Birthweight and the risk of early childhood cancer among Chinese in Singapore

Birth Weight and Subsequent Risk of Total Leukemia and Acute Leukemia: A Systematic Review and Meta-Analysis

Objective: Birth weight, an important indicator of fetal nutrition and degree of development, may affect the risk of subsequent leukemia. At present, little is known about the effect of birth weight on acute myeloid leukemia (AML) and whether there is a dose-dependent relationship of birth weight with acute lymphoid leukemia (ALL) and AML. To address these questions, the present work aimed to systematically investigate the relationship between birth weight and the risk of subsequent leukemia based on the current epidemiological studies Methods: Relevant studies were systematically retrieved from electronic databases PubMed, Embase, and Cochrane Library, from inception to May 15th, 2021. Finally, 28 studies (including 21 case-control studies and 7 cohort studies) were included for the final meta-analysis. Results in cohort studies were performed by risk ratios (RRs), while those in case-control studies by odds ratios (ORs), and all results were assessed by adopting the random-effect model. Besides, a dose-dependent analysis was conducted based on the cohort studies. Results: Compared with the population with normal birth weight (NBW), the population with high birth weight (HBW) might have an increased risk of leukemia (OR 1.33, 95%CI 1.20-1.49; I ² 0%). Meanwhile, low birth weight (LBW) was associated with a decreased risk of ALL, as evidenced from the pooled analysis of case-control studies (OR 0.83, 95% CI 0.75-0.92; I ² 23.3%). However, relative to NBW population, the HBW population might have an increased risk of ALL (OR 1.28, 95% CI 1.20-1.35; I ² 7%). There was no obvious evidence supporting the relationship between LBW and the risk of AML from the pooled analysis of case-control studies (OR, 1.11 95% CI 0.87-1.42; I ² 31.7%). Conclusions: Overall, in children and young adults, HBW population may be associated with the risks of subsequent leukemia and AML relative to NBW population, but the supporting dose-dependent evidence is lacking. In addition, compared with NBW population, there is stronger evidence supporting a significantly increased risk of subsequent ALL in HBW population, and a decreased risk in LBW population in a dose-dependent manner. More prospective studies with large samples are warranted in the future to validate and complement these findings.

Maternal and perinatal characteristics, congenital malformations and the risk of wilms tumor: the ESTELLE study

PURPOSE

Wilms tumor (WT), or nephroblastoma, is an embryonic tumor that constitutes the most common renal tumor in children. Little is known about the etiology of WT. The aim of this study was to investigate whether maternal or perinatal characteristics were associated with the risk of WT.

METHODS

The ESTELLE study is a national-based case-control study that included 117 cases of WT and 1,100 controls younger than 11 years old. The cases were children diagnosed in France in 2010-2011 and the controls were frequency matched with cases by age and gender. The mothers of case and control children responded to a telephone questionnaire addressing sociodemographic and perinatal characteristics, childhood environment, and lifestyle. Unconditional logistic regression models adjusted on potential cofounders were used to estimate the odds ratios (OR) and their confidence intervals (95% CI).

RESULTS

High birth weight and the presence of congenital malformation were associated with WT (OR 1.9 [95% CI 1.0-3.7] and OR 2.5 [95% CI 1.1-5.8], respectively). No association with breastfeeding or folic acid supplementation was observed.

CONCLUSIONS

Although potential recall bias cannot be excluded, our findings reinforce the hypothesis that high birth weight and the presence of congenital malformation may be associated with an increased risk of WT. Further investigations are needed to further elucidate the possible role of maternal characteristics in the etiology of WT.

