Assessment of in utero hypoxia and risk of sudden infant death syndrome

Few data are available on the role of hypoxia in sudden infant death syndrome (SIDS). The purpose of this study was to assess whether 10 antenatal factors consistent with in utero hypoxia were associated with an increased risk of SIDS. Cases and two sets of controls were chosen from the Upstate New York Live Birth Cohort for 1974 (n = 132,948). One hundred and forty-eight SIDS cases were identified, along with 114 dead controls made up of all other sudden deaths. Randomly selected live controls were frequency-matched to cases on mother's age, race, residence, parity, and infant's birthdate (n = 355). Data were collected from vital certificates (97% response), hospital delivery records (89%), and autopsy reports (100%). Odds ratios and 95% confidence intervals were calculated using Mantel-Haenszel techniques and logistic regression. Abnormal uterine bleeding was the only statistically significant (P less than 0.05) risk factor observed when dead controls were used (OR = 5.4). When live controls were used, statistically significant increases in risk were found for: placenta praevia (OR = 21.8), abruptio placentae (OR = 3.7), multiple birth (OR = 29.6), pregnancy interval less than or equal to 12 months (OR = 3.8), sexually transmitted disease (OR = 6.4), and eclampsia (OR = 17.7). These results lend support to a possible hypoxic aetiology of SIDS; however, differences by control group suggest that some factors are not specific to SIDS alone but may be risk factors for infant mortality in general.     

Labor and delivery events and risk of sudden infant death syndrome (SIDS)

The purpose of this study was to assess whether labor and delivery events were risk factors for sudden infant death syndrome (SIDS). A nested case-control design was used. From the 1974 cohort of live births for Upstate New York (exclusive of New York City), resident mothers (n = 132,948), SIDS cases, and living controls were selected. Data were abstracted from hospital delivery and vital records for 148 autopsied cases and 355 frequency-matched controls. With the use of unconditional logistic regression, no increase in SIDS risk was observed for artificial rupture of membranes, medication use during labor, induction/augmentation of labor, or anesthesia for delivery. An increased risk of SIDS was observed for labor 16 hours or more (odds ratio (OR) = 2.6, 95% confidence interval (CI) 1.1-6.5) and vaginal breech delivery (OR = 7.2, 95% CI 0.7-72.2). Significant inverse trends were observed for Apgar scores and risk of SIDS.     

Maternal smoking, low birth weight, and ethnicity in relation to sudden infant death syndrome

To determine independent effects of maternal smoking and infant low birth weight (less than 2,500 g) on risk of sudden infant death syndrome (SIDS) among different ethnic groups, the authors conducted a population-based case-control study based on the 1984-1989 Washington State birth record data. Two control groups were selected for 916 SIDS cases. The first one comprised 3,704 randomly selected controls, matched to cases by birth year, to describe the characteristics of the study population. In the second control group (n = 6,186), minorities were oversampled, by matching to cases on maternal race/ethnicity and birth year, to increase the power of analysis within each ethnic group. All subjects were classified into five groups on the basis of maternal race/ethnicity: white, black, American Indian, Asian, and Hispanic. After controlling for confounders, the authors found that maternal smoking was independently associated with SIDS among white (odds ratio (OR) = 2.2, 95% confidence interval (CI) 1.8-2.6), blacks (OR = 3.1, 95% CI 1.7-5.9), Asians (OR = 2.7, 95% CI 1.1-6.6, and Hispanics (OR = 5.5, 95% CI 1.4-22.0), but had little relation among American Indians (OR = 1.4, 95% Cl 0.9-2.4). Infant low birth weight was independently related to SIDS among whites (OR = 2.5, 95% Cl 1.8-3.4) and American Indians (OR = 5.5, 95% Cl 2.8-11.2) and to a lesser extent among blacks (OR = 1.9, 95% Cl 0.8-4.1), but not among Asians (OR = 1.1, 95% Cl 0.2-5.2) or Hispanics (OR = 1.2, 95% Cl 0.1-11.5). The misclassification that may occur because of the application of the same definition of low birth weight to all ethnic groups may be the main reason for the weaker association between infant low birth weight and SIDS among blacks and the absence of an association among Asians and Hispanics. Defining low birth weight as below population mean minus 1.96 standard deviations may provide better insight into the relation between low birth weight and SIDS. Understanding the reasons for the lack of a strong association between maternal smoking during pregnancy and SIDS among American Indians may enhance our knowledge of the etiology and pathogenesis of SIDS.     

