Risk factor patterns for cryptorchidism and hypospadias.

To evaluate the hypothesis of a common etiology for cryptorchidism and hypospadias, we conducted two case-control studies nested in a nationwide cohort in Sweden, using record linkage between the Inpatient and Birth Registries. Cases were 2,782 and 1,220 boys operated for cryptorchidism or hypospadias, respectively. Five matched controls per case were randomly selected. Pregnancy and perinatal data were prospectively recorded in the Birth Registry. Data were modeled through conditional logistic regression. Both cryptorchidism (odds ratio (OR) = 2.22) and hypospadias (OR = 2.75) were positively associated with other congenital malformations and inversely with maternal parity (OR = 0.77 and 0.52, respectively, for parity 4+ compared with primiparae). There is evidence that being born small-for-gestational-age and before the 33rd gestational week have a greater-than-additive effect with respect to both cryptorchidism (OR = 6.19 vs 1.72 expected) and hypospadias (OR = 4.39 vs 2.60 expected) compared with non-small-for-gestational-age boys born at term. Hypospadias was positively associated with severe preeclampsia (OR = 2.11). We conclude that the etiologies of the two conditions are partly shared.     

The impact of maternal smoking during pregnancy on delivery outcome

BACKGROUND: Maternal smoking during pregnancy is associated with pre-term birth, intrauterine growth retardation, a small head circumference, a low Apgar score at 5 min and stillbirths and neonatal deaths. This study was undertaken in order to investigate the impact of maternal smoking during pregnancy when all these outcomes were considered. METHODS: With the use of the Swedish Medical Birth Registry, infants in any one of the above mentioned outcome groups were selected from 1,413,811 infants born between 1983 and 1996 with known smoking exposure in early pregnancy. Confounders such as year of birth, maternal age, parity and educational level were controlled for. The attributable risk of maternal smoking on the various negative delivery outcomes was obtained by application of the risk estimates to population counts. RESULTS: The present study confirmed the associations between maternal smoking and the miscellaneous outcomes mentioned above with high significance. The odds ratios (with 95% confidence intervals) for maternal smoking (< 10 cigarettes/day and > or = 10 cigarettes/day) for any one of the outcomes were 1.39 (1.37-1.41) and 1.65 (1.62-1.68) respectively (dose-response p < 0.001). The number of attributable cases caused by maternal smoking was estimated at 15,000, which represents 9% of all cases and 1% of all infants born in Sweden during the study period. CONCLUSION: Maternal smoking during pregnancy accounts for a substantial part of various negative delivery outcomes.     

Reproductive outcomes among hairdressers

OBJECTIVES: The present study aimed at examining the possible risk of working as a hairdresser during pregnancy in relation to reproductive outcomes. METHODS: The Swedish Medical Birth Register, which includes almost every infant born in Sweden, has, since 1983, collected information prospectively about occupation in early pregnancy. This information is given at the first visit to a prenatal center. During the period 1983-2001, 12 046 infants were born to female hairdressers working either full- or part-time during early pregnancy. For comparison, all other deliveries during the same period were used in which the mother had worked either part-time or full-time. RESULTS: The full-time hairdressers more often had intrauterine growth-retarded infants (ie, small for gestational age) as compared with referents with a corresponding worktime [adjusted odds ratio (OR) 1.20, 95% confidence interval (95% CI) 1.06-1.36]. The pattern was similar for part-time hairdressers (adjusted OR 1.16, 95% 0.93-1.46). The fraction of malformations did not differ from those among the referents. The gender ratio for the infants of hairdressers was similar to that for the overall Swedish population. CONCLUSIONS: The findings concerning infants small for their gestational age in the present study is in accordance with previous findings. The reason for these findings remains unknown. Studies with more-specific exposure information during pregnancy are needed.     

Maternal occupation and congenital heart defects: a case-control study

Summary This paper reports a Swedish analysis of the possible effect of maternal occupation on the occurrence of congenital heart defects. The analysis included 3324 infants (1108 cases and 2216 controls) born during the period 1982–1986. Information on maternal occupation was retrieved using two sources: the 1985 census and the Medical Birth Registry. A comparison between these two sources using the information on mothers of 756 infants born in 1986 showed a good concordance although 11% of the women were reported with a different employment status. No association appeared between the type of maternal occupation and the occurrence of infant congenital heart defects although some odds ratios were slightly above 1.     

