Alcohol consumption among first-time mothers and the risk of preterm birth: a cohort study.

PURPOSE: Our aim was to explore the association between alcohol consumption, before and during pregnancy, and the risk of preterm birth among 46,252 primiparous mothers. METHODS: We obtained information on alcohol consumption from questionnaire responses at pregnancy week 15 from the prospective, observational Norwegian Mother and Child Cohort Study. Data on preterm birth, categorized as delivery before gestation week 37, were retrieved from the Medical Birth Registry of Norway. RESULTS: Among the participants, 91% consumed alcohol before pregnancy and fewer than 20% reported consuming alcohol during pregnancy. The adjusted odds ratio (aOR) for preterm birth associated with prepregnancy alcohol consumption was 0.81 (95% confidence interval [CI], 0.70-0.95). We did not find a risk reduction for overall drinking during pregnancy, aOR = 1.03 (95% CI, 0.90-1.19). However, dose-response analyses showed tendencies toward adverse effects when drinking 1-3 times per month during the first 15 weeks of pregnancy, aOR = 1.51 (95% CI, 1.14-2.00). CONCLUSIONS: We did not find any effects of alcohol consumption during pregnancy, whereas pre-pregnancy drinking was associated with reduced risk of preterm birth. Residual confounding may have influenced the risk estimates, especially before pregnancy, as nondrinkers have lower socioeconomic status and well-being than drinkers.

Low to Moderate Average Alcohol Consumption and Binge Drinking in Early Pregnancy: Effects on Choice Reaction Time and Information Processing Time in Five-Year-Old Children.

BACKGROUND: Deficits in information processing may be a core deficit after fetal alcohol exposure. This study was designed to investigate the possible effects of weekly low to moderate maternal alcohol consumption and binge drinking episodes in early pregnancy on choice reaction time (CRT) and information processing time (IPT) in young children. METHOD: Participants were sampled based on maternal alcohol consumption during pregnancy. At the age of 60-64 months, 1,333 children were administered a modified version of the Sternberg paradigm to assess CRT and IPT. In addition, a test of general intelligence (WPPSI-R) was administered. RESULTS: Adjusted for a wide range of potential confounders, this study showed no significant effects of average weekly maternal alcohol consumption during pregnancy on CRT or IPT. There was, however, an indication of slower CRT associated with binge drinking episodes in gestational weeks 1-4. CONCLUSION: This study observed no significant effects of average weekly maternal alcohol consumption during pregnancy on CRT or IPT as assessed by the Sternberg paradigm. However, there were some indications of CRT being associated with binge drinking during very early pregnancy. Further large-scale studies are needed to investigate effects of different patterns of maternal alcohol consumption on basic cognitive processes in offspring.

Reduced risk of pre-eclampsia with organic vegetable consumption: results from the prospective Norwegian Mother and Child Cohort Study.

OBJECTIVE: Little is known about the potential health effects of eating organic food either in the general population or during pregnancy. The aim of this study was to examine associations between organic food consumption during pregnancy and the risk of pre-eclampsia among nulliparous Norwegian women. DESIGN: Prospective cohort study. SETTING: Norway, years 2002-2008. PARTICIPANTS: 28 192 pregnant women (nulliparous, answered food frequency questionnaire and general health questionnaire in mid-pregnancy and no missing information on height, body weight or gestational weight gain). MAIN OUTCOME MEASURE: Relative risk was estimated as ORs by performing binary logistic regression with pre-eclampsia as the outcome and organic food consumption as the exposure. RESULTS: The prevalence of pre-eclampsia in the study sample was 5.3% (n=1491). Women who reported to have eaten organic vegetables 'often' or 'mostly' (n=2493, 8.8%) had lower risk of pre-eclampsia than those who reported 'never/rarely' or 'sometimes' (crude OR=0.76, 95% CI 0.61 to 0.96; adjusted OR=0.79, 95% CI 0.62 to 0.99). The lower risk associated with high organic vegetable consumption was evident also when adjusting for overall dietary quality, assessed as scores on a healthy food pattern derived by principal component analysis. No associations with pre-eclampsia were found for high intake of organic fruit, cereals, eggs or milk, or a combined index reflecting organic consumption. CONCLUSIONS: These results show that choosing organically grown vegetables during pregnancy was associated with reduced risk of pre-eclampsia. Possible explanations for an association between pre-eclampsia and use of organic vegetables could be that organic vegetables may change the exposure to pesticides, secondary plant metabolites and/or influence the composition of the gut microbiota.

