Birth Weight Of Full-term Infants Research Articles

A scalable two-stage Bayesian approach accounting for exposure measurement error in environmental epidemiology.

Accounting for exposure measurement errors has been recognized as a crucial problem in environmental epidemiology for over two decades. Bayesian hierarchical models offer a coherent probabilistic framework for evaluating associations between environmental exposures and health effects, which take into account exposure measurement errors introduced by uncertainty in the estimated exposure as well as spatial misalignment between the exposure and health outcome data. While two-stage Bayesian analyses are often regarded as a good alternative to fully Bayesian analyses when joint estimation is not feasible, there has been minimal research on how to properly propagate uncertainty from the first-stage exposure model to the second-stage health model, especially in the case of a large number of participant locations along with spatially correlated exposures. We propose a scalable two-stage Bayesian approach, called a sparse multivariate normal (sparse MVN) prior approach, based on the Vecchia approximation for assessing associations between exposure and health outcomes in environmental epidemiology. We compare its performance with existing approaches through simulation. Our sparse MVN prior approach shows comparable performance with the fully Bayesian approach, which is a gold standard but is impossible to implement in some cases. We investigate the association between source-specific exposures and pollutant (nitrogen dioxide [NO2])-specific exposures and birth weight of full-term infants born in 2012 in Harris County, Texas, using several approaches, including the newly developed method.

Analysis of adverse late-term pregnancy outcomes after cervical cold knife conization

Objective: To investigate the effects of cervical cold knife conization (CKC) on preterm delivery, other pregnancy complications and neonatal outcomes, and explore the relationship between preterm delivery risk and the depth and volume of conization. Methods: The clinical data and pregnancy outcomes of 272 women who underwent CKC in Peking Union Medical College Hospital from January 2002 to March 2018 (conization group) and 1 647 pregnant women who gave birth in Peking Union Medical College Hospital during January to December 2019 (control group) were collected. The preterm delivery, premature rupture of membranes, other pregnancy complications and neonatal outcomes of the two groups were compared, and the relationship between the depth and volume of conization and the risk of preterm delivery in postoperative singleton pregnancy was analyzed. Results: (1) There were no significant differences between the two groups in delivery age, parity, proportion of singleton pregnancy, proportion of assisted reproductive technology (all P>0.05). (2) The rate of preterm delivery in the conization group was significantly higher than that in the control group [14.8% (39/264) vs 5.7% (91/1 589); χ2=28.397, P<0.001]. There were still significant differences in preterm delivery rates between the two groups at <34 weeks and 34-37 weeks (all P<0.01). There was no significant difference in the incidence of premature rupture of membrane between the two groups [23.5% (62/264) vs 23.4% (372/1 589); χ2=0.001, P=0.979], but the incidence of preterm premature rupture of membrane in the conization group was significantly higher than that in the control group [11.4% (30/264) vs 2.2% (35/1 589); χ2=56.132, P<0.001]. (3) The rate of cesarean section in the conization group was higher than that in the control group [59.6% (162/272) vs 38.8% (639/1 647); χ2=41.377, P<0.001]. The birth weight of preterm infants in the conization group was significantly higher than that in the control group [(2 409±680) vs (2 150±684) g; t=2.184, P=0.030]. However, there were no statistically significant differences in the incidence of gestational diabetes mellitus, hypertensive disorders in pregnancy, the birth weight of full-term infants, incidence of small for gestational age infant and neonatal intensive care unit admission rate between the two groups (all P>0.05). (4) The preterm delivery rates of coning depth >15 mm, cone size ≥2 cm3 and cone size <2 cm3 were higher than that in the control group (all P<0.05). When the coning depth ≤15 mm, the preterm delivery rate in the conization group was higher than that in the control group, but there was no significant difference (P=0.620). The rate of preterm delivery of pregnant women with coning depth >15 mm was significantly higher than those with coning depth ≤15 mm (RR=3.084, 95%CI: 1.474-6.453; P=0.001). There was no significant difference in the preterm delivery rate between pregnant women with cone size >2 cm3 and those with cone size ≥2 cm3 (RR=1.700, 95%CI: 0.935-3.092; P=0.077). Conclusion: The risk of preterm delivery and preterm premature rupture of membranes in subsequent pregnancies are increased after cervical CKC, and the risk of preterm delivery is positively correlated with the depth of cervical coning.