Preconception homocysteine and B vitamin status and birth outcomes in Chinese women

BACKGROUND: The associations between homocysteine, B vitamin status, and pregnancy outcomes have not been examined prospectively. OBJECTIVE: We assessed the associations of preconception homocysteine and B vitamin status with preterm birth and birth of low-birth-weight (LBW) and small-for-gestational-age (SGA) infants in Chinese women. DESIGN: This was a case-control study of women aged 21-34 y. Preterm cases (n = 29) delivered living infants at <37 wk gestation; term controls (n = 405) delivered infants at > or =37 wk. LBW cases (n = 33) had infants weighing <2500 g; normal-birth-weight controls (n = 390) had infants weighing > or =2500 g. SGA cases (n = 65) had infants below the 10th percentile of weight-for-gestational-age; appropriate-for-gestational-age controls (n = 358) had infants above this cutoff. Nonfasting plasma concentrations of homocysteine, folate, and vitamins B-6 and B-12 were measured before conception. RESULTS: Elevated homocysteine (> or =12.4 micro mol/L) was associated with a nearly 4-fold higher risk of preterm birth (OR: 3.6; 95% CI: 1.3, 10.0; P < 0.05). The risk of preterm birth was 60% lower among women with vitamin B-12 > or =258 pmol/L than among vitamin B-12-deficient women (OR: 0.4; 95% CI: 0.2, 0.9; P < 0.05) and was 50% lower among women with vitamin B-6 > or =30 nmol/L than among vitamin B-6-deficient women (OR: 0.5; 95% CI: 0.2, 1.2; NS). Folate status was not associated with preterm birth, and homocysteine and B vitamin status were not associated with LBW or SGA status. CONCLUSIONS: Elevated homocysteine and suboptimal vitamin B-12 and B-6 status may increase the risk of preterm birth. These results need to be confirmed in larger prospective studies.     

Timing of prenatal care and risk of sudden infant death syndrome

Sudden infant death syndrome (SIDS) is the leading cause of death during post-neonatal life. Mothers whose infants succumb to SIDS are reported to initiate prenatal care later than control mothers. Previous studies have not always controlled for socioeconomic status (SES) of mothers or other potential confounders such as gestational age or birthweight of infants. The purpose of this study was to assess whether timing of prenatal care adjusted for these potential confounders was an independent risk factor for SIDS. SIDS cases (N = 148) were identified from the Upstate New York livebirth cohort for 1974 (N = 132,948) and compared to randomly selected controls (N = 355) who were frequency-matched on maternal age, race, parity and residence and infant's birth date. Data were abstracted from matched vital certificates (97% response), hospital delivery records (89% response) and selected sample of autopsy reports (100% response). Odds ratios (OR) and 95% confidence intervals (CI) were obtained using unconditional logistic regression. A significant inverse relationship was observed for number of prenatal visits and risk of SIDS; a significant direct relationship was observed between trimester prenatal care initiated and risk of SIDS. The results suggest that timing of prenatal care is important in assessing SIDS risk even after adjusting for potential confounders of early prenatal care utilization.     

Sudden infant death syndrome: seasonality and a biphasic model of pathogenesis.

