Paternal age and the risk of birth defects in Norway

PURPOSE: We studied 1,869,388 births from The Medical Birth Registry of Norway to assess the effect of father's age on risks of birth defects in offspring. METHOD: Thirteen separate categories were studied including pooled categories of neural tube defects and any type of defect. We used logistic regression models to adjust for maternal age, year of birth, maternity institution, parity, and correlation between siblings. RESULTS: There was little evidence of increased risk by high paternal age for any category of defects, except for a category of "other central nervous system" where risk estimates were 2.5-fold (95% CI: 1.2-5.5) for fathers aged between 45 and 49 years compared with the reference age group (25-29 years). The risk for neural tube defects was 1.3-fold (95% CI: 1.1-1.5) when the father was aged between 20 and 24 years relative to the reference. A pattern of moderately higher risks for younger fathers was consistent for anencephaly and spina bifida. Increased risk of heart defects was also estimated among children of young fathers. CONCLUSIONS: This study does not show consistent evidence that paternal ageing is a risk for birth defects among offspring. Low paternal age, or factors associated with younger parents, may however be associated with increased risk of neural tube defects in their offspring.     

Demographic characteristics in adult paternity for first births to adolescents under 15 years of age.

PURPOSE: To examine parental demographic characteristics by adult (> or = 20 years at baby's conception) and teenage (< 20 years at baby's conception) paternity in births to very young adolescents (< 15 years at baby's conception). METHODS: This was a population-based, retrospective cohort analysis of all 12,317 very young adolescent mothers residing in California with a first singleton live birth during 1993-1995. Risks for adult, compared to teenage, paternity were evaluated using multivariate logistic regression. RESULTS: Adult fathers, responsible for 26.7% of births to very young adolescents, were a mean of 8.8 years older than the mother. The risk factors for adult compared to adolescent paternity were as follows: father's educational attainment of at least 3 years below that considered adequate for his age [adjusted odds ratio (AOR) = 8.34], father's (AOR = 2.46) or mother's (AOR = 1.36) educational attainment 1-2 years below that considered adequate for their age, mother's birthplace outside the United States (AOR = 3.12), and father's Hispanic ethnicity (AOR = 1.60) or African-American race (AOR = 1.50). CONCLUSIONS: Adult fathers were responsible for over one quarter of the births in our study. Adolescent pregnancy prevention focusing on younger adolescents must programmatically address adult paternity. Variations in adult paternity patterns across cultural groups suggest that we need further study of the role that cultural beliefs and practices play in very young adolescent pregnancy.     

Epidemiological study on passive smoking among Japanese infants and smoking behavior of their respective parents: a nationwide cross-sectional survey

BACKGROUND: Passive smoking is a well-known health hazard for infants. This study was conducted to: (1) estimate the prevalence of passive smoking among Japanese infants and (2) clarify the prevalence of indoor smoking and associating factors among parents having infants. METHODS: Subjects were all 53,575 infants born throughout Japan on January 10-17, 2001 or July 10-17, 2001. When the infants reached 6 months of age, the questionnaires were mailed to the homes. Family members answered questions that included information about the current smoking behavior of the parents. RESULTS: A total of 44,562 questionnaires (83.2%) were analyzed. The prevalence of smoking among the mothers and the fathers were 17.1% and 63.5%. The percentages of mothers and fathers who smoked indoors were 12.1% and 36.2%. The percentage of households where mothers and/or fathers smoked indoors was 37.5%. Multivariate logistic analysis indicated that young age, having a spouse who was a smoker, infants having many siblings, the mother not breast-feeding, and lower annual incomes had significantly higher odds ratios for both the mother's and the father's indoor smoking. CONCLUSIONS: Passive smoking is common among Japanese infants. To protect Japanese infants from passive smoking, further public health measures must be taken.     

Risk factors for asthma and cough among Hispanic children in the southwestern United States of America, 2003-2004.