Effects of preterm birth and birth weight on developmental delays of children aged 12-36 months

Background: Early childhood is a critical period for the development of cognitive, linguistic, social, and motor abilities. Due to the importance of early detection of developmental delays in children, this study aims to investigate the effect of preterm birth and birth weight on the developmental skills among children aged 12-36 months. Materials and Methods: In this cohort study, 125 children of 12 to 36 months of age from Khorramabad, Iran, were evaluated in three groups, i.e. preterm group (59 children), low birth weight group and term infants group (21 children), and finally children with average birth weight and term infants group (45 children). This evaluation was carried out using the Ages &amp; Stages Questionnaires-Third Edition in five developmental areas. Five models of logistic regression were separately used for modeling the effect of the “age and birth weight of children”. The collected data were analyzed in SPSS v.22 software using logistic regression analysis, where the significance level was 0.05. Results: According to the findings related to child screening, the percentage of developmental delay in at least one area was 49.6%, where the highest and lowest rates of delay were 15.2% and 6.4% in fine motor and problem-solving skills, respectively. Moreover, 9.6% of the children were abnormal in communication skills, and 9.6% and 8.8% of the children were bnormal in gross motor skills and personal-social skills respectively. Based on the logistic regression method, the relationships between “the age and birth weight of children” and the state of communication skill development (P=0.235), fine motor skills (P=0.125) and personal-social skills (P=0.307) were insignificant but noticeable. Conclusion: Low birth weight in full-term infants is a risk factor for delayed communication and fine motor skills, while preterm birth is a risk factor for delayed personal-social skills. Preterm birth and low birth weight are risk factors for developmental delays in children, which require early screening to diagnose and prevent their future complications.

Serum Perfluorooctanoic Acid and Perfluorooctane Sulfonate Concentrations in Relation to Birth Outcomes in the Mid-Ohio Valley, 2005–2010

Background: Previous research suggests perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) may be associated with adverse pregnancy outcomes.Objective: We conducted a population-based study of PFOA and PFOS and birth outcomes from 2005 through 2010 in a Mid-Ohio Valley community exposed to high levels of PFOA through drinking-water contamination.Methods: Women provided serum for PFOA and PFOS measurement in 2005–2006 and reported reproductive histories in subsequent follow-up interviews. Reported singleton live births among 1,330 women after 1 January 2005 were linked to birth records (n = 1,630) to identify the outcomes of preterm birth (< 37 weeks gestation), pregnancy-induced hypertension, low birth weight (< 2,500 g), and birth weight (grams) among full-term infants.Results: We observed little or no evidence of association between maternal serum PFOA or PFOS and preterm birth (n = 158) or low birth weight (n = 88). Serum PFOA and PFOS were both positively associated with pregnancy-induced hypertension (n = 106), with adjusted odds ratios (ORs) per log unit increase in PFOA and PFOS of 1.27 (95% CI: 1.05, 1.55) and 1.47 (95% CI: 1.06, 2.04), respectively, but associations did not increase monotonically when categorized by quintiles. Results of subanalyses restricted to pregnancies conceived after blood collection were consistent with the main analyses. There was suggestion of a modest negative association between PFOS and birth weight in full-term infants (–29 g per log unit increase; 95% CI: –66, 7), which became stronger when restricted to births conceived after the blood sample collection (–49 g per log unit increase; 95% CI: –90, –8).Conclusion: Results provide some evidence of positive associations between measured serum perfluorinated compounds and pregnancy-induced hypertension and a negative association between PFOS and birth weight among full-term infants.Citation: Darrow LA, Stein CR, Steenland K. 2013. Serum perfluorooctanoic acid and perfluorooctane sulfonate concentrations in relation to birth outcomes in the Mid-Ohio Valley, 2005–2010. Environ Health Perspect 121:1207–1213; http://dx.doi.org/10.1289/ehp.1206372

Impact of smoking exposure change on infant birth weight among a cohort of women in a prenatal smoking cessation study.