Gestational risk factors and childhood cancers: A cohort study in Taiwan

Gestational risk factors such as birth weight, gestational age and parity have been repeatedly found to be related to pediatric cancers, but few reports have emerged from Asian countries. Here we report on demographic and gestational factors in a Taiwanese cohort. Our study included all children born in Taiwan 2004-2014 for whom there was a birth record (n = 2,079,037), of which 1900 children had been diagnosed with cancer prior to age 12. We conducted multivariable hazard regression to examine associations between demographic and gestational factors with cancer. Greater parity (family with 2+ older children) was related to acute myeloid leukemia [Hazard ratio (HR) = 2.15, 95% confidence interval (CI): 1.31, 3.55), central nervous system tumors (HR = 1.67, CI: 1.13, 2.48) and neuroblastoma (HR = 1.67, CI: 1.07, 2.63). Hepatoblastoma cases had a higher risk of low birth weight (<2,500 g; HR = 3.01, CI: 1.85, 4.91), very preterm birth (<33 weeks gestation; HR = 13.71, CI: 7.45, 25.23), plural pregnancies (HR = 2.37, CI: 1.10, 5.14) and both small (HR = 2.13, CI: 1.23, 3.67) and large (HR = 1.83, CI: 1.01, 3.32) for gestational age. Germ cell tumors were more common among children born in rural areas (HR = 1.63, CI: 1.02, 2.60). Despite that Taiwan has lower rates of both high and low birthweight compared to other developed nations, we observed several similar associations to those reported in Western Countries. Further research should examine unique exposures in Taiwan that may be contributing to higher incidence of certain cancer types.

Birth Weight and Risk of Childhood Acute Lymphoblastic Leukemia in Arizona, Illinois, and Kentucky

OBJECTIVE

To confirm the previously reported increased risk of leukemia among macrosomic children (those with birth weight >4 kg).

METHODS

Birth certificates of Arizona, Illinois, and Kentucky children diagnosed as having acute lymphoblastic leukemia (ALL) before age 5 years were matched with birth certificates from leukemia-free children of the same sex, race, and ethnicity who were born in the same county on or about the same day. Odds ratios (ORs) for ALL among children of low (<2.5 kg) or high (>4 kg) birth weight were calculated by conditional logistic regression.

RESULTS

Children with high birth weight had an elevated risk of ALL in the first 5 years of life (OR 1.28, 95% confidence interval [CI] 1.01-1.61). The excess risk was confined to non-Hispanic whites (OR 1.77, 95% CI 1.27-2.48), both boys (OR 1.57, 95% CI 1.01-2.45) and girls (OR 2.10, 95% CI 1.26-3.52).

CONCLUSIONS

This study confirms the association between high birth weight and ALL previously reported by other studies in children of European ancestry. The literature on maternal risk factors for both macrosomia and ALL is reviewed, with maternal overnutrition emerging as a plausible risk factor for both outcomes.

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.

Risk of malignant childhood germ cell tumors in relation to demographic, gestational, and perinatal characteristics

BACKGROUND

Childhood germ cell tumors (GCTs) are a rare assortment of neoplasms, with mostly unknown etiology, that are believed to originate very early in life. Few studies have examined risk factors by histologic subtype, despite evidence of different risk profiles.

MATERIALS AND METHODS

In this population-based case-control study, 451 childhood malignant GCT cases ages 0-5 years were identified from the California Cancer Registry. Differentiating between common histologic subtypes, we identified 181 yolk sac tumors, 216 teratomas, and 54 rarer subtypes. Cases were linked to their birth certificates and 271,381 controls, frequency matched by birth year, were randomly selected from California birthrolls to investigate the contributions of demographic, gestational, and pregnancy factors using unconditional logistic regression analysis.

RESULTS

Compared to non-Hispanic whites, Asian/Pacific Islander children were at an increased risk for developing GCTs (odds ratio [OR]=1.94; 95% confidence interval [CI]=1.47, 2.56). Among pregnancy complications and procedures, yolk sac tumors were positively associated with the presence of fetopelvic disproportion (OR=2.97; 95% CI=1.55, 5.68), while teratomas were strongly associated with polyhydramnios or oligohydramnios (OR=14.76; 95% CI=7.21, 30.19) and the presence of an ear, face, or neck anomaly at birth (OR=93.70; 95% CI=42.14, 208.82).

CONCLUSIONS

Malignant yolk sac tumors and malignant teratomas exhibited distinct demographic and gestational characteristics; additionally, complications in pregnancy and labor may be brought on by specific histologic subtypes.

Birthweight and Childhood Cancer: Preliminary Findings from the International Childhood Cancer Cohort Consortium (I4C)

BACKGROUND

Evidence relating childhood cancer to high birthweight is derived primarily from registry and case-control studies. We aimed to investigate this association, exploring the potential modifying roles of age at diagnosis and maternal anthropometrics, using prospectively collected data from the International Childhood Cancer Cohort Consortium.