Medical databases in studies of drug teratogenicity: methodological issues.

More than half of all pregnant women take prescription medications, raising concerns about fetal safety. Medical databases routinely collecting data from large populations are potentially valuable resources for cohort studies addressing teratogenicity of drugs. These include electronic medical records, administrative databases, population health registries, and teratogenicity information services. Medical databases allow estimation of prevalences of birth defects with enhanced precision, but systematic error remains a potentially serious problem. In this review, we first provide a brief description of types of North American and European medical databases suitable for studying teratogenicity of drugs and then discuss manifestation of systematic errors in teratogenicity studies based on such databases. Selection bias stems primarily from the inability to ascertain all reproductive outcomes. Information bias (misclassification) may be caused by paucity of recorded clinical details or incomplete documentation of medication use. Confounding, particularly confounding by indication, can rarely be ruled out. Bias that either masks teratogenicity or creates false appearance thereof, may have adverse consequences for the health of the child and the mother. Biases should be quantified and their potential impact on the study results should be assessed. Both theory and software are available for such estimation. Provided that methodological problems are understood and effectively handled, computerized medical databases are a valuable source of data for studies of teratogenicity of drugs.

Birth weight and childhood cancer.

BACKGROUND: Leukemia incidence in childhood has been shown to increase with birth weight. The purpose of this paper is to study whether the incidence of other childhood cancers also increases with birth weight. METHODS: The Norwegian Medical Birth Registry was linked to the Norwegian Cancer Registry. The data consisted of 1.65 million children, of whom 3252 had a cancer diagnosis before age 16 years. The diagnoses were divided into 1010 leukemia cases, 870 cancer cases of the central nervous system (CNS), and 1370 remaining cancers. RESULTS: The increase in hazard rate for all cancers with a 1 kg increase in birth weight was 1.23 (95% confidence interval = 1.14-1.32) after adjustment. For leukemia the increase was 1.29 (1.14-1.47), for CNS cancers 1.07 (0.93-1.23), and for the remaining cancer diagnoses 1.29 (1.16-1.40). CONCLUSIONS: There seems to be a general relationship between heavier birth weight and cancer incidence in childhood.

Suspected retinopathies in Norwegian optometric practice with emphasis on patients with diabetes: a cross-sectional study.

BACKGROUND: The scope of optometry differs worldwide. In Norway the vast majority of optometrists perform ophthalmoscopy as part of their routine examinations. The aim of this study was to describe the frequency of suspected retinopathies in patients seen for routine optometric examination and to determine how optometrists deal with these patients. METHODS: 212 optometrists participated in a questionnaire survey and a practice registration during November 2004 - May 2005. In the practice registration, details for 20 consecutive patient encounters were recorded. Data were analysed by chi-square tests and multiple logistic regression. RESULTS: All optometrist stated that ocular history taking was an integrated part of their routine examination, while general health and diabetes history were routinely addressed by 59% and 42% of the optometrists, respectively. During the practice registration 4,052 patient encounters were recorded. Ophthalmoscopy was performed in 88% of the patients, of which 2% were dilated fundus examinations. Retinopathy was suspected in 106 patients, of whom 31 did not report a previous history of ocular or systemic disease. Old age (75+), hypertension and diabetes strongly predicted retinopathy with odds ratio (95% CI) of 6.4 (4.2 to 9.9), 3.8 (2.4 to 6.0) and 2.5 (1.4 to 4.7), respectively. Diabetic retinopathy was seen in 10% of diabetic patients and suspected in 0.2% of patients with no established history of diabetes. Retinopathy was not confirmed in 9 out 18 patients with a history of diabetic retinopathy; seven of these had undergone laser treatment. Out of the 106 patients with findings of retinopathy, 28 were referred to an ophthalmologist or a general practitioner (GP), written reports were sent to a GP in 16 cases, ten patients were urged to contact their GP for further follow up, while 52 were considered in need of routine optometric follow up only. CONCLUSION: Optometric practice provides a low threshold setting for detecting cases of ocular disease and retinal manifestations of systemic disease in the population. At present diagnosis of retinopathy in Norwegian optometric practice is unreliable. There are potentials for improving the optometrists' routine examination, their patient management patterns and collaboration routines with medical doctors.

