Mortality, major neurological handicaps--including mental retardation, cerebral palsy and epilepsy--educational subnormality and height at 14 years of age were studied by birth weight percentiles in a birth cohort of 12 000 children from northern Finland. Infant mortality was significantly higher below the mean -2 SD, 10th and 25th percentiles, than in the median class, from 25th to 75th percentiles, but mortality from one to 14 years only in the lowest weight class. Educational subnormality, including mental retardation +/- some other handicap, was highly significantly more frequent in all the percentile classes lower than the median class but showed no significant tendency to be less frequent in the percentiles over the median. It was also highly significantly more frequent among the preterm than the term infant. The number of children with a major neurological handicap but normal school performance did not vary significantly by birth weight percentiles or by gestational age. Height at 14 years increased significantly by birth weight percentiles. The height of the boys with birth weight mean - and +2 SD was nevertheless within the 25th-75th percentiles for height at 14 years in general, while the height of the girls came close to these percentile limits. The preterm infants were significantly shorter than the term infants at 14 years.
This study evaluates the impact of regional differences in access to intensive neonatal care on neonatal survival in geographically defined populations of 4,692 low birthweight births in Norway 1979-81. For infants weighting 1,250 to 2,499 g our results are consistent with the existence of a dose-response association between neonatal survival and the level of immediate access to intensive neonatal care. Although not statistically significant, there was a clear gradient in the risk of mortality within 24 hours. A similar pattern of survival could not be consistently demonstrated for infants weighing less than 1,250 g.
The association of perinatal events, childhood epilepsy, and central nervous system trauma with juvenile delinquency was studied prospectively in a geographically defined population of 5966 males in northern Finland. Those who had obtained a criminal record up to the age of 22 years, totalling 355, or 6.0%, were defined as delinquents. The incidence of delinquency was not increased in males with a birth weight less than 2500 g or greater than 4000 g, preterm births
In order to estimate the association between intrauterine growth and childhood survival, data on birth weight and gestational age from the Norwegian Birth Registry, for all children who survived the first year of life and who were born during the period 1967-1989 were linked to the National Cause of Death Registry for the period 1968-1991. Deaths were categorized into five cause of death groups: malformations, cancer, infections, accidents, and other causes. The adjusted relative risk of death from all causes at ages 1-5 years was 2.18 (95% confidence interval (CI) 1.85-2.56) for children with birth weight or = 2,500 g. For ages 6-10 years, the corresponding adjusted relative risk (95% CI) was 1.83 (1.35-2.48), and for ages 11-15 years, it was 1.35 (0.91-1.99). Death from infections, accidents, and other causes showed a reversed J-shaped association with birth weight, while malformations showed a log-linear decrease in mortality with increasing birth weight. For cancer deaths, low birth weight showed an opposite association. The association between birth weight and childhood mortality is complex, and cause-specific analyses are necessary to understand the connection between intrauterine influences and later mortality.
OBJECTIVE: To describe birthweight by gestational age in Norway for the period 1967-1998, evaluate secular trends and provide new standards for small for gestational age for 16 to 44 weeks of gestation. SUBJECTS AND METHODS: The analyses were based on more than 1.8 million singleton births, covering all births in Norway for a 32 year period. Percentiles for birthweight by gestational age were estimated using smoothed means and standard deviations. In the preterm weeks, means and standard deviations were carefully screened for birthweight-gestational age consistency, adapting a method of Wilcox and Russell. Differences in birthweight by gestational age for stillbirths and livebirths in extremely preterm weeks (16-28) are presented, and the effects of cesarean section are evaluated. We observed a clear increase in birthweight by gestational age for all term weeks, but a decrease for most of the preterm weeks over the same period. This decrease was related to the increase in deliveries by cesarean section. CONCLUSIONS: Percentiles for birthweight by gestational age are presented for clinical use, based on a current period 1987-98, covering 20-44 completed gestational weeks. In the final standards we excluded stillbirths, infants born with malformations and cesarean sections. Birthweights in the Scandinavian populations are high and standards from other populations may not be representative, especially for the term weeks. Also, the secular changes demonstrated in this study indicate that old birthweight by gestational age standards need revision, especially due to changes in obstetrical routines influencing preterm data.
At low birth weight the variance of last menstrual period based gestational age is wide and the distribution is positively skewed toward higher values. In this study the variance of gestational age decreases rapidly as birth weight increases, skewness decreases and kurtosis increases in approaching the mean of the birth weight distribution. Some of the wider variance and positive skewness of gestational age at low birth weight appears to reflect heterogeneity of intrauterine growth, in which infants with high values of gestational age are growth retarded. We show by partitioning each birth weight group into two groups of infants with different gestational age distributions, that at low birth weight, infants with low gestational ages have higher neonatal mortality rates but lower fetal mortality rates than infants with a higher gestational age for birth weight. The differences in mortality described between small infants at different gestational ages suggest that infants with a high LMP-based gestational age have experienced a slower rate of intrauterine growth. Some authors interpret the distributional characteristics as indications of systematic error in last menstrual period based assessment of gestational age. It appears from this study that the extent of systematic error in the estimation of LMP based gestational age may have been overstated in the past.
BACKGROUND AND METHOD: Small-for-gestational-age (SGA) infants represent a heterogeneous group of normal and growth-retarded children. To assess the familial aggregation of reduced fetal growth, birth weights in both maternal and paternal relatives of 1246 index children in the Scandinavian SGA Study were compared across groups defined by the SGA outcome of the index child as well as that of earlier siblings. RESULTS: Mean maternal birth weight +/- SEM was 3127 +/- 54 g for mothers who had experienced two SGA births as opposed to 3424 +/- 22 for mothers with no SGA births. Mean paternal birth weight was 3497 +/- 88 g and 3665 +/- 24 in the same two groups. The odds ratio (with 95% confidence interval) for having a mother with birth weight below the 10th percentile was 1.74 (0.85-3.58) for the group where two SGA births had occurred compared to no SGA births and it was 2.49 (1.22-5.07) for having a father with birth weight below the 10th percentile. There was no correlation between maternal and paternal birth weights. CONCLUSIONS: The association also to paternal birth weight suggests the presence of genetic or common environmental factors in explaining the tendency to have SGA children. Although taking parental birth weights into consideration will aid in diagnosing growth-retardation in a SGA child, SGA remains a heterogeneous group where familial and non-familial cases will be difficult to separate.
The acceptability of pregnancies was studied in two birth cohorts in Northern Finland which represent 96% of all births in the region in 1966 (12,068 births) and 99% (9362 births) in 1985-1986. The numbers of women of fertile age in the area during these years were 148,000 and 158,000, so that fertility may be said to have fallen from 81 to 59 per 1000. The pregnancy was wanted in 63.0% of cases and unwanted in 12.2% in 1966, the rest being classified as accepted later. The corresponding figures in 1985-1986 were 91.8% and 1.0%. The latter figures changed very little when maternal age, parity and social class were standardized to the 1966 levels. Acceptability was connected with age, in that the age groups in which childbearing was most frequent, 20-25 years in 1966 and 26-30 years in 1985-1986, had the highest incidence of desired pregnancies. In spite of the fact that there were 1.4 times as many births per woman aged 15-49 years in the former cohort, more wanted children were born to the age group 25-34 years in the latter cohort. The percentage of wanted pregnancies also varied with the woman's parity, social class and marital status. The children in the 1966 cohort were followed until the age of 14 and the incidences of cerebral palsy (CP) and mental retardation (IQ less than 71) were 3.2 times higher among the unwanted children than among the wanted ones.(ABSTRACT TRUNCATED AT 250 WORDS)