METHODS

We pooled data on infant and parental characteristics and cancer incidence from six geographically and temporally diverse member cohorts [the Avon Longitudinal Study of Parents and Children (UK), the Collaborative Perinatal Project (USA), the Danish National Birth Cohort (Denmark), the Jerusalem Perinatal Study (Israel), the Norwegian Mother and Child Cohort Study (Norway), and the Tasmanian Infant Health Survey (Australia)]. Birthweight metrics included a continuous measure, deciles, and categories (≥ 4.0 vs. < 4.0 kilogram). Childhood cancer (377 cases diagnosed prior to age 15 years) risk was analysed by type (all sites, leukaemia, acute lymphoblastic leukaemia, and non-leukaemia) and age at diagnosis. We estimated hazard ratios (HR) and 95% confidence intervals (CI) from Cox proportional hazards models stratified by cohort.

RESULTS

A linear relationship was noted for each kilogram increment in birthweight adjusted for gender and gestational age for all cancers [HR = 1.26; 95% CI 1.02, 1.54]. Similar trends were observed for leukaemia. There were no significant interactions with maternal pre-pregnancy overweight or pregnancy weight gain. Birthweight ≥ 4.0 kg was associated with non-leukaemia cancer among children diagnosed at age ≥ 3 years [HR = 1.62; 95% CI 1.06, 2.46], but not at younger ages [HR = 0.7; 95% CI 0.45, 1.24, P for difference = 0.02].

CONCLUSION

Childhood cancer incidence rises with increasing birthweight. In older children, cancers other than leukaemia are particularly related to high birthweight. Maternal adiposity, currently widespread, was not demonstrated to substantially modify these associations. Common factors underlying foetal growth and carcinogenesis need to be further explored.

Case-control study of birth characteristics and the risk of hepatoblastoma

BACKGROUND

Hepatoblastoma is a malignant embryonal tumor typically diagnosed in children younger than five years of age. Little is known on hepatoblastoma etiology.

METHODS

We matched California Cancer Registry records of hepatoblastomas diagnosed in children younger than age 6 from 1988 to 2007 to birth records using a probabilistic record linkage program, yielding 261 cases. Controls (n=218,277), frequency matched by birth year to all cancer cases in California for the same time period, were randomly selected from California birth records. We examined demographic and socioeconomic information, birth characteristics, pregnancy history, complications in pregnancy, labor and delivery, and abnormal conditions and clinical procedures relating to the newborn, with study data taken from birth certificates.

RESULTS

We observed increased risks for hepatoblastoma among children with low [1500-2499 g, Odds Ratio (OR)=2.02, 95% confidence interval (CI) 1.29-3.15] and very low birthweight (<1500 g, OR=15.4, 95% CI 10.7-22.3), preterm birth <33 weeks (OR=7.27, 95% CI 5.00, 10.6), small size for gestational age (OR=1.75, 95% CI 1.25-2.45), and with multiple birth pregnancies (OR=2.52, 95% CI 1.54-4.14). We observed a number of pregnancy and labor complications to be related to hepatoblastoma, including preeclampsia, premature labor, fetal distress, and congenital anomalies.

CONCLUSION

These findings confirm previously reported associations with low birthweight and preeclampsia. The relation with multiple birth pregnancies has been previously reported and may indicate a relation to infertility treatments.

Involvement of the IGF system in fetal growth and childhood cancer: an overview of potential mechanisms

Fetal growth is determined by a complex interplay of genetic, nutritional, environmental, and hormonal factors. Greater than expected fetal growth has been positively associated with the risk of the development of some cancers in childhood, particularly acute lymphoblastic leukemia, and the biological mechanisms underlying such associations are thought to involve insulin-like growth factors (IGFs). Circulating IGF levels are highly correlated with fetal growth, and IGFs are believed to play an important role in carcinogenesis; however, these two bodies of evidence have not been well integrated and, as a result, the potential underlying biological mechanisms linking the IGF system with the development of specific childhood cancers have not been elucidated. This review aims to draw together and summarize the literature linking the IGF system, rapidity of fetal growth, and risk of some specific childhood cancers; suggest explanations for some of the inconsistencies observed in previous studies of these associations; and propose an integrated framework for the putative involvement of the IGF system in the development of at least some childhood cancers. If the challenges involved in studying the complex IGF system can be overcome, this field presents an exciting opportunity to elucidate etiological pathways to childhood malignancies.