Despite the known harmful effects of smoking during pregnancy, the highly addicted find it difficult to quit. Decreased smoking may be regarded as a means of harm reduction. There is limited information on the benefits of smoking reduction short of quitting. This study used salivary cotinine to assess the impact of change in smoking exposure on birth weight in full-term infants. In a prenatal smoking cessation study, smoking status was validated by saliva cotinine at baseline and end of pregnancy (EOP). Salivary cotinine ≥15 ng/ml defined active smoking. Based on salivary cotinine, women were grouped as nonsmoking/quit, light exposure (<150 ng/ml), and heavy exposure (≥150 ng/ml) at baseline and EOP. EOP and baseline smoking status were stratified to form smoking exposure change groups. Mean birth weight was compared among those who quit, reduced, maintained, and increased. Smoking cessation was associated with a 299 g increase in birth weight compared with sustained heavy smoking, p = .021. Reduced exposure from heavy to light was associated with a 199 g increase in birth weight compared with sustained heavy exposure, a 103 g increase compared with increased exposure, and a 63 g increase compared with sustained light exposure. Differences among continuing smokers were not statistically significant. Although not statistically significant, the increase in infant birth weight associated with reduction from heavy to light exposure suggests potential for benefit. The only statistically significant comparison was between quitters and sustained heavy smokers, confirming that smoking cessation should remain the goal for pregnant women.

A restrição do crescimento fetal influencia a composição corporal na idade escolar?

OBJECTIVE: To assess the influence of low birth weight in full-term infants on body composition at school age. METHOD: This is a cross-sectional study nested in a cohort of 375 infants recruited at birth between 1993 and 1994 in the state of Pernambuco, Brazil. At 8 years of age, the body composition of 213 children from this cohort was assessed by measurement of triceps and subscapular skinfold thickness and mid upper arm circumference. Multivariable linear regression analysis was used to identify the influence of low birth weight, socioeconomic condition, maternal nutritional status, and child morbidity on triceps skinfold thickness. RESULTS: Mean triceps and subscapular skinfold thickness, mid upper arm circumference, and upper arm muscle and fat areas were lower in children born at term with low weight than in those with appropriate birth weight. However, these differences were not statistically significant. Multivariable linear regression analysis showed that the relative majority of variance in triceps skinfold thickness (12.3%) was explained by socioeconomic variables, particularly per capita family income (9.1%), followed by anemia and past hospitalization (which, together, explained 5.6% of variance) and maternal body mass index, which contributed toward 2.4% of this variance. Low birth weight had no influence on triceps subcutaneous fat deposition in this age group. CONCLUSION: Socioeconomic factors and a history of morbidity had a greater influence on body composition than low birth weight in schoolchildren born at term.

Does fetal growth restriction influence body composition at school age?

To assess the influence of low birth weight in full-term infants on body composition at school age. This is a cross-sectional study nested in a cohort of 375 infants recruited at birth between 1993 and 1994 in the state of Pernambuco, Brazil. At 8 years of age, the body composition of 213 children from this cohort was assessed by measurement of triceps and subscapular skinfold thickness and mid upper arm circumference. Multivariable linear regression analysis was used to identify the influence of low birth weight, socioeconomic condition, maternal nutritional status, and child morbidity on triceps skinfold thickness. Mean triceps and subscapular skinfold thickness, mid upper arm circumference, and upper arm muscle and fat areas were lower in children born at term with low weight than in those with appropriate birth weight. However, these differences were not statistically significant. Multivariable linear regression analysis showed that the relative majority of variance in triceps skinfold thickness (12.3%) was explained by socioeconomic variables, particularly per capita family income (9.1%), followed by anemia and past hospitalization (which, together, explained 5.6% of variance) and maternal body mass index, which contributed toward 2.4% of this variance. Low birth weight had no influence on triceps subcutaneous fat deposition in this age group. Socioeconomic factors and a history of morbidity had a greater influence on body composition than low birth weight in schoolchildren born at term.

Ambient Air Pollution and Birth Weight in Full-Term Infants in Atlanta, 1994–2004

BackgroundAn emerging body of evidence suggests that ambient levels of air pollution during pregnancy are associated with fetal growth.ObjectivesWe examined relationships between birth weight and temporal variation in ambient levels of carbon monoxide, nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone, particulate matter ≤ 10 μm in diameter (PM10), ≤ 2.5 μm (PM2.5), 2.5 to 10 μm (PM2.5–10), and PM2.5 chemical component measurements for 406,627 full-term births occurring between 1994 and 2004 in five central counties of metropolitan Atlanta.MethodsWe assessed relationships between birth weight and pollutant concentrations during each infant’s first month of gestation and third trimester, as well as in each month of pregnancy using distributed lag models. We also conducted capture-area analyses limited to mothers residing within 4 miles (6.4 km) of each air quality monitoring station.ResultsIn the five-county analysis, ambient levels of NO2, SO2, PM2.5 elemental carbon, and PM2.5 water-soluble metals during the third trimester were significantly associated with small reductions in birth weight (−4 to −16 g per interquartile range increase in pollutant concentrations). Third-trimester estimates were generally higher in Hispanic and non-Hispanic black infants relative to non-Hispanic white infants. Distributed lag models were also suggestive of associations between air pollutant concentrations in late pregnancy and reduced birth weight. The capture-area analyses provided little support for the associations observed in the five-county analysis.ConclusionsResults provide some support for an effect of ambient air pollution in late pregnancy on birth weight in full-term infants.