STUDY OBJECTIVE--This paper examines the relationship between season, age, and the sudden infant death syndrome (SIDS). It provides a theoretical model for the pathogenesis of SIDS and uses it as a framework to consider risk factor mechanism. DESIGN--A case series analysis was used to examine season and age in relation to SIDS and seasonal pattern and age at death distribution of perinatal risk factors. SETTING--The source population for the SIDS cases in this study was all live births in the state of Tasmania, Australia, 1975 to 1987 inclusive. SUBJECTS--Cases were all infants born 1975 to 1987 who died of SIDS on whom birth notification information was available (n = 348). The live birth cohort 1980-87 (n = 55,944) was used as the control population for risk factor identification. MEASUREMENTS AND MAIN RESULTS--The median ages of death for spring, summer, autumn, and winter born infants were 115, 103.5, 91 and 78 days. Spring and summer born infants died at a significantly older median age than winter born infants. The month of birth distribution of SIDS cases did not alter significantly from a uniform, nonseasonal distribution (p greater than 0.25) but month of death was seasonally distributed (p less than 0.01). Premature and low birthweight infants died at an older median age (p less than 0.05) than term and non-low-birthweight infants. An excess of male infant deaths and infant deaths to older mothers occurred during winter (p less than 0.05). CONCLUSIONS--The pathogenesis of SIDS can be represented as a biphasic model with three pathways of risk factor operation. In this study, season influenced the age at death of SIDS infants. We propose that risk factors with a strong seasonal distribution are likely to be operating in the postnatal period.     

Sudden infant death syndrome in Australian Aboriginal and non-Aboriginal infants: an analytical comparison

Summary. Our previous research has shown that the sudden infant death syndrome (SIDS) rate for Aboriginal infants in Western Australia (WA) is markedly higher than that for non-Aboriginal infants. The aim of this study was to identify factors that may be important in explaining this disparity. A case-control study was conducted based on routinely collected data for the population of WA singleton births from 1980 to 1990 inclusive. Cases were infants bom and classified as dying from SIDS in WA (Aboriginal n = 88; non-Aboriginal n = 409). Controls were infants born in WA and not classified as dying from SIDS; 2% samples of both Aboriginal and non-Aboriginal infants were included. The risk of dying from SIDS in Aboriginal infants was 3.86 times [95% confidence interval (CI) = 2.98 to 5.02] that in non-Aboriginal infants. Statistically significant univariable risk factors for SIDS in Aboriginal infants were preterm birth, low birthweight and small-for-gestarional-age; for non-Aboriginal infants they included these factors as well as single marital status, young maternal age, parity of one or greater and male sex. Comparing Aboriginal with non-Aboriginal controls, most of the risk factors were more common in the Aboriginal population. Multiple logistic regression analysis indicated that Aboriginal infants were 1.43 times [95% CI = 1.04 to 1.95] more likely to die from SIDS than non-Aboriginal infants. Differences in the risk factor profile for Aboriginal and non-Aboriginal infants were sought using interaction terms. The only important differences were that the risk of SIDS in Aboriginal infants, unlike that in non-Aboriginal infants, appeared not to be strongly related to male sex or to single marital status. Thus, the results show that the disparity between the incidence of SIDS in the Aboriginal and non-Aboriginal populations can be explained largely, although not totally, by the high prevalence of routinely recorded risk factors in the Aboriginal population. A limitation of this study is that data on the postnatal nsk factors of prone sleeping, maternal smoking and non-breastfeeding were unavailable. The residual excess risk for Aboriginal infants may be a result of these recognised postnatal risk factors and /or other infant care practices that are not routinely recorded in our data base, or to underlying social and economic conditions. Further study of all these potential risk factors is warranted.     

Effect of marijuana use in pregnancy on fetal growth

In a prospective study of 3,857 pregnancies ending in singleton live births at Yale-New Haven Hospital, New Haven, Connecticut, in 1980-1982, 9.5% of mothers reported using marijuana (4.1% occasionally and 5.4% at least 2-3 times monthly). Among white women, regular use was associated with an increased risk of delivering a low birth weight (less than 2,500 gm) infant (odds ratio (OR) = 2.6, 95% confidence interval (CI) = 1.1-6.2) and small for gestational age infant (OR = 2.3, 95% CI = 1.3-4.1) after adjustment for other risk factors. Nonwhite marijuana users were not at further increased risk for delivering a low birth weight or small gestational age infant beyond the elevated rates of these conditions already experienced by nonwhites in general. Marijuana use was also related to preterm delivery (gestational age less than 37 weeks from last menstrual period) in white women (OR = 1.9, 95% CI = 1.0-3.9) but not nonwhite women. Occasional use was unrelated to the risk of low birth weight, small for gestational age, or preterm delivery.     

The relation between multiple births and maternal risk of breast cancer.