Birth characteristics and Wilms tumors in children in the Nordic countries: a register-based case-control study

Little is known about causes of Wilms tumor. Because of the young age at diagnosis, several studies have looked at various birth characteristics. We conducted a registry-based case-control study involving 690 cases of Wilms tumor aged 0-14 years, occurring in Denmark, Finland, Norway or Sweden during 1985-2006, individually matched to five controls drawn randomly from the Nordic childhood population. Information on birth characteristics was obtained from the population-based medical birth registries. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) using conditional logistic regression analysis. We observed a distinct association between Wilms tumor and high birth weight (≥4 kg) for girls (OR 1.97, CI 1.50-2.59) but not for boys (1.04, 0.78-1.38); overall, the OR was 1.43 (1.17-1.74). Among girls, risk increased by 28% (15-42%) per 500 g increase in birth weight. Large-for-gestational age girls also had a higher risk (2.48, 1.51-4.05), whereas no effect was seen for boys (1.12, 0.60-2.07). An association was seen with Apgar score at 5 min < 7 for both sexes combined (5.13, 2.55-10.3). ORs close to unity were seen for parental age and birth order. In our large-scale, registry-based study, we confirmed earlier observations of an association between high birth weight and risk of Wilms tumor, but we found an effect only in girls. The higher risk of infants with low Apgar score might reflect hypoxia causing cell damage, adverse side effects of neonatal treatment or reverse causation as low Apgar score might indicate the presence of a tumor.

Is birth weight associated with childhood lymphoma? A meta-analysis

Several risk factors have been identified for childhood lymphomas. The purpose of this meta-analysis was to synthesize current evidence regarding the association between birth weight with primarily the risk for non-Hodgkin lymphoma (NHL), given its similarity to acute lymphoblastic leukemia, Hodgkin lymphoma (HL) and any category of lymphoma. Two cohort (278,751 children) and seven case-control studies (2,660 cases and 69,274 controls) were included. Effects estimates regarding NHL, HL and any lymphoma were appropriately pooled using fixed or random effects model in two separate analyses: specifically, high was compared to normal or any birth weight. Similarly, low was compared to normal or any birth weight. No statistically significant association was found between high birth weight, as compared to normal birth weight, and risk for NHL plus Burkitt lymphoma (OR = 1.17, 95% CI = 0.76-1.80, random effects), HL (OR = 0.94, 95% CI = 0.64-1.38, fixed effects) or any plus Burkitt lymphoma (OR = 1.09, 95% CI = 0.76-1.56, fixed effects). A null association emerged when low was compared with normal birth weight for NHL plus Burkitt lymphoma (OR = 1.07, 95% CI = 0.71-1.62, random effects), HL (OR = 0.94, 95% CI = 0.54-1.65, fixed effects) or any plus Burkitt lymphoma (OR = 1.02, 95% CI = 0.79-1.33, fixed effects). Accordingly, no association was found when high or low birth weight was compared to any birth weight. Although current evidence suggests no association, birth weight might be a too crude indicator to reveal a genuine association of fetal growth with specific lymphoma categories; hence, there is an emerging need for use of more elaborate proxies, at least those accounting for gestational week.

Wilms' tumour: a systematic review of risk factors and meta-analysis

Wilms' tumour comprises 95% of all renal cancers among children less than 15 years of age. The purpose of this review is to examine the existing literature on perinatal and environmental risk factors for Wilms' tumour. A search for epidemiological studies that examined risk factors for Wilms' tumour was undertaken in Medline, LILACS, ISI Web of Science and Dissertation Abstracts. A total of 37 studies, including 14 cohort, 21 case-control and 2 case-cohort studies, were identified that examined environmental and perinatal risk factors. Most studies were from Western Europe and North America, and among case-control studies, 16 used randomly selected population-based controls. We observed a significantly increased risk of Wilms' tumour with maternal exposure to pesticides prior to the child's birth (OR = 1.37 [95% CI 1.09, 1.73]), high birthweight (OR = 1.36 [95% CI 1.12, 1.64]) and preterm birth (OR = 1.44 [95% CI 1.14, 1.81]), although the results regarding pesticide exposure may be subject to publication bias (Egger's test, P = 0.09). Further analyses to adjust for the heterogeneity in the results for high birthweight and preterm birth did not statistically change the significance of the results. Additionally, an increased though not statistically significant risk of Wilms' tumour was associated with maternal hypertension (OR = 1.30 [95% CI 0.99, 1.72]), and, compared with the first born, being a second or later birth was associated with a significantly decreased risk (OR = 0.82 [95% CI 0.71, 0.95]). This review suggests a role for several perinatal and environmental risk factors in the aetiology of Wilms' tumour.