OBJECTIVES: To investigate the impact of environmental tobacco smoke (ETS) exposure and mother's place of birth (Mexico vs. United States of America) on the prevalence of asthma and dry nighttime cough among children 2-12 years old residing in the southwestern United States. METHODS: Data were collected from November 2003 through March 2004 as part of a health survey of Hispanic mothers with young children who sought emergency, nutrition, or other clinical services. Information about respiratory health was obtained for one randomly selected child per United States-born (no. = 144) or Mexico-born (no. = 125) mother. Information on maternal and household sociodemographic variables, smoking, parental asthma, and child's exposure to room or automobile ETS during the previous seven days was also collected. Adjusted prevalence ratios were estimated with modified Poisson regression models. RESULTS: Most sociodemographic and ETS exposure variables differed significantly by mother's country of birth. Modeled asthma prevalence was 1.95 [95% confidence interval (CI) = 1.03-3.68] times greater in children of United States-born mothers than children of Mexico-born mothers. This difference persisted after known asthma risk factors were controlled for, including parental asthma, socioeconomic and demographic variables, and child ETS exposure. Children's recent automobile ETS exposure was associated with dry nighttime cough [adjusted prevalence ratio (PR) = 1.94, 95% CI = 1.19-3.15] and asthma (PR = 2.09; 95% CI = 0.99-4.39). CONCLUSIONS: Exposure to ETS in automobiles is an important risk factor for asthma and dry nighttime cough among Hispanic children in the southwest United States, regardless of mother's country of birth. Further research is needed to identify causes of the higher prevalence of asthma in Hispanic children of United States-born mothers.     

No fathers' names: a risk factor for infant mortality in the State of Georgia, USA

Many studies have explored maternal and infant factors as risks for infant mortality, but little attention is given to paternal factors. In Georgia, listing a father's name on the birth certificate is optional for married couples and possible after paternal acknowledgment for unmarried couples. The authors evaluated father's name reporting as a paternity measure and risk for infant mortality. Using the linked 1989-1990 birth and death certificates of singleton Georgia infants to calculate relative risks (RRs), infant mortality rates for 38,943 infants with no father's names listed were compared to rates for 178,100 with father's names listed. Compared with the rate for married women listing names, the death rates were higher for unmarried mothers not listing fathers (relative risk, RR = 2.5; 95% CI 2.3-2.7), unmarried mothers listing fathers (RR = 1.4; 95% CI 1.3-1.6), and married women not listing fathers (RR = 2.3; 95% CI 1.6-3.1). Increased risks remained after stratifying by maternal race, age, adequacy of prenatal care and medical risks; and congenital malformations, birthweight, gestational age, and small-for-gestational age. Using logistic regression to examine for effect modification and to adjust for these factors together, the adjusted relative risks for death varied across different groups without fathers' names, regardless of marital status. For example, it remained statistically higher for infants with no father listed and without effect-modifying conditions such as low birthweight (estimated RR = 2.0; 95% CI 1.6-2.4). Although these findings suggest paternal involvement, as measured by listing fathers' names, is protective against low birthweight and infant mortality, further evaluation is needed.     

Association between childhood fatal injuries and socioeconomic position at individual and area levels: a multilevel study

OBJECTIVES: To simultaneously examine the effects of area-level and individual-level socioeconomic position on fatal injuries in children <5 years of age. METHODS: A retrospective cohort study based on the national birth and death registers of Korea. 2 667 060 children born during 1995-8 were followed up from birth to the 5th birthday. Cumulative incidences of fatal injuries were calculated, and through multilevel Poisson regression models, relative risks (RRs) of incidence rate were estimated according to children's sex, father's occupation and mother's education at individual level, and deprivation and degree of urbanity at area level. RESULTS: Girls had lower risk for fatal injuries than boys (RR 0.81; 95% confidence interval (CI) 0.75 to 0.87). Compared with children with fathers in non-manual occupations, those with fathers in manual (RR 1.45; 95% CI 1.34 to 1.58) or other occupations (RR 1.35; 95% CI 1.13 to 1.62) had higher risk. Children with mothers who were high school graduates (RR 1.23; 95% CI 1.12 to 1.36) or junior school graduates (RR 1.91; 95% CI 1.66 to 2.19) had higher risk than those whose mothers were college graduates. After controlling for individual-level variables, residence in more deprived districts (RR 1.13; 95% CI 1.05 to 1.21) or non-metropolitan regions (urban RR 1.34; 95% CI 1.22 to 1.47 and rural RR 1.61; 95% CI 1.40 to 1.86) was significantly associated with increased risk. CONCLUSIONS: Both individual-level and area-level socioeconomic position influenced the risk for childhood fatal injuries. To reduce the socioeconomic inequalities and the absolute burden in Korea, universal strategies should receive priority, and special efforts in implementation should be directed towards both disadvantaged households and areas.     

Recurrence of gestational age in sibships: implications for perinatal mortality.