Data from two case-control studies conducted in New York State during 1982-1986 were used to examine the relation between multiple births and the maternal risk of breast cancer. The cases were 2,561 women between 20 and 79 years of age with a diagnosis of primary breast cancer. Controls (n = 2,616) were selected from driver's license files and matched to cases by year of birth and county of residence. The odds ratio for any multiple birth was 0.94 (95% confidence interval (CI) 0.56-1.56) in women less than 55 years of age and 0.95 (95% CI 0.62-1.46) in women aged 55-79 years. A previous study had shown a multiple last birth to be protective against breast cancer in women less than 55 years of age (odds ratio (OR) = 0.60, 95% CI 0.43-0.85). A decreased risk of breast cancer was also observed for this age group in the present study, but the magnitude of the effect was not as strong and the confidence interval included unity (OR = 0.85, 95% CI 0.43-1.68). A logistic model that controlled for age at first pregnancy, number of live births, age, and county of residence increased the odds ratio to 0.97 for a multiple last birth. The current study does not support an association between multiple births and maternal risk of breast cancer.     

Birth characteristics and subsequent risk for breast cancer in very young women

There is growing evidence that prenatal exposures may influence later breast cancer risk. This matched case-control study used linked New York State birth and tumor registry data to examine the association between birth characteristics and breast cancer risk among women aged 14-37 years. Cases were women diagnosed with breast cancer between 1978 and 1995 who were also born in New York after 1957 (n = 484). For each case, selected controls were the next six liveborn females with the same maternal county of residence. The authors found a J-shaped association between birth weight and breast cancer risk, and very high birth weight (> or =4,500 g) was associated with the greatest elevation in risk (adjusted odds ratio (OR) = 3.10, 95% confidence interval (CI): 1.18, 7.97). The association of maternal age with breast cancer risk was also J-shaped, with maternal age of more than 24 years showing a positive, linear association (adjusted OR = 1.94, 95% CI: 1.18, 3.18 for maternal age > or =35 vs. 20-24 years; p for trend = 0.02). In contrast, women born very preterm had a lower risk (adjusted OR = 0.11, 95% CI: 0.02, 0.79 for gestational age <33 vs. > or =37 weeks). These findings support a role for early life factors in the development of breast cancer in very young women.     

Prenatal and intrapartum events and sudden infant death syndrome

The purpose of this study was to evaluate specific pregnancy and labour and delivery events that may increase the risk of sudden infant death syndrome (SIDS). A matched case-control study was conducted in five counties in southern California, using California death certificate records. The sample consisted of 239 Caucasian, African-American, Hispanic and Asian mothers of SIDS infants and 239 mothers of control infants matched on sex, race, birth hospital and date of birth. Mothers participated in a detailed telephone interview and provided access to obstetric and paediatric records. More case than control mothers reported a family history of anaemia (OR=2.12, P < 0.001). Placental abruptions were strongly associated with SIDS (unadjusted OR=7.94, [95% CI 1.34,47.12]). There was an increased risk of SIDS death associated with maternal anaemia during pregnancy (OR=2.51, [95% CI 1.25,5.03]), while simultaneously adjusting for maternal smoking during pregnancy, maternal years of education and age, parity, infant birthweight, gestational age, medical conditions at birth, infant sleep position and post-natal smoking. Interactions of anaemia and prenatal smoking as well as anaemia and post-natal smoking were not statistically significant. There were no other statistically significant differences between case and control mothers for pregnancy conditions, labour and delivery events (e.g. caesarean sections, anaesthesia, forceps) or newborn complications (e.g. nuchal cord, meconium aspiration). Anaemia and placental abruptions were significantly associated with an increased risk of SIDS; both are circumstances in which a fetus may become hypoxic, thereby compromising the subsequent growth, development and ultimate survival of the infant.     