Optometric practice in Norway: a cross-sectional nationwide study.

PURPOSE: To describe optometric practitioners and their encountering patients. METHODS: All members of the Norwegian Association of Optometrists working in the community (n = 761) were invited to participate in a questionnaire survey; questionnaire responders (n = 508) were asked to take part in a practice registration. Data collection was carried out between November 2004 and May 2005 using a questionnaire and a practice registration form. RESULTS: Five hundred and eight optometrists responded to the questionnaire; of these 212 participated in the practice registration, in which 4052 patient encounters were recorded. All optometrists reported taking patient history in the areas of vision and ocular health; 55% asked questions about general health for all patients. More than 80% collaborated with general practitioners and ophthalmologists. The patient encounters were with 1699 men and 2216 women; 60% of patients were aged 45 years or older. Patients reported a history of ocular disease and other conditions of relevance for ocular health in 12% and 17% of encounters, respectively. One per cent had low vision [best corrected visual acuity (BCVA) < 0.33] and 2% were visually impaired (BCVA < 0.5). Ophthalmoscopy was performed for 88% of patients; dilated fundus examinations were carried out for 2%; clinical findings of cataract were reported for 11%; and retinopathy was suspected in 3%. Six per cent of patients were referred to a general practitioner or ophthalmologist. CONCLUSION: Optometrists generally collaborate with general practitioners and ophthalmologists. They take history, investigate and assess patients with ocular problems. A significant number of patients had primary or secondary ocular disease. This illustrates the role of optometrists as healthcare workers.

Maternal smoking does not affect fetal size as measured in the mid-second trimester.

BACKGROUND: Cigarette smoking during pregnancy is causally related to birthweight, but we do not know whether fetal growth restriction is a continuous process or, if not, at what stage of pregnancy it affects weight gain. MATERIAL AND METHODS: A random sample of para 1 and 2 mothers, drawn from the population of pregnant women in Bergen and Trondheim, Norway, and Uppsala, Sweden, were examined by a detailed questionnaire concerning smoking habits, menstrual history and pregnancy dating, and subjected to morphometric sonography of their fetuses in or around week 17. Of the 547 study participants, 31.9% were smokers. Gestational age was primarily determined by the last menstrual period [LMP], except in those with irregular cycles, and in 30 cases (6.6% of those with regular cycles) in whom the biparietal diameter [BPD]-determined age deviated >14 days from the LMP-based date. RESULTS: The analysis did not reveal any statistically significant differences between the fetuses of non-smokers, light smokers (0-9 cigarettes per day) and heavy (10+ cigarettes per day) smokers, regarding BPD, mean abdominal diameter [MAD] femur length [FL], and a 'body contour index': [BPD+FL]/MAD. CONCLUSION: Tobacco-induced fetal growth restriction probably begins after gestational week 17.

The rare, unilateral headaches. Vågå study of headache epidemiology.