The authors studied the extent to which preterm birth and perinatal mortality are dependent on the gestational ages of previous births within sibships. The study was based on data collected by the Medical Birth Registry of Norway from 1967 to 1995. Newborns were linked to their mothers through Norway's unique personal identification number, yielding 429,554 pairs of mothers and first and second singleton newborns with gestational ages of 22-46 weeks, based on menstrual dates. Siblings' gestational ages were significantly correlated (r = 0.26). The risk of having a preterm second birth was nearly 10 times higher among mothers whose firstborn child had been delivered before 32 weeks' gestation than among mothers whose first child had been born at 40 weeks. However, perinatal mortality in preterm second births was significantly higher among mothers whose first infant had been born at term, compared with mothers whose firstborn child was delivered at 32-37 weeks. Since perinatal mortality among preterm infants is dependent on the gestational age in the mother's previous birth, a common threshold of 37 weeks' gestation for defining preterm birth as a risk factor for perinatal death may not be appropriate for all births to all mothers.     

中国出生缺陷高发地区出生缺陷的发生水平和流行病学特征

目的研究中国出生缺陷高发地区出生缺陷的发生水平,分析主要出生缺陷的分布和流行病学特征。方法在出生缺陷高发的山西省选择2个高发县作为调查现场,对调查地区2002年1月1日至2004年12月31日期间孕满20周及以上的所有出生人口开展了以人群为基础的出生缺陷回顾性调查。结果调查地区2002—2004年出生缺陷发生率为844.2/万,发生率位于前五位的出生缺陷包括腹股沟疝(182.2/万)、无脑儿(104.4/万)、先天性智力低下(79.4/万)、先天性心脏病(73.2/万)和脊柱裂(63.9/万),前五位出生缺陷占全部出生缺陷的60%。国内外出生缺陷统计分析一般不包括腹股沟疝、鞘膜积液、隐睾和先天性智力低下,如果不包括这四类出生缺陷,调查地区出生缺陷发生率为537.2/万,位于前五位的出生缺陷分别为无脑儿、先天性心脏病、脊柱裂、脑积水(40.5/万)和脑膨出(31.2/万)。男性出生缺陷发生率为966.2/万,明显高于女性(640.4/万)。孕产妇年龄<20岁组和>30岁组出生缺陷发生率明显高于20～24岁和25～29岁年龄组。低龄孕妇发生神经管畸形和先天性心脏病的风险甚至显著高于高龄孕妇,孕产妇年龄<20岁组神经管畸形和先天性心脏病的发生率分别是408.8/万和188.7/万,而>30岁组两类出生缺陷的发生率分别为204.8/万和91.0/万。出生缺陷发生率随着孕产次的增加而明显提高。结论中国高发地区出生缺陷的发生呈现出与其他地区不同的流行病学特征,尤其是神经管畸形异常高发。不仅是高龄孕妇,20岁以下的低龄孕妇同样是一些出生缺陷发生的高危险因素。     

Parental age, family size, and risk of multiple sclerosis

BACKGROUND: Family structure, such as having siblings, provides proxy measures for a variety of characteristics relevant to disease risk. The etiology of multiple sclerosis (MS) is not well defined and analysis of family structure may provide etiologic clues. We conducted a case-control study to examine possible associations. METHODS: Using the Swedish Inpatient Register, we identified 4443 patients with a diagnosis of MS. From the general Swedish population, using birth and death registers, we selected 24,194 controls with similar characteristics for year, county of birth, and survival until at least age at diagnosis of the matched cases. The Multi-Generation Register linked data on siblings and parents. The Census provided father's social class based on occupation. RESULTS: Having 3 or more younger siblings, compared with none, produced an adjusted odds ratio (OR) for MS (with 95% confidence interval) of 0.80 (0.70-0.92) (adjusting for number of siblings, twins, maternal and paternal age, parental MS, sex, father's social class, county and year of birth). With 3 or more older siblings, the adjusted OR was 0.83 (0.72-0.96). Different-sex twin pairs compared with singletons had an OR of 0.59 (0.37-0.95) for MS. The risk of MS increased steadily with father's age but not mother's age, up to 2.00 (1.35-2.96) for 51- to 55-year-old fathers (compared with 21- to 25-year-old fathers). CONCLUSIONS: Parents who have offspring with MS may have subtly impaired fertility. The unexpected association with paternal age may be the result of an increased risk of accumulating germ cell mutations among older men.     