Recurrence risk for major congenital heart defects in Sweden: A registry study

During the period 1981–1986, 1605 infants presenting a major congenital heart defect (CHD) were identified in Sweden. Using the personal identification numbers of the mothers, 1507 of them could be linked to the Medical Birth Registry and two controls were selected for each infant. For this total of 4521 infants, 2686 postoccurrence sibs born during the period 1981–1989 were identified from the Medical Birth Registry. The tendency to have one or more sibs was higher among cases than among controls and was correlated to the life status of the proband. This tendency did not vary according to the type of CHD when controlling for life status. The prevalence at birth of CHD was almost four times higher among sibs of CHD infants than among sibs of normal infants. The tendency to have a sib with an extracardiac malformation did not differ between CHD probands and normal probands. The importance of only including births occurring after the proband when evaluating recurrence risks is stressed. © 1994 Wiley-Liss, Inc.     

Cryptorchidism and maternal alcohol consumption during pregnancy

BACKGROUND: Prenatal exposure to alcohol can adversely affect the fetus. We investigated the association between maternal alcohol consumption during pregnancy and cryptorchidism (undescended testis) among newborn boys. METHODS: We examined 2,496 boys in a prospective Danish-Finnish birth cohort study for cryptorchidism at birth (cryptorchid/healthy: 128/2,368) and at 3 months of age (33/2,215). Quantitative information on alcohol consumption (average weekly consumption of wine, beer, and spirits and number of binge episodes), smoking, and caffeine intake was obtained by questionnaire and/or interview once during the third trimester of pregnancy, before the outcome of the pregnancy was known. For a subgroup (n = 465), information on alcohol consumption was obtained twice during pregnancy by interviews. RESULTS: We investigated maternal alcohol consumption both as a continuous variable and categorized. The odds for cryptorchidism increased with increasing weekly alcohol consumption. After adjustment for confounders (country, smoking, caffeine intake, binge episodes, social class, maternal age, parity, maturity, and birth weight) the odds remained significant for women with a weekly consumption of five or more alcoholic drinks (odds ratio = 3.10; 95% confidence interval, 1.05-9.10). CONCLUSIONS: Regular alcohol intake during pregnancy appears to increase the risk of congenital cryptorchidism in boys. The mechanisms for this association are unknown. Counseling of pregnant women with regard to alcohol consumption should also consider this new finding.     

School attainment of children who had a single umbilical artery at birth

Lilja M. School attainment of children who had a single umbilical artery at birth. Paediatric and Perinatal Epidemiology 2010; 24: 166–170. To the best of our knowledge, this is the first registry study of school achievements among children born with a single umbilical artery (SUA). A total of 1600 infants born with SUA during 1983–86 were studied. We linked the Swedish Medical Birth Registry with the Swedish School Registry, which contains the school grades of all children in Sweden when leaving compulsory school. Risks were estimated as odds ratios (OR) using the Mantel‐Haenzel procedure, after adjustment for four potential confounders: year of birth, maternal age, parity and maternal education. There was a 60% excess of children born with SUA who did not complete compulsory school after removal of infants born preterm, small‐for‐gestational age and low Apgar score (OR = 1.60 [95% confidence interval 1.28, 2.00]). When sports and the three core school subjects (mathematics, English and Swedish) were studied, there was an increased risk for ‘not passed’ in all subjects except sport and a slight decrease in the probability of achieving ‘passed with distinction or excellence’. In the three core subjects there was an association with gender, boys with SUA being more likely to have ‘not passed’ than girls. In conclusion the children born with SUA are more likely than children born with three vessels to show impaired school achievements.     

Maternal smoking during pregnancy: a comparison between concurrent and retrospective self-reports

Retrospective reports of smoking in pregnancy are of importance for clinical or scientific purposes. Careful analyses of stability and accuracy of recalled behaviour are, therefore, needed. In 1998, the mothers of 2369 pre-teens born in Sweden retrospectively reported their smoking behaviour during the first trimester of the index pregnancy. We matched these reports with those recorded by midwives at the beginning of the index pregnancy, using information from the Swedish Medical Birth Registry. Using this registry as gold standard, the sensitivity and specificity of the retrospective reports containing any smoking were 83.9% and 92.8% respectively, but the sensitivity was low for daily smoking, 56.0%. Of the 222 discordant reports, 19.0% were due to mothers recalling daily smoking which was not reported at the time of pregnancy, and 42% were due to failure to recall smoking reported at the time of pregnancy, while the remaining 39% retrospectively reported occasional smoking, whereas they were registered as non-daily smokers when pregnant. Retrospective recall of pregnancy smoking is fairly stable over time.     