In the Vågå study of headache epidemiology, 1838 parishioners in the age group 18-65 years were included (88.6% of the relevant population). Each individual was questioned in a face-to-face situation. In this population, a search of rare unilateral headaches was also made, in spite of their presumed rarity. Trigeminal neuralgia was present in two cases. Two individuals with SUNCT traits were observed. Hemicrania continua may have been present in one individual. Also observed were: optic neuritis (n=1), herpes zoster (n=4); a case of unilateral headache upon neck rotation (chronic paroxysmal hemicrania variant? or "forme fruste" of the neck-tongue syndrome?); masseter muscle spasm (n=1); temporo-mandibular joint dislocation (n=1); and possible carotidynia (n=3). A particularly intriguing form of headache was a unilateral, neuralgiform (?) pain, associated with ipsilateral, regular jabs and allodynia, a combination observed in eight females. A couple of conditions that entirely defy rubrication are also reported.

Low birthweight and mortality: the tendency to repeat low birthweight and its association with early neonatal and infant morbidity and mortality.

Previous studies have demonstrated the tendency to repeat gestational age and birthweight in successive pregnancies and that this tendency is associated with infant survival. Thus, newborn outcome and survival is less favourable if the gestational age and size departs from this maternal tendency. This paper aims to study diseases or conditions that might be associated with this effect. Data were provided through a linkage between three Danish health registries: the Danish Fertility Database, the National Hospital Registry, and the Registry for Preventive Medicine. Such linkage was possible due to the use of unique ID-person numbers. The study included all 8219 second-order low-birthweight (LBW) singleton Danish births, 1980-94, of whom 7811 were liveborn. It was also required that the mother's first delivery took place during that period. The analysis considered 7803 of these births; eight were excluded due to insufficient information. Of the second-order LBW children, 26% had an elder sibling who was also LBW. Early neonatal mortality of a 'non-repeat' LBW birth was 1.3 times higher than 'repeat' LBW births [53.8 vs. 41.2 per 1000; RR 1.31; 95% CI 1.03, 1.65], as was infant mortality [78.4 vs. 60.8 per 1000; RR 1.30; 95% CI 1.06, 1.56]. Also, proportionately more LBW repeat births had Apgar scores of >or=7 after 1 and 5 min. Overall, repeat second-order LBW babies weighed 68 g more than non-repeat LBW babies (P < 0.001). At term, the weight difference was 160 g higher among repeat LBW births (P < 0.001). The mean number of hospitalisations during the first year of life was lower among repeat than non-repeat LBW babies (2.30 vs. 2.46, P < 0.001), while the mean duration of stay was 23.71 vs. 23.97 days (P > 0.05). Newborn immaturity was the most common diagnosis for hospitalisation, and infections the second most common. There were no differences between repeat and non-repeat LBW births in the proportion with each diagnosis. Apart from the differences in birthweight, we were unable to explain the improved survival for repeat compared with non-repeat LBW babies. Except for differences in Apgar scores, we observed no differences in morbidity based on registered hospitalisations during infancy.

Does persistent involvement by the GP improve palliative care at home for end-stage cancer patients?

OBJECTIVE: To analyse the effect of GP home visits on the granting of a terminal declaration (TD) and on place of death. PARTICIPANTS AND DESIGN: A total of 2025 patients with cancer as the primary cause of death in the period 1997-1998, were investigated in a mortality follow-back design using the Danish Cancer Register and four administrative registers. The Danish TD can be issued by a physician for patients with an estimated prognosis of six months or less. The TD gives the right to economic benefits and increased care for the dying patient. SETTING: The island of Funen/Denmark. MAIN OUTCOME MEASURES: Main outcome--hospital death. Intermediate outcome--TD. RESULTS: A total of 38% of patients received a TD and 56% died in hospital. GP home visits in the week before TD (odds ratio (OR): 16.8; 95% CI: 8.2-34.4), as well as four weeks before TD (OR: 6.4; 95% CI: 4.5-9.2) were associated with an increased likelihood of receiving a TD. GP home visits in the group with TD (OR: 0.18; 95% CI: 0.11-0.29) and the group without TD (OR: 0.08; 95% CI: 0.05-0.13) was inversely associated with hospital death. A dose-response relationship was found in both groups. CONCLUSION: Persistent involvement by the GP is associated with improved end-of-life care for cancer patients. Provided that temporal relations are taken into account, the mortality follow-back design can be a suitable and ethical research method to highlight and monitor end-of-life cancer care.