Ambient Air Pollution and Birth Weight in Full-Term Infants in Atlanta, 1994-2004

ISEE-0430 Background and Objective: An emerging body of evidence suggests ambient levels of air pollution during pregnancy are associated with fetal growth. Methods: We used vital records data to construct a retrospective cohort of 406,627 full-term births occurring between 1994 and 2004 in five central counties of metropolitan Atlanta, USA. We examined the relationship between birth weight and temporal variation in ambient levels of carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), PM10 (particulate matter <10 μm in diameter), PM2.5 (particulate matter <2.5 μm in diameter) and speciated PM2.5 measurements. Daily pollutant levels in five-county Atlanta were characterized using a population-weighted spatial average of air quality monitors in the study area. Daily concentrations were then averaged over the time period corresponding to each infant's third trimester. We also conducted capture-area analyses limited to mothers residing within four miles (6.4 km) of each air quality monitoring station. Linear regression models included control for seasonal and long-term time trends, gestational week, maternal education, maternal marital status, maternal age, maternal tobacco use, race and ethnicity, and parity. Results: In the five-county analysis, ambient levels of NO2, SO2, PM2.5 elemental carbon and PM2.5 water-soluble metals were significantly associated with small reductions in birth weight in full-term infants (−4 to −16 grams per interquartile range [IQR] increase in pollutant concentrations). The capture-area analyses provided little evidence of harmful effects of air pollution, but confidence intervals were wide. Conclusion: Results provide limited support for an effect of ambient air pollution in the third trimester on birth weight in full-term infants.

Could elective cesarean sections influence the birth weight of full-term infants?

There are no studies on birth weights among full-term infants born by means of elective cesarean section. We aimed to study this in private and public hospitals. Retrospective study at Universidade Federal do Triângulo Mineiro, Uberaba, Brazil. Data were collected from the municipal medical birth register of Uberaba from January to December 2000. The data obtained (maternal age, type of delivery, number of prenatal care visits and birth weight, from full-term pregnancy) from the university hospital (UH), which is a tertiary hospital that only attends patients within the National Health System (SUS), were compared with data from four private hospitals (PHs) that attend health insurance plans and private patients. Student's t test, chi2 test and multiple logistic regression were used for statistical analysis, with the significance level set at p < 0.05. In the PHs, 1,100 out of 1,354 births (81.2%) were by cesarean section and in the UH, 373 out of 1,332 (28%). Birth weight increased significantly in association with increasing numbers of prenatal care visits, except for cesarean section cases in PHs. Birth weights among vaginal delivery cases in PHs were greater than in the UH (p < 0.05), but this was not observed among cesarean section cases. Multiple logistic regression showed that there was greater risk of low birth weight in PHs (odds ratio: 2.33; 95% confidence interval: 1.19 to 4.55). Elective cesarean section performed in PHs may be associated with low birth weight among full-term infants.

Asthma medication use in pregnancy and fetal growth

Given the high prevalence of asthma in pregnancy, it is important to understand the relationship between asthma medications and fetal growth in the context of appropriate treatment. This study examines the effect of inhaled corticosteroids, systemic corticosteroids, and beta(2)-agonists on fetal growth in 654 infants born to women with asthma compared with 303 infants born to controls without asthma. Subjects for this prospective study were enrolled throughout North America between 1998 and 2003 and followed up by the Organization of Teratology Information Services. Incidence of small for gestational age (SGA) infants and mean birth size measures were compared among groups. Mean birth weight of full-term infants born to mothers who used systemic corticosteroids (3373 g) was lower than in the beta(2)-agonist group (3552 g) and controls without asthma (3540 g; P < .05) after adjustment for other risk factors. However, no differences in the incidence of SGA for weight were observed among groups. Adjusted mean birth length was slightly shorter in the systemic steroid group compared with controls (P=.02). Incidence of SGA for length and head circumference and mean head circumference did not vary among groups (P>.05). The treatment of asthma with systemic corticosteroids resulted in a deficit of about 200 g in birth weight compared with controls and exclusive beta(2)-agonist users and no increased incidence of SGA. These results suggest that asthma management with beta(2)-agonists and/or inhaled corticosteroids during pregnancy does not impair fetal growth, whereas systemic corticosteroids have a minimal effect which should be weighed against the necessity to control severe asthma.