Socioeconomic position in early life,birth weight,childhood cognitive function,and adult mortality. A longitudinal study of Danish men born in 1953

OBJECTIVE: To examine the relation between socioeconomic position in early life and mortality in young adulthood, taking birth weight and childhood cognitive function into account. DESIGN: A longitudinal study with record linkage to the Civil Registration System and Cause of Death Registry. The data were analysed using Cox regression. SETTING: The metropolitan area of Copenhagen, Denmark. SUBJECTS: 7493 male singletons born in 1953, who completed a questionnaire with various cognitive measures, in school at age 12 years, and for whom birth certificates with data on birth and parental characteristics had been traced manually in 1965. This population was followed up from April 1968 to January 2002 for information on mortality. MAIN OUTCOME MEASURES: Mortality from all causes, cardiovascular diseases, and violent deaths. RESULTS: Men whose fathers were working class or of unknown social class at time of birth had higher mortality rates compared with those whose fathers were high/middle class: hazard ratio 1.39 (95% CI 1.15 to 1.67) and 2.04 (95% CI 1.48 to 2.83) respectively. Birth weight and childhood cognitive function were both related to father's social class and inversely associated with all cause mortality. The association between father's social class and mortality attenuated (HR(working class)1.30 (1.08 to 1.56); HR(unknown class)1.81 (1.30 to 2.52)) after control for birth weight and cognitive function. Mortality from cardiovascular diseases and violent deaths was also significantly higher among men with fathers from the lower social classes. CONCLUSION: The inverse association between father's social class at time of birth and early adult mortality remains, however somewhat attenuated, after adjustment for birth weight and cognitive function.     

Increasing prevalence of gastroschisis in Europe 1980–2002: a phenomenon restricted to younger mothers?

Gastroschisis is an abdominal wall defect more prevalent in offspring of young mothers. It is known to be increasing in prevalence despite the general decrease in the proportion of births to young European women. We investigated whether the increase in prevalence was restricted to the high-risk younger mothers. We analysed 936 cases of gastroschisis from 25 population-based registries in 15 European countries, 1980-2002. We fitted a Bayesian Hierarchical Model which allowed us to estimate trend, to estimate which registries were significantly different from the common distribution, and to adjust simultaneously for maternal age, time (in grouped years) and the random variation between registries. The maternal age-standardised prevalence (standardised to the year 2000 European maternal age structure) increased almost fourfold from 0.54 [95% Credible Interval (CrI) 0.37, 0.75] per 10,000 births in 1980-84 to 2.12 [95% CrI 1.85, 2.40] per 10,000 births in 2000-02. The relative risk of gastroschisis for mothers <20 years of age in 1995-2002 was 7.0 [95% CrI 5.6, 8.7]. There were geographical differences within Europe, with higher rates of gastroschisis in the UK, and lower rates in Italy after adjusting for maternal age. After standardising for regional variation, our results showed that the increase in risk over time was the same for mothers of all ages--the increase for mothers <20 years was 3.96-fold compared with an increase of 3.95-fold for mothers in the other age groups. These findings indicate that the phenomenon of increasing gastroschisis prevalence is not restricted to younger mothers only.     

A temporary increase of down syndrome among births of young mothers in Norway: An effect of risk unrelated to maternal age?

The Medical Birth Registry of Norway carries out a population-based surveillance of birth defects on a routine basis. An increased proportion of newborn with Down syndrome was seen among children of young mothers during 1985-1986. Three alternative explanations were considered: a first representing a maternal age specific effect, a second based on a general increase in a subgroup of cases caused by factors not related to maternal age, and a third based on the assumption that a particular birth cohort of young women was carrying a high risk. As 1987 and 1988 showed very low proportions in all age groups, the last explanation was considered less likely. Statistical modeling was used to explore which of the two remaining explanations of the temporary increase was the more likely. The observed changes were compatible with a change in the occurrence of a group of maternal age-independent Down syndrome cases, from 4.59 per 10,000 in 1973-1984 and again in 1987-1988 to a temporary high of 7.68 per 10,000 in 1985-1986. However, the possibility of an age specific change only among young mothers could not be ruled out.     

Certificates of live birth: analysis of completion in the city of Ribeir?o Preto, S?o Paulo, Brazil]

The study aims to identify the frequency with which certificates of live birth are filled out and to analyze the data they provide. To gather the data, the authors used a model birth certificate filled out by research assistants based on information obtained from the reports on mothers and newborns. This information was then compared to data contained in the official birth certificates available in the Information Technology Division of the Municipal Health Department. The sample consisted of 911 certificates of live birth from July 1996 in the ten maternity wards of the city of Ribeir?o Preto. Data analysis showed that frequency of completion of birth certificates differs by hospital, involving both physicians and administrative personnel. The authors identified a high level of agreement in the data, i.e., over 90% in 13 of 18 variables compared in the birth certificates and in half of the hospitals investigated. The disagreement occurred especially with respect to data on the number of children per mother, number of prenatal visits, mother's schooling, and father's name.     