Migraine with aura: visual disturbances and interrelationship with the pain phase. Vågå study of headache epidemiology.

In the Vågå study of headache epidemiology, 1838 or 88.6% of the available 18-65-year-old inhabitants of the commune were included. Everyone was questioned and examined personally by the principal investigator (OS). There were 178 cases of various types of visual disturbances during the migraine attack, which corresponds to 9.7% of the study group. The prevalence among females was 11.9% and among males 7.4%; female/male ratio was 1.70, as against 1.05 in the total Vågå study population. By far the most frequently occurring visual disturbance pattern was (A) 1. Visual disturbances --> 2. pain-free interlude --> 3. pain phase (in 78% of the cases). Other frequent patterns were: (B). Visual disturbances, but no pain phase (24%); and: (C) 1. Pain phase --> 2. visual disturbances (23%). Evidently, in the solitary case, there might be more than one visual disturbance pattern. The most frequently occurring solitary visual disturbances were: scintillating scotoma (62%) and obscuration (33%); but also more rare ones were identified, like anopsia, autokinesis (movement of stationary objects), tunnel vision and micropsia. Among the non-visual aura disturbances, paraesthesias and speech disturbances were the most frequent ones. The prevalence of migraine with aura seemed to be considerably higher than in similar studies. This also includes studies that have been carried out with a face-to-face interview technique.

Whiplash in individuals with known pre-accident, clinical neck status.

In whiplash studies, there may be interpretation difficulties: are post-whiplash findings, when present, a consequence of the whiplash trauma, or did they exist prior to trauma? In the Vågå headache epidemiology study (1995-1997), there was a headache history and detailed physical/neurological findings from the face/head/neck in 1838 18-65-year-old parishioners. In September 2001, four years after the Vågå study, a search through the Health Centre files divulged six cases with whiplash trauma in the intervening period. These parishioners could thus be their own controls. Two females did not develop new complaints. In the four parishioners with apparently new, subjective complaints, i.e., headache, neck pain, and a feeling of stiffness in the neck, there were corresponding findings as regards various parameters: shoulder area skin-roll test, changes in two, possible changes in two; range of motion, neck, changes in two, borderline changes in one; "features indicative of cervical abnormality" ("CF"), changes in all four; the mean, post-whiplash stage value was: 3.6+, against 1.6+ prior to accident (Vågå: only 0.93%, "CF" exceeding 3+). In the two without new complaints, the mean "CF" value was 1.0+. The number of cases is small, but the similarity of the symptoms--and signs--following whiplash injury may suggest an element of organic origin in the whiplash syndrome.

Head circumference at birth and risk of brain cancer in childhood: a population-based study.

BACKGROUND: Studies have found only a weak or no association between birthweight and brain cancer in childhood. However, previous studies have not assessed the association between head circumference at birth and brain cancer. We aimed to assess the risk of brain cancer in childhood according to head circumference at birth. METHODS: We investigated the association between incidence of brain cancer in childhood and factors recorded at birth such as head circumference, birthweight, and gestational age based on the Norwegian medical birth registry from 1978-98, linked to the Norwegian cancer registry from 1978-2002. FINDINGS: We analysed 1,010,366 individuals with 12,378,172 person-years of follow-up, from which 453 individuals aged 0-15 years were diagnosed with brain cancer. The relative risk of brain cancer was 1.27 (95% CI 1.16-1.38) per 1-cm increase in head circumference after adjustment for birthweight, gestational age, and sex. INTERPRETATION: Head circumference is positively associated with incidence of brain cancer in childhood, suggesting that brain pathology originates during fetal life.

Haemoglobin and serum ferritin in pregnancy--correlation with smoking and body mass index.