Safety of Haloperidol and Penfluridol in Pregnancy

To assess the safety of the butyrophenone neuroleptics haloperidol and penfluridol in pregnancy. The rate of major anomalies was compared between a cohort of pregnant women counseled for gestational exposure to haloperidol or penfluridol and a control group counseled for nonteratogen exposure. This multicenter, prospective, controlled study was conducted within the European Network of Teratology Information Services (ENTIS) and included women who contacted 1 of 4 teratology information services for counseling between January 1989 and December 2001. We followed up on the outcomes of 215 pregnancies exposed to haloperidol (N = 188) or penfluridol (N = 27)-78.2% (of 206) were in the first trimester-and compared to outcomes of 631 ENTIS controls. The rate of congenital anomalies did not differ between the haloperidol/penfluridol-exposed group and the control group (6/179 = 3.4% vs. 22/581 = 3.8%, p = .787). No difference was found by limiting the analysis to those exposed to butyrophenones during the first trimester. There were 2 cases of limb defects in the butyrophenone-exposed group (1 after haloperidol and 1 after penfluridol exposure) and none in the controls. A higher rate of elective terminations of pregnancy (8.8% vs. 3.8%, p = .004), a higher rate of preterm birth (13.9% vs. 6.9%, p = .006), a lower median birth weight (3155 g vs. 3370 g, p < .001), and a lower median birth weight of full-term infants (3250 g vs. 3415 g, p = .004) were found in the butyrophenone-exposed group compared to the controls. This study suggests that haloperidol and penfluridol do not represent a major teratogenic risk. Since a possible association between butyrophenone exposure and limb defects cannot be ruled out with this sample size, a level II ultrasound with emphasis on the limbs should be considered in pregnancies with first trimester exposure.

Maternal exposure to first‐trimester sunshine is associated with increased birth weight in human infants

Two alternative hypotheses have been generated to account for seasonal variation in the birth weight of human infants born in industrialized countries. First, it has been hypothesized that low ambient temperature during the second trimester of gestation decreases birth weight. Second, it has been hypothesized that exposure to bright sunshine during the first trimester increases birth weight. We tested these two hypotheses to determine which, if either, accounted for seasonal variation in birth weight of full-term infants. Birth weight data, collected over a 5-year period, were analyzed as a function of peak and trough sunshine and ambient temperature. Although there was no effect of ambient temperature during any trimester on birth weight, infants whose mothers were exposed to peak sunshine during their first trimester were born significantly heavier than infants whose mothers experienced trough levels of sunshine during the same trimester. Furthermore, infants whose mothers were exposed to trough levels of sunshine during their second and third trimesters were born significantly heavier than infants whose mothers were exposed to peak levels of sunshine during the same trimesters. We hypothesize that high levels of sunshine during early gestation may increase the level of insulin-like growth factor (IGF)-1, facilitating prenatal growth.

Birthweight of full-term infants is associated with cord blood CD34+ cell concentration

CD34+ cell counts are used to define the haematopoietic stem cell potential of a given cord blood transplant. The aim was to test the hypothesis that high concentration of cord blood haematopoietic progenitor and stem cells could be a reflection of intrauterine growth, of which birthweight is an indicator. Simple and multiple regression analyses were applied to test cord blood bank data on 1368 infants for associations of selected obstetric factors and cellular contents of cord blood. When groups were formed based on the extreme values (5th versus 95th percentiles) of a given variable, e.g. birthweight, the term infants having the highest birthweights were found to have statistically significantly higher median cord blood CD34+ cell concentrations. Also, infants in the top 50th percentile of relative birthweight had higher median CD34+ cell concentration than infants in the low 50th percentile. In multiple regression analysis, the correlation between birthweight and CD34+ cell concentration was statistically clearly significant. Notably, while an expected correlation between gestational age and nucleated cell concentration was found, there was no association between infant gestational age and CD34+ cell concentration. Haematopoietic progenitor and stem cells may reflect intrauterine growth and have a more central role in foetal development than has been reported earlier.