Risk factors for cryptorchidism]

Objectives: To identify the main risk factors for cryptorchidism in southeast Spain, and their possible association with environmental factors.Methods: In this retrospective case-control study, the target population consisted of babies born in the University of Granada Hospital (UGH) in Granada, Spain, between 1 January 1992 and 31 December 1999, both inclusive. All boys from the target population aged 1 year or more diagnosed at the Pediatric Urology or Endocrinology Services of the UGH as having cryptorchidism (n = 70) were included, and a random sample of 144 baby boys born without cryptorchidism or any other related genitourinary abnormality or disease formed the control group. The mother's hospital record in the obstetrics clinic was checked to record information on potential risk factors, such as residence (specific health care district), parents' occupation, obstetric antecedents, diseases during pregnancy, gestational age at birth, birth weight and type of delivery. To search for associations between cryptorchidism and each of the variables we calculated crude and adjusted odds ratios with unconditional logistic regression analysis.Results: Low gestational age at birth ( 37 weeks) and cesarian section were significantly associated with cryptorchidism. We also found an association with residence of the mother in the Costa-Alpujarra health care district, but its magnitude decreased when the association was adjusted for the father's occupation in agriculture. This last factor was also associated with cryptorchidism, although the association was not statistically significant.Conclusions: Our findings are consistent with those of other studies, except for the absence of association between low birth weight and cryptorchidism. Geographic variations in our study population suggested that environmental factors possibly related with farm work are involved in cryptorchidism.     

Harsh social conditions and perinatal survival: an age-period-cohort analysis of the World War II occupation of Norway.

OBJECTIVES. The hypothesis was tested that unfavorable social conditions are associated with poor perinatal survival through direct effects on pregnancy or, more indirectly, through effects on mothers born under such conditions. The occupation of Norway by Nazi Germany was used as a period of social hardship. METHODS. Data from Norwegian vital statistics and the Medical Birth Registry were used to describe perinatal mortality during World War II and also a generation later, among babies born to mothers who had themselves been born during the war. Logistic regression was used to identify a possible cohort effect among mothers born in 1940 through 1944 compared with mothers born before or after that period. RESULTS. Harsh conditions in Norway during the occupation increased childhood mortality. However, perinatal mortality declined during that period. Likewise, no adverse effect was seen on the survival of babies born to mothers who had themselves been born during the war (odds ratio = 1.00; 95% confidence interval = 0.96, 1.04). CONCLUSIONS. We find no evidence that wartime conditions in Norway impaired perinatal survival, either directly or through an effect on women born during the war. These data underscore how little is known about the ways that social conditions influence perinatal mortality.     

Prenatal risk factors for cryptorchidism: a record linkage study

Using data from the Oxford Record Linkage Study (ORLS), we conducted a case–control study to examine prenatal risk factors for cryptorchidism. We identified 1449 boys born during 1970–86 for whom there was a record of an orchidopexy during 1970–87. Up to eight controls were matched to each case on year of birth and hospital or place of delivery. For each boy and his mother we extracted abstracts of maternity and general hospital records from the ORLS. Low birthweight (trend P  < 0.001), low social class (trend P  < 0.001), breech presentation (relative risk 1.67; 95% confidence interval [CI] 1.16, 2.41), pre-eclampsia (1.17 [1.00, 1.37]), artificial feeding (1.22 [1.04, 1.45]) and episiotomy (1.13 [1.00, 1.27]) were identified as independent risk factors for cryptorchidism. Gestational age was not independently associated with cryptorchidism after adjusting for birthweight ( P  = 0.33), and this observation suggested that some cryptorchid boys may have suffered from intra-uterine growth retardation. Low birthweight, breech presentation and pre-eclampsia may have in common poor placental function and impaired fetal growth, which may be causes of cryptorchidism.     

Maternal smoking, alcohol consumption, and caffeine consumption during pregnancy in relation to a son's risk of persistent cryptorchidism: a prospective study in the Child Health and Development Studies cohort, 1959-1967

The Child Health and Development Studies is a > or =40-year follow-up of 20,754 pregnancies occurring between 1959 and 1967 in California. There were 84 cases of undescended testes at birth persisting to at least age 2 years among 7,574 liveborn sons whose mothers were interviewed in early pregnancy. Cases were matched to three controls on birth year and race. Compared with mothers of controls, mothers of cryptorchid boys consumed more caffeine during pregnancy (odds ratio = 1.4, 95% confidence interval: 1.1, 1.9 for an interquartile range equivalent to three cups of coffee per day) but were not more likely to smoke or drink alcohol when all behaviors were considered together. Other maternal and perinatal risk factors were not significantly associated with persistent cryptorchidism and did not confound the association with caffeine.     

