Teenage pregnancy: an evolutionary explanation

Travis DixonBiological Psychology

In this post we use evolution to explain the link between childhood ACEs and teenage pregnancy.

Adverse childhood experiences (ACEs) have been linked with increased risks of developing a number of issues, including health problems (cancer, heart disease), psychological problems (addiction, depression) and sexual health issues (STDs, high-risk sexual behaviour and unwanted pregnancies). Studies have shown that teenage pregnancy is correlated with ACEs and there might be an evolutionary explanation for this link.¹

ACEs are associated with a number of negative outcomes throughout our lives.

Most teenage pregnancies are unplanned and have many consequences, especially for the mother. This includes negatively impacting education and employment opportunities for the future. So why do they happen? Like most psychological and societal issues, we might be able to trace them to ACEs.

There are a number of possible ACEs that someone might experience in their lifetime. In fact, most people have experienced at least one. Examples of ACEs include divorce, experience physical, sexual or emotion abuse, neglect, living in poverty or living with someone with a psychological disorder, alcohol or drug addiction. Large-scale correlational studies have shown that psychological and health problems increase with the more ACEs experienced.

The same can be said for teenage pregnancy – more ACEs results in higher chances of teenage pregnancies.

Evolutionary Explanation of Teenage Pregnancy

If you live in a dangerous environment, it makes evolutionary sense to procreate sooner rather than later. However, this subconscious survival instinct makes evolutionary sense for our early ancestors and definitely does not apply for modern society.

Explaining behaviour through evolution means showing how the behaviour helps an individual to survive, procreate and/or pass on their genes. In this case, we’ll be looking at the latter – how teenage pregnancy can help an individual to pass on their genes. Since teenage pregnancy is linked with so many negative outcomes in adult life, it seems strange that this same behaviour can be linked with survival and genetics.

But it’s actually quite logical. If you are experiencing lots of ACEs (more than 7), it means your environment is filled with danger. More ACEs equals more danger. So in terms of passing on your genetic material (which is the biological purpose of life) your best bet is to do this sooner, rather than later. It’s important to remember that these are not conscious, well-thought out decisions. This behaviour is happening at a subconscious level.

Where’s the evidence for this link?

It’s important to remember that these are not conscious, well-thought out decisions. This behaviour is happening at a subconscious level. Remember also that evolutionary explanations make sense when we think about our early ancestors living thousands of years ago. Unwanted pregnancies in dangerous environments is a disastrous idea in modern society.

If you are concerned about your own experiences with ACEs, please seek help by contacting your school’s guidance counsellor, a local helpline (google “helpline in my area”), your nearest police department or even hospital.

Associations between ACEs and Teen Pregnancy (Hillis et al. 2004)

Hillis et al. (2004) conducted a study with the aim of seeing if ACEs were associated with teenage pregnancy. They also wanted to see if there was a link between ACEs and teenage pregnancy with long-term psychological consequences.


  • Data from over 9,000 women was used in this study.
  • It was a retrospective study, meaning the data had already been gathered in the 1990s as part of regular health evaluations.
  • ACEs were measured using self-report questionnaires that measured childhood abuse or household dysfunction.
  • Data on pregnancy was measured by asking direct questions in the ACE questionnaire, e.g. “How old were you the first time you became pregnant?”
  • They defined teenage pregnancy as between ages 11-19.
  • The researchers collate the data to see if there was a link between ACEs and teenage pregnancy.


Data was not gathered at time of pregnancy, but retrospectively (participants were average age of 56 years old when they filled out the questionnaires).

  • There was an increased rate of teenage pregnancy that rose with the increase in ACEs.
    • 16% of women with zero ACEs were first pregnant as a teenager.
    • 1 ACEs = 21%
    • 2 ACEs = 26%
    • 3 ACEs = 29%
    • 4 ACEs = 32%
    • 5 ACEs = 40%
    • 6 ACEs = 43%
    • 7 – 8 ACEs = 53%
  • The results also showed that ACEs were positive associated with an increase risk of other negative outcomes in adult life, like job problems, financial problems, high stress, family problems and uncontrollable anger). That is to say, more ACEs increased the rates of these problems.


  • Experiencing ACEs as a child might increase the risk of teenage pregnancy and other negative outcomes in adult life.


  • Understanding the negative consequences of ACEs has become a massive focus for governmental organizations, especially those focusing on the welfare of the most vulnerable: children, minorities and the poor. Studies like Hillis et al. could provide evidence to help justify the development and funding of programmes designed to reduce teh rate of ACEs in a particular society.

Critical Thinking Considerations

  • This study is only correlational, which means we can’t deduce a causal relationship. The logical conclusion is that ACEs (Variable A) lead to an increase in child pregnancies (Variable B). But is there a way we could explain this by showing how B might affect A?
  • This study used data gathered in the 1990s. Moreover, the women were an average age of 56 when they filled out the data asking about their childhood experiences. Can you see reasons why we might question the validity of this data?
  • What ethical considerations can see you that might be relevant to this study?


Hillis SD1, Anda RF, Dube SR, Felitti VJ, Marchbanks PA, Marks JS. The association between adverse childhood experiences and adolescent pregnancy, long-term psychosocial consequences, and fetal death. Pediatrics. 2004 Feb;113(2):320-7.
¹I was first made aware of this link and the potential explanation while listening to a Dr Drew podcast.