妊娠期糖尿病的危险因素研究

目的：探讨妊娠期糖尿病（GDM）的危险因素及2型糖尿家族史对GDM发病的影响。方法：对1999年10月至2001年2月产前检查新诊断的及产科病房中已诊断的GDM患85例及177例健康对照孕妇进行单因素,多因素logistic回归分析及对数线性模型分析,探讨各因素对GDM发病的影响。结果：多因素logistic回归分析结果提示,影响GDM发病且有统计学意义的因素为孕前肥胖、2型糖尿病家族史,孕妇出生体重,年龄,高甘油三酯及体育锻炼,对数线性模型分析结果显示,父母亲患2型糖尿病均与GDM发病有关。GDM先证母亲糖尿病患率为9．41％,与GDM先证父亲糖尿病患病率（8．24％）比较,差别无显意义。结论：孕前肥胖、2型糖尿病家族中,孕妇低出生体重,年龄,高甘油三酯为GDM的危险因素,体育锻炼为保护因素,父母亲患2型糖尿病均为GDM危险因素,未发现母亲患糖尿病对孕妇患GDM的危险性影响大于父亲。     

Indoor air pollution exposure and lower respiratory infections in young Gambian children

In a rural population-based cohort study of approximately 500 Gambian children under five years old followed for one year, incidence of acute lower respiratory infections (ALR) was related to various risk factors including parental smoking and regular carriage on the mother's back while cooking, a proxy measure for exposure to smoke from cooking fires. Two statistical analyses using a 'child-weeks at risk' approach were carried out, including and excluding multiple disease episodes in the same child. Weekly surveillance for ALRI found 75 episodes in 62 children. Stratified analyses using both approaches suggested father's smoking, and, for girls only, carriage on the mother's back while cooking and being part of a polygamous family were the main risk factors associated with infection: when multiple episodes occurring in the same child were excluded, not having a health card was an additional risk factor in children over a year old. Multiple logistic regression modelling of data from both approaches, including each of these risk factors and sex, age, village and season, suggested father's smoking, carriage on the mother's back while cooking and being part of a polygamous family increase risk of ALRI, the latter two for girls only. The analysis excluding multiple episodes in the same child also suggested that not having a health card is a risk factor for children aged 1-5 years. The difficulties in interpreting these findings are discussed.     

Young motherhood and infant hospitalization during the first year of life.

We studied the relationship of young maternal age with infant hospitalization using data from the National Longitudinal Survey of Youth for 3,130 infants born between 1979 and 1983 to mothers aged 14-25 years. Data on the mothers were first collected in 1979 and yearly thereafter. Data on their children were collected starting in 1982. Logistic regressions of infant hospitalization rates were estimated for first and second and higher births. The odds of infant hospitalization during the first year of life increased with decreasing maternal age, even with adjustment for sociodemographic characteristics, preventive health-care practices, and newborn health status, factors hypothesized to explain the maternal age effect. The maternal age relationship with hospitalization differed by birth order; among second and higher births, the odds of hospitalization was increased only for infants of mothers aged 20-22 years. Male infants, infants with a first well-baby visit after the first month of life, with birth weights between 1501 and 2500 g, and with nursery stays longer than 1 week also had increased odds of hospitalization. Ethnicity, grandmother's education, poverty status, mother's school enrollment, and family composition were not related to the odds of hospitalization, nor was smoking during pregnancy when adjustment was made for birth weight and length of nursery stay.     