A retrospective cohort study of stroke onset: implications for characterizing short term effects from ambient air pollution

Background

Androgens are crucial for normal testicular descent. Studies show that some pesticides have estrogenic or antiandrogenic effects, and that female workers exposed to pesticides have increased risk of having a boy with cryptorchidism. The main objective of the present study was to investigate whether pregnant women exposed to pesticides due to their work in horticulture experience excess risk of having sons with cryptorchidism.

Methods

We conducted a cohort study of pregnant women working in horticulture using four cohorts including one cohort established with data from the departments of occupational medicine in Jutland and Funen and three existing mother-child cohorts (n = 1,468). A reference group was established from the entire Danish population of boys born in the period of 1986-2007 (n = 783,817). Nationwide Danish health registers provided information on birth outcome, cryptorchidism diagnosis and orchiopexy. The level of occupational exposure to pesticides was assessed by expert judgment blinded towards outcome status. Risk of cryptorchidism among exposed horticulture workers compared to the background population and to unexposed horticulture workers was assessed by Cox regression models.

Results

Pesticide exposed women employed in horticulture had a hazard ratio (HR) of having cryptorchid sons of 1.39 (95% CI 0.84; 2.31) and a HR of orchiopexy of 1.34 (0.72; 2.49) compared to the background population. Analysis divided into separate cohorts revealed a significantly increased risk of cryptorchidism in cohort 2: HR 2.58 (1.07;6.20) and increased risk of orchiopexy in cohort 4: HR 2.76 (1.03;7.35), but no significant associations in the other cohorts. Compared to unexposed women working in horticulture, pesticide exposed women had a risk of having sons with cryptorchidism of 1.34 (0.30; 5.96) and of orchiopexy of 1.93 (0.24;15.4).

Conclusions

The data are compatible with a slightly increased risk of cryptorchidism in sons of women exposed to pesticides by working in horticulture.     

Maternal smoking in pregnancy: does it increase the risk of childhood cancer?

Experimental studies show that some compounds in tobacco smoke are transplacental carcinogens, but epidemiological data on maternal smoking and childhood cancer are inconclusive. Using the national Swedish Medical Birth and Cancer Registries, the incidence of cancer was followed through 1987 in a cohort of 497,051 children born 1982-1987 for whom information was available on maternal smoking at 2-3 months of pregnancy. A total of 327 cancers appeared including 198 solid tumours and 129 cancers of the lymphatic and haematopoietic system. The overall relative risk for cancer in children with mothers reporting smoking during pregnancy was 0.99 (95% confidence interval (CI): 0.78-1.27). Corresponding risks for solid tumours and cancers of the lymphatic/haematopoietic system were 0.96 (0.70-1.32) and 1.04 (0.71-1.52), respectively. There was no consistent increase in risk for cancer of different sites or in relation to number of cigarettes smoked per day.     

Mortality of twins and singletons by gestational age: a varying-coefficient approach

This study used data from the Swedish Medical Birth Registry between 1982 and 1995 to address the question of whether there is higher mortality in twins in relation to singletons of the same gestational age and to examine the optimal gestational age range for twins. A "varying-coefficient approach" was adopted to estimate the gestational age-specific relative and absolute risks of mortality in twins and singletons, adjusting for size at birth and risk factors of short gestational duration. The models showed that twins born between 29 and 37 weeks of gestation had lower mortality than did singletons of the same gestational age. Twins born at older gestational age had higher mortality than did their singleton counterparts, because longer gestational duration was more advantageous to singletons than to twins. Without adjustment for size at birth, there was an upturn of mortality in twins born after 38 weeks. It is postulated that twins have better health than singletons initially, but they could not enjoy the benefit of a longer gestational duration as much as singletons could. The optimal gestational age for twins appeared to be 37-39 weeks according to neonatal and infant mortality.     

Maternal smoking in pregnancy as a determinant of rheumatoid arthritis and other inflammatory polyarthropathies during the first 7 years of life

OBJECTIVES: Personal smoking and gender are determinants of adult rheumatoid arthritis. We assessed the independent and joint effects of maternal smoking in pregnancy and gender on the development of rheumatoid arthritis and other inflammatory polyarthropathies (RA&IP, ICD-9 code 714) in particular juvenile rheumatoid arthritis (JRA, ICD-9 code 714.3) in the first 7 years of life in a cohort of Finnish children born in 1987. METHODS: We identified 58 841 singleton births from the Finnish Medical Birth Registry and followed-up on them through other nationwide registries for 7 years. The birth registry provided categorical information on the mother's smoking during pregnancy: no smoking as a reference, low exposure (<10 cigarettes per day) and high exposure (>10 cigarettes per day). RESULTS: There were 75 cases of RA&IP yielding an incidence rate of 18.5 per 100 000 person-years. Of these, 31 were classified as JRA with an incidence rate of 7.6 per 100 000 person-years. In logistic regression, both the risks of RA&IP (adjusted odds ratio (OR) 2.10; 95% confidence interval (CI) 1.30-3.40) and JRA (3.03; 1.36-6.76) were increased in girls. High exposure to tobacco smoke increased the risks of RA&IP (2.57; 1.13-5.89) and JRA (2.98; 0.95-8.78) in girls, but not in boys. The adjusted ORs for girls with heavy exposure were 4.64 (1.94-11.07) for RA&IP and 6.76 (2.00-22.9) for JRA compared with unexposed boys. CONCLUSION: This is an original finding of a potential effect of foetal exposure to tobacco smoke on the risks of RA&IP and JRA in girls.     

