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Biomedical subjects

H Oja

Publications and source records attributed to H Oja.

4 recordsLinked to original sources
PubMed1992

Perinatal outcome of pregnancies complicated by vaginal bleeding.

OBJECTIVE: To examine the effect of first and/or second trimester vaginal bleeding on pregnancy outcome. DESIGN: A prospective one-year birth cohort. SETTING: Two northernmost administrative districts of Finland. PATIENTS: 8718 singleton pregnancies, of whom 807 (9.3%) reported bleeding during the first (601) and/or second trimester (206); light bleeding in 595 cases and heavy bleeding in 212. The remaining 7911 women served as a reference group. MAIN OUTCOME MEASURES: Low birth weight rate (LBW), preterm birth rate, congenital malformations and perinatal mortality rate. RESULTS: Bleeding was most frequent in women of more advanced age (> or = 35 years old), with previous miscarriages, with infertility problems or using an IUCD prior to the pregnancy. Parity, smoking and social status were not associated with bleeding. Caesarean section rate and placental complications during the third trimester and at delivery were more common among the bleeders than in the reference group. The LBW rate was three-fold among the bleeders and the preterm birth rate two-fold. The risk (OR) of a LBW infant among second trimester bleeders was 4.1 (95% CI 2.6-6.4), that of preterm birth 2.9 (95% CI 1.9-4.6), and that of congenital malformations 2.9 (95% CI 1.7-4.7). No association existed between bleeding and perinatal mortality. CONCLUSIONS: Bleeding during the second trimester indicates a poor pregnancy outcome and an increased risk of LBW, and preterm birth and/or congenital malformation.

Adult↗
PubMed1991

Fitting mixture models to birth weight data: a case study.

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.

Algorithms↗
PubMed1990

Perinatal risk for infants of unmarried mothers over a period of 20 years.

The perinatal events of the infants of 444 unmarried mothers, 3.7% of the total Northern Finland birth cohort from 1966, were compared with those of infants of 11,525 married mothers (95.5%), and a similar comparison was made between 395 (4.2%) unmarried mothers and 7516 (80.3%) married mothers in a second Northern Finland birth cohort in 1985-86. 1336 mothers, 14.3% of the mothers in this later cohort, were cohabiting. Divorced and widowed mothers were excluded from both cohorts. The infants of the unmarried mothers had a significantly lower mean birth weight, were more likely to be small for their gestational age (SGA), of low birth weight (LBW) (below 2500 g) and had a higher incidence of pre-term births than those of the married mothers in both cohorts. Perinatal mortality was significantly higher among the unmarried mothers only in the former cohort. These differences in perinatal events diminished markedly after adjustment for maternal age, parity, height, years of schooling and smoking habits, but did not totally disappear. The difference in the incidence of pre-term births diminished, but remained significant in both cohorts. The difference in mean birth weight, in the incidence of LBW infants and in perinatal mortality remained significantly less favourable to the unmarried mothers only in the 1966 cohort. It seems that the gap between the married and unmarried mothers had diminished. The incidence of SGA infants did not differ significantly between the married and unmarried mothers in either cohort after adjustment for the background variables. The cohabiting mothers formed an intermediate group between the married and single unmarried mothers in respect of perinatal events, but were close to the married mothers. In raw figures, the mean birth weight in this group was significantly lower and the incidence of SGA infants higher than among the married mothers, but these differences also disappeared after adjustment of the background variables.

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