Numerous studies have been conducted on the impacting factors for pregnancy outcomes in young women, yet so far, no study has established which of these factors are the most important and the impact of depression on pregnancy outcomes is particularly unclear.

Researchers from Norway's Institute of Public Health and the Centre for Adolescent Health, Murdoch Children's Research Institute together with Australian researchers from the Royal Children's Hospital in Melbourne have now discovered that the most significant risks for becoming pregnant and abortions in young adulthood are adolescent antisocial and drug use behavior.

The researchers examined the link between depressive symptoms in 14 to 18 year old adolescent girls and their pregnancy outcomes aged between 21 to 24 years as young adults.

The research included data from 988 young Australian women who participated in The Victorian Adolescent Health Cohort Study, a longitudinal study who were followed from age 14 in 1992 until today.

The team defined pregnancy outcomes as becoming pregnant, as well as completing and/or terminating a pregnancy. The researchers checked participants for depressive symptoms six times during adolescence. Pregnancy outcomes were evaluated twice during young adulthood.

The participants were also surveyed in terms of their degree of antisocial behavior, including vandalism, car damage, graffiti, fighting, theft and expulsion from school and drug use, including smoking, cannabis and alcohol during their teenage years in order to assess other possible influences on pregnancy outcomes. The researchers also took into consideration the women's socio-economic data, including parental education and marital status and discovered an elevated risk of pregnancy in those who reported high depressive symptoms on several occasions during adolescence in comparison with those who reported no such symptoms.

However, the researchers observed that this link was eliminated when they considered the participants' antisocial and drug use behavior, as well as socio-economic variables. They noted, in particular, that adolescent antisocial and drug use behavior had the strongest link to becoming pregnant and having an abortion in young adulthood.

Leading author, Wendy Nilsen, said:

"The findings support previous research that suggests a relationship between depression and pregnancy outcomes, but indicate that this relationship either is confounded with or can be explained by antisocial and drug use behavior."

The research therefore demonstrates the importance of accounting for other possible causal factors in addition to the factor of initial interest.

Nilsen explains:

" The findings are useful because they underscore the relationship between antisocial and drug use behavior and pregnancy outcomes in young women. More studies are nevertheless needed before one can say anything clear about the causal relations, but the results suggest that selectively helping young people with a history of antisocial and drug use behavior may improve the future sexual and reproductive health outcomes in this group."

The findings are also significant in relation to earlier research that was mainly based on pregnancy outcomes in teenagers, and not in young adults. Whilst in 1971, the average age of first-time mothers in most Western countries was 25 years, nowadays the term "early pregnancy" also applies to pregnancy in young adulthood with first-time mothers average age being 31 years.

The study outcome indicates that some of the same factors, such as antisocial and drug use behavior, which are linked to pregnancy outcomes in teenagers also relate to pregnancy outcomes in young adult women. The researchers suggest that the difference in the average age of first-time mothers validates further studies into pregnancy, lifestyle and mental health, and Nilsen concludes: "Further research could look at whether getting pregnant in young adulthood affects some life role transitions, such as establishing a career and/or family."

Written by Petra Rattue