Early postnatal growth in preterm infants and cord blood leptin.

Although circulating leptin and insulin concentration is linked to intrauterine growth, fetal development and birth weight in full-term infants, there has been no enquiry into the influence of cord blood insulin and leptin for catch-up growth in preterm infants. The study evaluated the association of cord blood leptin with growth and weight gain of 96 premature babies during 6 months (corrected age). The temporal changes of anthropometric indexes over this period were calculated by repeated random regression (PROC MIXED) using SAS. Cord blood leptin was negatively associated with the rate of change in BMI (p=0.01) and length (p<0.001), from birth until 64 postnatal weeks. Insulin was positively associated with the change rate in BMI (p=0.03); however, this disappeared when adjusted for birth weight. For the first time, the association between lower leptin levels with greater catch up growth is shown for both BMI and length among preterm children. In conclusion, leptin levels at birth, but not insulin levels, predict growth rates.

The influence of khat-chewing on birth-weight in full-term infants

The leaves of the shrub Catha edulis (khat) are widely chewed as part of social life in several countries around the Red Sea and in East Africa. The leaves possess stimulant properties and are also used by pregnant women. The effect of khat on birth-weight has been studied, It was found that healthy full-term, singletons, born after uneventful pregnancies and deliveries, had a significantly lower average birth-weight when the mothers were khat-chewers, either habitually or occasionally ( P<0.001). Khat- chewing appears to be one of several maternal practices adverse to the fetus.

Intracranial Pressure

Intracranial pressure (ICP) was measured sequentially using a pressure-activated fiberoptic device that is placed over the anterior fontanel in 120 full-term and 53 preterm infants during the first week after birth. Mean birth weight in full-term infants was 3,527 g (range, 2,720 to 4,620 g) and in preterm infants was 1,695 g (range 1,130 to 2,440 g). Mean ICP was 12.6, 12.1, and 11.4 cm H2O on days 1,2, and 3 in full-term infants, and was 10.2, 17.0, 11.0, 8.9, 7.3 cm H20 on days 1, 2, 3, 5, 7 in preterm infants. The values in preterm infants did not seem to be related to differences in Apgar scores, but higher values were seen in infants treated with continuous positive airway pressure administered by nasal prongs (before the method of fixation was changed). More stable values have been seen recently in preterm infants, which may reflect changes in care (eg, less hypoxemia).

Prenatal Exposure to Prednisone in Humans and Animals Retards Intrauterine Growth

Reinisch, June Machover; Simon, Neal G.; Karow, William G.; Gandelman, Ronad Author Information

Prenatal exposure to prednisone in humans and animals retards intrauterine growth.

Prednisone treatment for infertility and subsequent pregnancy maintenance in humans resulted in a significant decrease in the birth weight of full-term infants and a marked increase in the percentage of newborn infants weighing 2500 grams or less, that is, "light for dates" in comparison to control offspring. A parallel experiment with mice indicated that the reduction of birth weight was caused by exposure to corticosteroids rather than to maternal disease or malfunction.

EPIDEMIOLOGY OF THE HYPOPLASTIC LEFT HEART SYNDROME IN ONTARIO, 1971–73

This study had as its purposes the description of hypoplastic left heart syndrome (HLH) in Ontario and the testing of a specific hypothesis about geographic clustering of the defect in the vicinity of Toronto. A series of 52 cases of HLH born in Ontario during 1971 to 1973 was studied, and its characteristics contrasted to those of all other infants born during those years. Cases were ascertained from death certificate information made available by the Registrar-General of Ontario. There were no false-negatives among infants known to us to have died from any congenital heart defect. False-positives among the death certificates were distributed as was the pattern of infant deaths. Autopsy rates for infant deaths in different regions of the Province are comparable. The cases clustered beyond chance expectation in the populous southern part of Ontario (p < .02), but also seem to be associated with some characteriatic(s) of the more ‘rural’ parts of the Province. Birthweight in full-term infants who had HLH tended to be depressed from that of normal full-term infants (p < .02) when the overall distribution is considered. This series contradicted previous suggestions in that we could not demonstrate either elevated parental age or any significant seasonal pattern in dates of conception or of birth.