Survival of infants born with Down's syndrome: 1980-96

The improved life expectancy of people with Down's syndrome as a result of the greater availability of surgery and advances in medical care has been widely documented. However, there has been no evaluation of survival in the Australian Down's syndrome population since the 1980s. This study aimed to evaluate the changes in survival from birth in cases of Down's syndrome notified to the Birth Defects Registry in Western Australia. Babies born with Down's syndrome between 1980 and 1996 (inclusive) and registered with the Birth Defects Registry were studied. Survival status was obtained in several ways. Cases were stratified into three cohorts for comparison. Survival curves were constructed using the methods of Kaplan and Meier. For infants born during 1980-96, survival to 1 year is now > 91%, and 85% can expect to survive until the age of 10 years. Although survival in those with heart disease showed improvement over the period studied, overall this was still a strong predictor of mortality. Survival in Aboriginal children with Down's syndrome was significantly poorer than in non-Aboriginal children, mirroring the pattern in the general population. Mortality was greater in females and in those with a low birthweight. There was no statistically significant difference in the survival between those born in metropolitan and in rural areas. There has been a considerable improvement in survival of infants born with Down's syndrome in Western Australia. This improvement is similar to findings in recent international studies. The difference in survival between Aboriginal and non-Aboriginal children is particularly disturbing. These findings are useful for both clinicians and families who need to plan for the long-term care of these children.     

Post-neonatal mortality in Norway 1969-95: a cause-specific analysis

BACKGROUND: We recently reported increased social inequality for post-neonatal death. The aim of the present study was to investigate the association between socioeconomic status and cause-specific post-neonatal death. METHODS: All 1,483,857 live births recorded in the Medical Birth Registry of Norway from 1969-95 with information on parents' education were included. During the post-neonatal period (from 28 to 364 days of life) 4,464 infants died. Differences between education groups were estimated as risk differences, relative risks, population attributable fractions, and relative index of inequality. RESULTS: The major causes of death were congenital conditions, sudden infant death syndrome (SIDS), and infections. Post-neonatal mortality declined from 3.2/1,000 in the 1970s to 1.9/1,000 in the 1990s, mainly due to reduced mortality from congenital conditions. The absolute risk for SIDS increased by 0.51/1,000 in the same period among infants whose mothers had low education, while it decreased by 0.56/1,000 for those whose mothers had high education. The relative risk for SIDS among infants whose mothers had low education increased from 1.02 in the 1970s to 2.39 in the 1980s and 5.63 in the 1990s. Among infants whose fathers were not recorded in the Birth Registry, the absolute risk of SIDS increased by 0.79/1,000 from the 1970s to the 1990s. CONCLUSIONS: Increased social inequality for post-neonatal death was primarily due to increases in the absolute and relative risks of SIDS among infants whose mothers have low education. Social inequality widened during the study period for SIDS and deaths caused by infections.     

A quality study of a medical birth registry

A quality control study was made of the Swedish Medical Birth Registry. This registry used one mode of data collection during 1973-1981 and another from 1982 onwards. The number of errors in the register was checked by comparing register information with a sample of the original medical records, and the variability in the use of diagnoses between hospitals was studied. Different types of errors were identified and quantified and the efficiency of the two methods of data collection evaluated.     

A birth weight for gestational age standard based on data in the Swedish Medical Birth Registry, 1985–1989

Birth weight curves according to gestational length are presented based on data from more than 480,000 singleton births, registered in the Medical Birth Registry and with gestational age based on ultrasound examinations in the majority of cases. Curves were constructed from the most common weights in each week (modes) for each sex and standard deviations were estimated under the assumption of a fixed coefficient of variation, the size of which was estimated from 40 weeks infants. This methodology makes it possible to construct graphs for specific subgroups of infants: such graphs for boys and girls for primiparous and multiparous women are given in the paper.