Fetal growth and risk of childhood acute lymphoblastic leukemia: results from an Australian case-control study

The relation between intrauterine growth and risk of childhood acute lymphoblastic leukemia was investigated in an Australian population-based case-control study that included 347 cases and 762 controls aged <15 years recruited from 2003 to 2006. Information on proportion of optimal birth weight, a measure of the appropriateness of fetal growth, was collected from mothers by questionnaire. Data were analyzed by using logistic regression. Risk of acute lymphoblastic leukemia was positively associated with proportion of optimal birth weight; the odds ratio for a 1-standard-deviation increase in proportion of optimal birth weight was 1.18 (95% confidence interval: 1.04, 1.35) after adjustment for the matching variables and potential confounders. This association was also present among children who did not have a high birth weight, suggesting that accelerated growth, rather than high birth weight per se, is associated with risk of acute lymphoblastic leukemia. Similar associations between proportion of optimal birth weight and acute lymphoblastic leukemia were observed for both sexes and across age groups and leukemia subtypes. Results of this study confirm earlier findings of a positive association between rapidity of fetal growth and subsequent risk of acute lymphoblastic leukemia in childhood, and they are consistent with a role for insulin-like growth factors in the causal pathway.

The epidemiology of neuroblastoma: a review

Neuroblastoma is the most common tumour in children less than 1 year of age. The goal of this review was to summarise the existing epidemiological research on risk factors for neuroblastoma. A comprehensive search of the literature was undertaken using PubMed for epidemiological studies on neuroblastoma risk factors. We ascertained 47 articles which examined the risk factors. Ten studies employed population-based case-control designs; six were hospital-based case-control studies; two were cohort studies; and five employed ecological designs. Studies ranged in size from 42 to 538 cases. Three studies showed evidence of an increased risk of disease with use of alcohol during pregnancy (OR range 1.1, 12.0). Protective effects were seen with maternal vitamin intake during pregnancy (OR range 0.5, 0.7) in two studies, while risk of disease increased with maternal intake of diuretics (OR range 1.2, 5.8) in three studies. Three studies reported a decrease in risk for children with a history of allergic disease prior to neuroblastoma diagnosis (OR range 0.2, 0.4). The rarity of neuroblastoma makes this disease particularly challenging to study epidemiologically. We review the methodological limitations of prior research and make suggestions for further areas of study.

Perinatal risk factors for neuroblastoma

Neuroblastoma is the most common cancer among infants, suggesting an etiologic role for prenatal factors. In this case-cohort study, neuroblastoma cases (n = 529) diagnosed between 1985 and 2001 were identified from the New York State Cancer Registry and were matched to the electronic birth records for 1983-2001 from New York State and New York City. Controls (n = 12,010) were selected from the same birth cohorts. Analysis was stratified by age at diagnosis, with one to six months (younger infants), seven to 18 months (older infants), and older than 18 months (older children) analyzed separately. Perinatal exposure data was obtained from the birth certificates. No risk factors were identified to be consistently associated with risk across all three age groups. Generally, more risk factors were identified as associated with neuroblastoma among younger infants relative to older ages, including high birth weight, heavier maternal gestational weight gain, maternal hypertension, older maternal age, ultrasound, and respiratory distress. Among older infants, low birth weight was associated with increased risk while heavier maternal gestational weight gain was protective. In the oldest age group, first born status, primary cesarean delivery, prolonged labor and premature rupture of the membranes were associated with increased risk.

Fetal growth and the risk of childhood CNS tumors and lymphomas in Western Australia

The etiology of childhood cancers is largely unknown, although the early age at diagnosis has led to particular interest in in utero and perinatal factors. Birth weight is the most frequently studied perinatal factor in relation to risk of childhood cancers, and results have been inconsistent. We investigated whether the risk of CNS tumors and lymphomas in children was associated with three measures of the appropriateness of intra-uterine growth: proportion of optimal birth weight (POBW), birth length (POBL) and weight for length (POWFL). A cohort of 576,633 infants born in Western Australia in 1980-2004 were followed from birth to diagnosis of a CNS tumor (n = 183) or lymphoma (n = 84) before age 15, death, or December 31, 2005, and analyzed with Cox regression. Overall, there was little evidence of any association between fetal growth and risk of CNS tumors, although risk of ependymoma/choroid plexus tumors was positively associated with POBL and negatively associated with POWFL. The risk of Hodgkin and Burkitt lymphoma increased with increasing fetal growth among boys only, whereas the increased risk observed with non-Hodgkin lymphoma was only in girls. These associations between fetal growth and disease risk were also observed among children not classified as high birth weight, suggesting that accelerated growth is more important than birth weight per se. Results were similar when cases were compared with their unaffected siblings, suggesting that the increased growth associated with cancer risk was not general to the family. The associations we observed are consistent with causal pathways involving fetal growth factors.