Maternal, delivery, and perinatal characteristics associated with cryptorchidism: a population-based case-control study among births in Washington State

BACKGROUND: The etiology of cryptorchidism is largely unknown. To identify maternal, perinatal, and delivery characteristics associated with cryptorchidism at birth, we conducted a population-based case-control study using Washington State birth certificates linked to birth hospitalization records. METHODS: We identified 2,395 cases of cryptorchidism among male infants born in Washington State during 1986-1996, and, for comparison, we randomly selected four controls per case (N = 9,580), frequency-matched by year of birth. RESULTS: Infant characteristics associated with cryptorchidism included low birth weight (OR = 1.5; 95% CI = 1.3-1.8), small size for gestational age (OR = 1.9; 95% CI = 1.6-2.2), and breech presentation (OR = 1.7; 95% CI = 1.4-2.1). In addition to cryptorchidism, cases were more likely to have another type of congenital malformation (OR = 3.7; 95% CI = 3.2-4.2), particularly digestive (OR = 6.8; 95% CI = 3.7-12.7) or genitourinary (OR = 4.1; 95% CI = 3.0-5.6). Maternal and pregnancy characteristics associated with cryptorchidism included nulliparity (OR = 1.2; 95% CI = 1.1-1.3), maternal smoking during pregnancy (OR = 1.2; 95% CI = 1.1-1.4), and the following pregnancy complications: oligohydramnios (OR = 1.8; 95% CI = 1.3-2.6), placental abnormality (OR = 1.3; 95% CI = 1.0-1.8), and pregnancy-induced hypertension (OR = 1.6; 95% CI = 1.4-1.9). Odds ratios were similar when the analysis was restricted to term infants. CONCLUSIONS: These findings suggest that factors affecting fetal growth and development may increase the risk of cryptorchidism.     

Preterm delivery and age of SIDS death

PURPOSE: The aim of the study is to (i) reexamine risk factors for sudden infant death syndrome (SIDS) and (ii) describe the relationship between length of gestation and age at death from SIDS. METHODS: To evaluate risk factors for SIDS, we used multivariable logistic regression and included maternal demographic characteristics, maternal health and behavioral factors, and infant characteristics, including fetal growth, using US national linked birth and death files from 1996 to 1998. We used multivariable linear regression with mean postnatal age of death as the outcome of interest, controlling for the factors listed (referent length of gestation, 40 to 41 weeks). RESULTS: The crude SIDS rate was 0.7 deaths/1000 live births (8199 deaths). Length of gestation was a strong risk factor for SIDS, with the adjusted odds ratio (OR) greatest at shorter gestations: 28 to 32 weeks (OR, 2.9; 95% confidence interval, 2.6-3.2). Infants with gestations of 22 to 27 and 28 to 32 weeks died at mean ages of 20.9 (SD = 0.8) and 15.3 (SD = 0.5) weeks, respectively (p < or = 0.002). Term infants (40 to 41 weeks) died of SIDS at an adjusted mean age of 14.5 (SD = 0.4) weeks. CONCLUSIONS: Preterm birth continues to be a strong risk factor for SIDS after controlling for fetal growth. With increasing gestational age, mean age of SIDS death decreases considerably, with the postnatal age of death of very preterm infants 6 weeks later than that of term infants.     

The epidemiology of sudden infant death in upstate New York: II: birth characteristics.

This study describes the epidemiology of sudden infant death syndrome (SIDS) among infants born during 1974 to upstate New York residents. Birth certificate characteristics for 184 SIDS cases are compared with those of 417 infants dying from other causes in the same age range, 7-365 days. The results confirm the following as infant risk factors: fall or winter birth, low birthweight for gestational age, twin birth, and live birth order three or more. Maternal risk factors include: age under 20, abnormal uterine bleeding during pregnancy, late initiation of prenatal care, less than 12 years of education and single marital status. The increased risk for mothers who first gave birth in their teens and for second-born twins has not been previously reported. The evidence that SIDS babies are small for gestational age, that twins, especially the second born, and babies whose mothers experienced abnormal uterine bleeding during pregnancy are all at increased risk of SIDS suggests that perinatal stress leading to hypoxia is one of the components that determine the risk of SIDS.     

