Teenage childbearing : pregnancy outcomes and long-term consequences for the mothers

Abstract

The purposes of the thesis were to study effects of low maternal age on adverse pregnancy outcomes, predictors of teenage childbearing, and long-term effects of teenage motherhood on the women's social situation later in life and risk of premature death.

The effects of low maternal age at first birth on risks of adverse pregnancy outcomes, primarily preterm birth and infant mortality, were studied in three population-based cohort studies. We used the Swedish Medical Birth Register, the 1990 Population Census, and the population-based Education Register. The poorer pregnancy outcomes among teenagers aged 18-19 years are mainly an effect of a less favourable socio-economic situation. Infants of younger teenage mothers face an overall increased risk of preterm birth, neonatal and postneonatal mortality that is independent of socio-economic situation. The increased risk of neonatal mortality is entirely an effect of the increased risk of preterm birth. To study whether the increase in risk of poor pregnancy outcomes is due to low age per se, we also studied pregnancy outcomes at second birth in relation to age at first birth. When teenage childbearers had their second birth in adulthood, the risk of preterm birth has declined more than the corresponding risk decline among mother who also had their first birth in adulthood. Our results support the hypothesis that young age is a risk factor for poor pregnancy outcomes, independent of socio-economic conditions.

To study familial and environmental effect as predictors of teenage childbearing, we linked the Swedish Twin Register to the Medical Birth Register. We used quantitative genetic analyses to evaluate the impact of genetic and environmental factors on the risk of teenage childbearing. We estimated the effect of life style factors, socio-economic situation, and personality traits on the likelihood of teenage childbearing, and if these factors could explain possible familial effects. Both familial and other environmental factors are important as predictors of teenage childbearing. We found significant effects of smoking habits, housing conditions, and educational level on the risk of teenage childbearing. However, the familial effect on teenage childbearing was not mediated by these factors.

In two studies we analysed long-term socio-economic conditions and premature mortality of teenage mothers. We linked the following population-based registers: the Population Register, several Censuses, the Education Register, the Cause of Death Register, and a register of dependence on social welfare and disability pensions. Teenage childbearers face a considerably increased risk of a less favourable situation later in life. They are more likely to be not gainfully employed, to have an unskilled occupation, to be single mothers, to have four or five infants, to be dependent on social welfare and receive disability pensions. Teenage mothers also face an increase in risk of premature death due to in particular cervical cancer, ischaemic heart disease, suicide and inflicted violence. The increased risk of as well a less favourable social situation as premature mortality was independent of background socioeconomic status.