BACKGROUND: Little is known about factors which may influence haemoglobin (Hb) and ferritin levels in pregnancy. AIM: To analyse if haemoglobin and ferritin levels during pregnancy are influenced by maternal age, body mass index, cigarette smoking, and iron supplementation. METHODS: A random sample of 561 parous pregnant women were recruited from the catchment areas of three Scandinavian university hospitals. The analyses were based on 5024 haemoglobin and 1529 ferritin measures sampled from the first trimester to 42 weeks of gestation. Multilevel modelling was used to construct mean and percentile curves for haemoglobin and ferritin by gestational age. RESULTS: Women aged 25-34 years had significantly higher haemoglobin values than older and younger women. Haemoglobin values were significantly lower for women with body mass index < 19 kg/m(2) than for women with body mass index > or =19. Smokers had significantly lower haemoglobin values throughout pregnancy compared to non-smokers, with the lowest values among women who smoked 1-9 cigarettes per day. There were no similar associations between ferritin and maternal age, body mass index, or smoking. Women with iron supplementation throughout pregnancy had a higher relative increase in haemoglobin concentration toward the end of pregnancy. In non-supplemented women the decline in ferritin concentration was significantly steeper than in those who received iron supplementation. CONCLUSIONS: Haemoglobin levels during pregnancy are significantly associated with maternal age, cigarette smoking, body mass index, and iron supplementation. No such associations were found with ferritin levels, except for iron supplementation.

Population-based study of place of death of patients with cancer: implications for GPs.

BACKGROUND: A majority of patients with cancer who are seriously ill have a preference of dying at home. However, only a minority of patients actually die at home in most Western countries. AIM: To explore factors associated with place of death in an unselected population of patients with cancer. DESIGN OF STUDY: Case-control study. SETTING: County of Funen, Denmark. METHOD: Register linkage from six Danish healthcare registers. RESULTS: The GP's home visit during the last 3 months before death was inversely associated with dying in hospital (adjusted odds ratio [OR] = 0.08, 95% confidence interval [CI] = 0.06 to 0.12) and so were community nurses visiting the home (OR = 0.36, 95% CI = 0.26 to 0.48). Furthermore, being married (OR = 0.68, 95% CI = 0.56 to 0.85), and age at death of 40-65 years (OR = 0.70, 95% CI = 0.56 to 0.90) seemed to have an effect. Hospital death was associated with survival time of less than 1 month (OR = 2.27, 95% CI = 1.69 to 3.13). Type of cancer, sex, or residence (urban versus rural) were not associated with a hospital death in this multivariate analysis. CONCLUSIONS: Dying at home was, to a higher extent, associated with GP visit and, to a lesser extent, community nurse visit than with clinical and sociodemographic characteristics of patients with cancer. In our view, these findings indicate the importance of the GP in particular. To increase the opportunity to die at home, more research is needed on the role of the GP and the interface between GPs and other providers of health care at home for patients who are terminally ill with cancer.

Birth defects in children conceived by ICSI compared with children conceived by other IVF-methods; a meta-analysis.

BACKGROUND: Intracytoplasmic sperm injection (ICSI) is a method of assisted reproductive technology that involves the selection of a single sperm cell and the manual injection of this cell into the egg. The lack of relevant experimental studies, the nature of the technology involving non-natural selection of the fertilizing sperm, and possible damage to the egg have caused concern that ICSI could increase the risk of birth defects. Data from available cohort studies comparing ICSI with standard in vitro fertilization (IVF) should be combined to evaluate the risks involved with ICSI. METHODS: We reviewed more than 2500 titles and abstracts containing keywords related to ICSI and identified 22 scientific articles with data on birth defects among ICSI-births. A total of four peer-reviewed, non-overlapping prospective cohort studies provided reliable and comparable data on birth defects both for children conceived by ICSI and children conceived by standard IVF. These studies included a total of 5395 children born after ICSI. RESULTS: The pooled estimate of the risk of a major birth defect was a 1.12-fold increase after ICSI when compared with standard IVF (risk ratio = 1.12, 95% confidence interval (CI): 0.97-1.28, P = 0.12). There was no marked heterogeneity of risk ratios between these studies (P = 0.10). We found no significantly increased risks after ICSI for any of the categories cardiovascular defects, musculoskeletal defects, hypospadias, neural tube defects, or oral clefts. CONCLUSIONS: Our analysis does not indicate that the ICSI-procedure represents significant additional risks of major birth defects in addition to the risk involved in standard IVF. The data was limited, particularly on risks of specific categories of defects.