Prevalence of birth defects and parental work in Singapore live births from 1994 to 1998: a population-based study

The aims of the study were to assess the prevalence of birth defects (BDs) among different occupational groups and non-working parents, and to identify possible risk factors associated with BDs in Singapore live births born between 1 January 1994 and 31 December 1998. To do this, information on live births (from the Singapore National Registry of Births and Deaths) and BD cases [from the National Birth Defects Register (NBDR)] was obtained from 1 January 1994 to 31 December 1998. There were a total of 237 755 live births in Singapore between 1 January 1994 and 31 December 1998. Over the same period, 3293 cases of BDs were reported to the NBDR, giving an overall rate of 13.9 per 1000 live births. A downward trend with time was noted. Of the live born with BDs in this series, 36.7% presented with multiple anomalies. The overall occurrence of malformation (per 1000 live births) among working versus non-working mothers was 13.4 versus 14.2, respectively, and 13.8 for working fathers compared with 16.8 for non-working fathers. Parents in the occupational group 'Legislators, Senior Officers & Managers' had the lowest prevalence rates of congenital anomalies (9.4 per 1000 for mothers and 10.3 per 1000 for fathers), while the 'Agricultural & Fishery Workers' had the highest rates (40.0 per 1000 for mothers and 23.4 per 1000 for fathers). However, the very small number of workers in this latter group makes the rate unreliable. The prevalence of BDs in Singapore is comparable to those in other countries. Parental work per se is not correlated with BDs.     

珠海市1.5～3岁孤独症谱系障碍患病率及危险因素研究

目的 了解珠海市1.5～3岁孤独症谱系障碍(Autism Spectrum Disorders, ASD)的患病率及相关危险因素。方法 随机抽取在珠海市生活的1.5～3岁儿童共5 500人, 使用自编问卷和改良婴幼儿孤独症筛查量表中文修订版进行初筛;对结果阳性者由专科医师根据临床观察及儿童孤独症评定量表评定结果进行确诊;最后统计分析ASD患儿的患病率及危险因素。结果 本次调查ASD患病率为29.45/10⁴(95%CI为15.41/10⁴～44.86/10⁴), 均为典型孤独症患儿, 男女比例为6∶1。ASD组与非ASD组在性别、家庭收入、父母文化程度、母孕期间是否服用特殊药物(避孕药物、抗精神病药物、抗癫痫病药物等)、母孕期间是否补充叶酸、父亲年龄的分布上存在明显不同, 差异有统计学意义(P<0.05);回归分析结果显示家庭收入偏低、母孕期间服用特殊药物、母孕期间未补充叶酸及出生时父亲年龄偏高(>35岁)或偏低(<25岁)等可能为ASD的危险因素。结论 珠海市1.5～3岁ASD患病率低于国内外的报道水平;母亲怀孕时避免使用特殊药物、积极补充叶酸, 避免父亲年龄过高或过低可能有助于降低ASD患病率。     

Fathers of children born to young urban mothers

Fathers of babies born to a sample of urban mothers younger than 18 at delivery ranged in age from 14-50 and were, on average, 2-4 years older than the mothers. Among the adolescent women who had given birth to their first child, 28 percent of the partners of black women and 45 percent of the partners of white women were 20 years of age or older. The educational attainment of the fathers was very low, particularly among older whites. At approximately 15 months after the child's birth, 36 percent of the fathers were neither in school nor working. Three-quarters of the pregnancies among the young white mothers and 95 percent of those among the black mothers were unplanned, but only six percent of the white mothers and 16 percent of the black mothers were using a contraceptive at the time of conception. Only 16 percent of the fathers were living with or married to the mother of their child at 15 months after birth. About 90 percent of the fathers had spent time with their child during that period, but frequency of contact declined markedly with time. Overall, 20 percent of the fathers had children by other women.     

Area deprivation,individual factors and low birth weight in England: is there evidence of an “area effect”?

OBJECTIVE: To explore the relationship between low and very low birth weights, mother's age, individual socioeconomic status and area deprivation. DESIGN: Analysis of the incidence of low and very low birth weights by area deprivation, maternal age, social class of household and estimated income. SETTING: England 1996-2000. SUBJECTS: 2 894 440 singleton live births and the 10% sample of these births for which parents' individual-level socioeconomic measures were coded. RESULTS: Social class, estimated household income, lone-parenthood and mother's age were all associated with the risk of low and very low birth weight. Even when controlling for these individual level factors, area income deprivation was significantly associated with low and very low birth weight (p<0.00). For low birth weight there was a significant interaction between area income deprivation and mother's age. For very young mothers, the area effect was non-significant (p<0.37). For older mothers, particularly those aged 30-34 years, it was stronger (p<0.00). As a result, mothers aged <18 years, although at relatively high risk of low birth weight irrespective of area income deprivation, were actually at slightly lower risk than mothers aged >40 years in the most deprived areas. CONCLUSIONS: For all but very young mothers, there seems to be a negative effect on birth weight from living in areas of income deprivation, whatever their individual circumstances.