Environmental genotoxicants/carcinogens and childhood cancer: Bridgeable gaps in scientific knowledge

Cancer in children is a major concern in many countries. An important question is whether these childhood cancers are caused by something, or are just tragic random events. Causation of at least some children's cancers is suggested by direct and indirect evidence, including epidemiological data, and animal studies that predict early life sensitivity of humans to carcinogenic effects. Candidate risk factors include genotoxic agents (chemicals and radiation), but also diet/nutrition, and infectious agents/immune responses. With regard to likelihood of risks posed by genotoxicants, there are pros and cons. The biological properties of fetuses and infants are consistent with sensitivity to preneoplastic genotoxic damage. Recent studies of genetic polymorphisms in carcinogen-metabolizing enzymes confirm a role for chemicals. On the other hand, in numerous epidemiological studies, associations between childhood cancers and exposure to genotoxicants, including tobacco smoke, have been weak and hard to reproduce. Possibly, sensitive genetic or ontogenetic subpopulations, and/or co-exposure situations need to be discovered to allow identification of susceptible individuals and their risk factors. Among the critical knowledge gaps needing to be bridged to aid in this effort include detailed tissue and cellular ontogeny of carcinogen metabolism and DNA repair enzymes, and associations of polymorphisms in DNA repair enzymes with childhood cancers. Perinatal bioassays in animals of specific environmental candidates, for example, benzene, could help guide epidemiology. Genetically engineered animal models could be useful for identification of chemical effects on specific genes. Investigations of interactions between factors may be key to understanding risk. Finally, fathers and newborn infants should receive more attention as especially sensitive targets.

Birth weight, maternal weight and childhood leukaemia

There is mounting evidence that childhood leukaemia is associated with high birth weight, but few studies have examined the relationship between leukaemia and other perinatal factors that influence birth weight, such as maternal weight or gestational weight gain. This case-cohort study included 916 acute lymphocytic leukaemia (ALL) and 154 acute myeloid leukaemia (AML) cases diagnosed prior to age 10 years between 1985 and 2001 and born in New York State excluding New York City between 1978 and 2001. Controls (n=9686) were selected from the birth cohorts for the same years. Moderate increased risk of both ALL and AML was associated with birth weight 3500 g or more. For ALL, however, there was evidence of effect modification with birth weight and maternal prepregnancy weight. High birth weight was associated with ALL only when the mother was not overweight while heavier maternal weight was associated with ALL only when the infant was not high birth weight. Increased pregnancy-related weight gain was associated with ALL. For AML, birth weight under 3000 g and higher prepregnancy weight were both associated with increased risk. These findings suggest childhood leukaemia may be related to factors influencing abnormal fetal growth patterns.

Childhood cancer following neonatal oxygen supplementation

OBJECTIVE

To evaluate the relationship between neonatal oxygen supplementation (O2) and childhood cancer in the Collaborative Perinatal Project (CPP).

STUDY DESIGN

The CPP consisted of 54,795 children born between 1959 and 1966 and followed to age 8 years. We used Cox proportional hazards modeling to examine the association between history of neonatal O2 and cancer (n = 48).

RESULTS

The hazard ratio (HR) for any O2 was 1.77 (95% confidence interval [CI] = 0.94 to 3.35). The HR for continuous duration of O2 was near 1 and not significant. However, the HRs were 0.69 (95% CI = 0.17 to 2.88) and 2.87 (95% CI = 1.46 to 5.66) when comparing 0 to 2 and 3 or more minutes of O2, respectively, to no O2. The latter association was weaker (HR = 2.00; 95% CI = 0.88 to 4.54) and not significant ( P = .10) when analysis was restricted to cancers diagnosed after age 1 year (n = 41).

CONCLUSIONS

These findings are consistent with an association between O 2 for 3 minutes or longer and cancer in childhood, and should serve as a basis for further study.