the various methodologies employed. Most boys born SGA have normal pubertal timing, but often attain an adult height below the target height. In girls, most studies document a relationship between intra-uterine growth retardation and earlier pubertal development or normal timing but with rapid progression. This chapter will discuss the factors that could influence pubertal development in children born SGA and the information reported to date.

Infant feeding and the incidence of endometrial cancer

Biological mechanisms could support both an inverse and a direct association between exposure to breast milk in infancy and the risk of cancer. Having been breast-fed has been investigated in relation to the risk of breast and other cancer sites, and conflicting results have been reported. The association between infant feeding and the risk of endometrial cancer has not been explored. From 1976 to 2004, we followed 74,757 cancer-free participants in the Nurses' Health Study who had not undergone hysterectomy. Information on infant feeding was self-reported by study participants. A total of 708 incident cases of endometrial cancer were diagnosed during follow-up. After adjusting for age, family history of endometrial cancer, birth weight, premature birth, and birth order, the incidence of endometrial cancer was not associated with ever having been breast-fed (hazards ratio, 0.94; 95% confidence interval, 0.79-1.11) or duration of having been breast-fed [hazards ratio (95% confidence interval): 1.11 (0.80-1.54), 0.84 (0.62-1.13), 1.02 (0.79-1.31), respectively, for < or =3, 4-8, and > or =9 months of having been breastfed; P for trend = 0.88]. There was no significant effect modification by menopausal status, anthropometric factors (somatotype at age 5 or 10 years, body mass index at age 18 years, or current body mass index), or by other early-life exposures (birth weight, premature birth or exposure to parental smoking in childhood). Additional adjustment for adulthood risk factors of endometrial cancer did not materially change the results. Having been breast-fed was not associated with the incidence of endometrial cancer in this cohort, but statistical power for analyses restricted to premenopausal women was limited.

Longitudinal study on birthweight and the incidence of endometrial cancer

From 1976 to 2004, we followed 71,751 participants of the Nurses' Health Study and identified 676 invasive endometrial cancer cases. Birthweight, assessed in 1992, was not associated with the incidence of endometrial cancer. No effect modification by menopausal status was observed, but statistical power to detect an interaction was limited.

Birth weight and melanoma risk: a population-based case-control study

We investigated whether lower birth weight was associated with lower risk of melanoma later in life. This population-based case–control study included all incident cases of histologically verified invasive melanoma diagnosed until 31 December 2003 in the Norwegian population born between 1967 and 1986 (n=709). The control group without malignant disease was established by random sampling from the same source population as the cases (n=108 209). Data on birth weight, gender, mother's residence and parental age at the time of birth were collected from the Medical Birth Registry of Norway and data on cancer from the Cancer Registry of Norway. The Mantel–Haenszel test of linear trend showed no trend in risk across the birth weight categories: individuals in the highest quartile of birth weight (⩾3860 g) had an odds ratio (OR) of 1.19 (95% confidence interval, CI: 0.77–1.84) compared to individuals with birth weight <2500 g. The adjusted OR was 0.81 (95% CI: 0.52–1.26) for birth weight below 2500 g (exposed). Though not statistically significant, the results suggest that low birth weight might influence the risk of melanoma later in life.

Testicular cancer in twins: a meta-analysis

In a meta-analysis of testicular cancer in twins, twins had a 30% increased risk (estimate 1.31, 95% CI 1.1–1.6), providing indirect support for the hypothesis that in utero hormone variations influence risk of testicular cancer. The summary-estimate for dizygotic twins was 1.3 (1.0–1.7) and for monozygotic or same sex twins 1.4 (1.2–1.8).