[Parents' education and infant mortality 1967-1998]. / Foreldres utdanning og spedbarnsdødelighet 1967-98.

BACKGROUND: We have examined the association between socioeconomic status and risk of infant death in Norway between 1967 and 1998. METHODS: Information from the Medical Birth Registry of Norway on all live births and infant deaths was linked to information from Statistics Norway on parents' education. There were 1,777,364 eligible live births and 15,517 infant deaths. Differences between educational-attainment groups were estimated as risk difference, relative risk, population-attributable fraction, and index of inequality ratio. RESULTS: The risk of infant death decreased in all educational-attainment groups and the level of education increased over time. For neonatal (0-27 days of life) death the risk difference between infants whose mothers had high or low education was reduced from 3.5/1000 in the 1970s to 0.9/1000 in the 1990s. The inequality ratio declined from 1.72 to 1.32 and the population-attributable fraction from 22.3 to 8.4. For risk of postneonatal (28-364 days of life) death, the difference between infants whose mothers were in high or low education brackets increased from 0.7/1000 in the 1970s to 2.0/1000 in the 1990s. The inequality ratio went up from 1.31 to 4.00 and the population-attributable fraction from 9.7 to 39.5. INTERPRETATION: Since the late 1960s, infant mortality has decreased and parental educational levels have risen. There is a higher degree of social equality with regard to risk of neonatal death, while the opposite holds for postneonatal death.

Socioeconomic status and risk of infant death. A population-based study of trends in Norway, 1967-1998.

BACKGROUND: The aim of this study was to examine the association between socioeconomic status and risk of infant death in Norway from 1967 to 1998. METHODS: Information from the Medical Birth Registry of Norway on all live births and infant deaths was linked to information from Statistics Norway on parents' education. There were 1777364 eligible live births and 15517 infant deaths. Differences between education groups were estimated as risk differences, relative risks, population attributable fractions, and index of inequality ratios. RESULTS: The risk of infant death decreased in all education groups, and the level of education increased over time. The trends differed for neonatal and postneonatal death. For neonatal death the risk difference between infants whose mothers had high and low education was reduced from 3.5/1000 in the 1970s to 0.9/1000 in the 1990s. The relative index of inequality (RII) for maternal education decreased from 1.72 to1.32. The proportion of neonatal deaths that could be attributed to <13 years of education decreased from 22.3 to 8.4. For postneonatal death the risk difference between infants whose mothers had high and low education increased from 0.7/1000 in the 1970s to 2.0/1000 in the 1990s. The RII for maternal education increased from 1.31 to 4.00. The population attributable fraction increased from 9.7 to 39.5. CONCLUSIONS: An inverse association between socioeconomic status and risk of postneonatal death persists, albeit there was a considerable reduction in risk between 1967 and 1998.

Association of head circumference at birth among sibling pairs.

The objective of the study was to estimate and compare the correlation coefficients of head circumference and weight at birth among sibling pairs. Pairs of singleton siblings were ascertained among children born in Norway to the same mother between 1978 and 1997. Head circumference, birthweight and other perinatal factors were registered in the Medical Birth Registry of Norway. Head circumference measurements were obtained for first- and second-born in 287 448 sibling pairs. The correlation coefficient of head circumference among first- and second-born siblings was 0.343 (standard error 0.002) compared with 0.477 (standard error 0.002) for birthweight. These results were similar for later-born sibling pairs and only slightly influenced by other factors such as sex, fatherhood and time between pregnancies. Sensitivity analyses showed that substantial measurement error is required to explain the lower correlation for head circumference. In conclusion, the sibling correlation of head circumference was consistently weaker than that of birthweight.