The development of a model for predicting infants at high risk of sudden infant death syndrome in Tasmania

A statutory 'Notification of Birth' form, containing obstetric and perinatal information, has been routinely collected for Tasmanian deliveries since 1974. For the period 1980 to 1984, birth notification data was collected for over 99% of Tasmanian deliveries. This data was examined for the 130 cases of sudden infant death syndrome (SIDS) that occurred from 1980 to 1984 and for 610 controls. It was then used to construct an at-birth scoring system to predict infants at higher risk of SIDS in the postneonatal period. A predictive model of the relative risk of SIDS was developed by fitting a binomial/logistic generalised linear model to the binary 1980-1984 case control data with birth variables used as predictors. The final predictive model contained five variables (maternal age, infant sex, birth weight, month of birth and feeding practice) and had a sensitivity of 62% and specificity of 73%. The model was then tested on independent birth cohorts from 1985 and 1986 and found to have a sensitivity of 47% and specificity of 77%. The risk of SIDS in the group of infants classified as high risk was 7.9 per 1000 live births and in the group at low risk it was 2.5 per 1000 live births. In addition, the model predicted 74% of neonatal deaths occurring during these 2 years. This compares well with other predictive models developed elsewhere. The predictive model will be used to identify infants at high risk for SIDS in a prospective cohort study.     

Association between gestational diabetes and pregnancy-induced hypertension

Gestational diabetes and pregnancy-induced hypertension are common, and their relation is not well understood. The authors conducted a population-based case-control study using 1992-1998 Washington State birth certificate and hospital discharge records to investigate this relation. Consecutive cases of pregnancy-induced hypertension were divided into four groups based on International Classification of Diseases, Ninth Revision codes: eclampsia (n=154), severe preeclampsia (n=1,180), mild preeclampsia (n=5,468), and gestational hypertension (n=8,943). Cases were compared with controls who did not have pregnancy-induced hypertension (n=47,237). Gestational diabetes was more common in each case group (3.9% in eclamptics, 4.5% in severe preeclamptics, and 4.4% in both mild preeclamptics and those with gestational hypertension) than in controls (2.7%). After adjustment for body mass index, age, ethnicity, parity, and prenatal care, gestational diabetes was associated with increased risk of severe preeclampsia (odds ratio (OR)=1.5, 95% confidence interval (CI): 1.1, 2.1), mild preeclampsia (OR=1.5, 95% CI: 1.3, 1.8), and gestational hypertension (OR=1.4, 95% CI: 1.2, 1.6). Gestational diabetes was more strongly associated with pregnancy-induced hypertension among women who received less prenatal care (OR=4.2 for eclampsia and OR=3.1 for severe preeclampsia, p<0.05 for both) and among Black women (OR for eclampsia and preeclampsia together=3.9, p<0.05).     

Perinatal mortality associated factors in a general hospital of Chiapas, Mexico

OBJECTIVE: To identify socioeconomic, gynecological-obstetric and fetal factors associated with perinatal mortality. METHODS: A matched case-control study was carried out. Cases were newborns (born live or dead) that were born and died between 28 weeks gestation and 7 days of life. Controls were live newborns between 28 weeks gestation and 7 days of life. A total of 99 cases and 197 controls were studied. Data were obtained from the corresponding medical charts. Statistical analysis was performed using Stata 6.0 software. RESULTS: Mean maternal age was 24.82 years and mean newborn age was 37.78 weeks gestation with an average birth weight of 2,760 grams. Factors associated with perinatal mortality were: father's occupation as a farmer (adjusted odds ratio (OR)=3.31; 95% CI=1.26-8.66); high obstetric risk index (adjusted OR=10.57; 95% CI=2.82-39.66), cesarean birth (adjusted OR=2.75; 95% CI=1.37-5.51), five or more prenatal visits (adjusted OR=4.43; 95% CI=1.86-10.54) and preterm fetal maturity indices (PEG, APG, GEG) (adjusted OR=9.20; 95% CI=4.39-19.25). CONCLUSIONS: The risk factors associated with perinatal mortality found in the study are consistent with the findings reported in the international literature. These results show that prevention and control measures should be implemented to identify at risk pregnant women in order to lower perinatal mortality.     

