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.
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
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)
This multilevel study of spatial variability in, and determinants of, birthweight was conducted using individual and ecological data in a geographically defined prospective birth cohort for 1986 in northern Finland. The study area comprises three large areas defined by latitude: Northern Lapland (NL), Southern Lapland (SL) and Oulu province (OP), comprising 74 localities with a total study population of 9216 singleton births. The mean birthweight was 3482 g for NL, 3537 g for SL and 3587 g for OP (NL vs. OP and SL vs. OP: P
Participation in further education after compulsory schooling was examined for 377 LBW (low birth weight, or = 2500 g) children and completion of this further education among the same population in a 1-year birth cohort for Northern Finland in 1966. There was no difference in enrollment for further education, the percentage for non-enrollment was 8.5% for LBW and 7.0% for NBW children, and the healthy LBW children even enrolled more often than the healthy NBW children. Enrollment among the disabled LBW children, however, was significantly poorer than among the disabled NBW children, 57.1% and 36.8%, respectively failing to enroll. The disabled LBW girls in particular enrolled poorly, 76.9% of them failing to do so. Completing further studies up to the age of 24 was rarer among the LBW children than among the NBW children, 17.6% of them failing to graduate compared to 13.8% of the NBW children. If the disabled children were excluded, however, the healthy LBW children succeeded as well as the healthy NBW children. The LBW girls, especially the disabled ones, graduated the least often. When excluding the disabled children and controlling confounding variables by stratification, low birth weight did not affect non-enrollment or non-graduation. Altogether, the success of the LBW children in their post compulsory education was satisfactory except for the disabled LBW children, especially the girls.
Birth weights by gestational age are compared in two birth cohorts from Northern Finland, the first from 1966 and the second from 1985-1986. A curious fact in the data is that mean birth weight before the 39th week was lower in the latter series although the mean birth weight for the total series was higher. Similar findings have been reported in other series. A mixture model with the nonparametric regression function is proposed for studying the hypothesis that the difference was caused by more frequent gross errors in gestational assessment in the earlier cohort. The probability of an error in gestational assessment then greatly depends on the observed gestational age, which makes the mixture model nonstandard. Maximum likelihood solutions to the parameters in the proposed model were computed employing the general expectation-maximization (EM) algorithm. A technique for studying the effect of errors on the intrauterine weight gain curve is proposed and applied to our two birth cohorts. The risk of underestimation of gestational age seems to be larger in the previous series and the differences between the growth curves almost totally vanish when "corrected" by means of the mixture model.