Maternal placental abnormality and the risk of sudden infant death syndrome

To determine whether placental abnormality (placental abruption or placental previa) during pregnancy predisposes an infant to a high risk of sudden infant death syndrome (SIDS), the authors conducted a population-based case-control study using 1989-1991 California linked birth and death certificate data. They identified 2,107 SIDS cases, 96% of whom were diagnosed through autopsy. Ten controls were randomly selected for each case from the same linked birth-death certificate data, matched to the case on year of birth. About 1.4% of mothers of cases and 0.7% of mothers of controls had either placental abruption or placenta previa during the index pregnancy. After adjustment for potential confounders, placental abnormality during pregnancy was associated with a twofold increase in the risk of SIDS in offspring (odds ratio = 2.1, 95% confidence interval 1.3-3.1). The individual effects of placental abruption and placenta previa on the risk of SIDS did not differ significantly. An impaired fetal development due to placental abnormality may predispose an infant to a high risk of SIDS.     

Risk factors for neonatal and post-neonatal mortality in the Central-West region of Brazil: linkage between live birth and infant death data banks

This article focused on risk factors for neonatal and post-neonatal mortality by linking live births and infant death records. The study was conducted in the municipality of Goiania, in the Central-West region of Brazil. A total of 20,981 live births and 342 infant deaths constitute the retrospective cohort. Neonatal and post-neonatal mortality risks were estimated in this cohort study of live births by logistic regression. In the neonatal period, the highest ORs were for delivery in public hospitals (OR = 2.28; 95% CI 1.57-3.32), pre-term neonates (OR = 8.94; 95% CI 5.85-13.67), and low birth weight (OR = 8.92; 95% CI 5.77-13.79). Cesarean delivery appeared as a protective factor (OR = 0.58; 95% CI 0.43-0.78). For post-neonatal mortality, the highest ORs were for illiterate mothers (OR = 6.25; 95% CI 1.25-31.27), low birth weight (OR = 3.12; 95% CI 1.67-5.84), and delivery in public hospitals (OR = 2.65; 95% CI 1. 13-6.23). The linkage identified socioeconomic variables that were more important risk factors for post-neonatal than neonatal mortality.     

In utero exposure to steroid contraceptives and survival during infancy.

A cohort study was conducted in Chiang Mai, northern Thailand, in 1,431 children of women who had used the injectable contraceptive Depo-Provera (The Upjohn Company, Kalamazoo, Michigan), 565 children of women who had used oral contraceptives during pregnancy, and a group of 2,307 control infants with no hormonal contraceptive exposures. In follow-up interviews, information was obtained on stillbirths and deaths. Cause of death was ascertained by interview, death certificate, or medical record, and underlying causes of death were ascribed by a panel. The children exposed in utero to Depo-Provera had higher neonatal and infant mortality rates (44.3 and 62.9 per 1,000 live births, respectively) than did the controls (19.8 and 29.1 per 1,000 live births). Mortality in infants exposed in utero to oral contraceptives was intermediate between that in the other two groups. Adjustment by logistic regression showed no significantly increased risk of mortality among infants exposed to oral contraceptives, but the odds ratio for death was significantly increased with Depo-Provera exposures due to accidental pregnancy (odds ratio (OR) = 1.8 (95% confidence interval (Cl) 1.1-3.0) for neonatal deaths; OR = 2.0 (95% Cl 1.3-3.2) for infant deaths). Adjustment for low birth weight reduced the risks, suggesting that low birth weight may act as an intermediate determinant of Depo-Provera-associated mortality. Among the accidental pregnancies with Depo-Provera, there was a relation between shorter injection-to-conception intervals, when maternal blood levels of the drug are high, and an increased risk of mortality. The odds ratios for neonatal mortality were 2.5 (95% Cl 1.1-5.7), 2.1 (95% Cl 1.0-4.6), and 0.9 (95% Cl 0.4-2.4) for injection-to-conception intervals of less than or equal to 4, 5-8, and greater than 9 weeks, respectively. Adjustment for low birth weight reduced these risks. Chi-square tests for trend were highly significant. Similar associations were also observed between Depo-Provera accidental pregnancies and risks of low birth weight. Thus, infants from accidental pregnancies that occur 1-2 months after a 150-mg Depo-Provera injection may be at increased risk for low birth weight and death. However, the attributable risk is low, because such pregnancies are uncommon.