Tuesday, June 24, 2008

Biological risks of teenage pregnancies

There are good reasons why people have pushed back having babies until later in life. Success in modern society takes a great deal more education than in previous years meaning teen pregnancy can make it difficult to avoid poverty later in life. However if you listen to people talk they act as if it is also a serious biological problem, as if teenagers are not yet mature enough to make babies. So, I decided to see what I could find in the way of statistics. These were actually fairly difficult for me to find, but ill show what I have.


This illustrates a theme in just about all of the numbers I saw. Teenage mothers are less biologically capable than mothers in their twenties. However in just about every biological measure they do better than mothers over 35, and often over 30.

I decided to take a look at pages trying to talk teens out of pregnancy, than chase data a little. One site claimed that teenage mothers were more likely to have children underweight than mothers 20-24. That struck me as really funny for some reason. It was clearly fudging the data to fit what they wanted, so I chased down some numbers for the percent of babies that were underweight.
Under 15: 11.6% 11.6%
15 - 19 : 7.6% 7.6%
20 - 24 : 6.2% 6.2%
25 - 29 : 5.9% 5.9%
30 - 34 : 6.4% 6.4%
35 - 39 : 7.9% 7.9%
40 - 44 : 9.9% 9.9%
45 and Above: 23.6% 23.6%

Sure enough, the statistic they claimed is true, but it ignores the big picture. Since most teenage mothers are 18 or 19 it really misses the point even more because past the age of 15 they have less problems than mothers over 35. The under 15 category is more likely to have unhealthy babies than the 35+ mothers, but that is not terribly surprising as a twelve year old is fairly obviously not biologically mature, and a fairly large proportion of mothers in that category will be that young.

Now, not having it broken down exactly it is hard to say exactly what age the risk drops to being equal, but because many birth defects like Down Syndrome become more common as mothers age I feel reasonably certain in making the claim that a 15 year old, and a 35 year old are about the same in terms of biological readiness to make babies.

Teenage pregnancy statistics are thrown way off because teenage mothers are poorer than the general population, and poorer people have worse medical care. When you standardize for that the case for teenage mothers being as biologically capable gets a whole lot stronger. The only study I am aware of to do this, looking at teenage pregnancies, and pregnancies to older women holding constant socioeconomic status, found that:

"If you compare Harlem teen moms to Harlem older moms, you find that the kids of the teen moms are actually less likely to die," she said. The reasons include the fact that, unlike older women, poor teenagers are generally not juggling jobs and have older relatives to help.

It can make sense for poor women to have children when they are quite young, Geronimus concludes, and any effort to change that ought to treat it as an economic problem, not a health education problem." Source

Now to push a little harder, and make the case that biologically young mothers are better than old(although I think all the data I saw was pretty identical in its view that 20-25 is about the optimal biological time to make babies).

There has been a lot of research into what exactly allows people to live longer, in particular I am referring to scientists looking at people who have lived to be 100 to see if there are biological differences. One of the shocking findings they had was that babies born to mothers under the age of 25 were more than twice as likely to make it to 100 years of age. Now, I wouldn't bet my life on this study just because I have an inherent distrust of epidemiological studies, but the odds are in favor of this turning out to be correct. Notice how they did not put a lower end on that age range? At the time these babies were being born teenage pregnancy rates were far higher than today so you can bet a large percentage of those mothers were under 20.

The socioeconomic case on the other hand is quite good. We rightly should be telling high school students that they should wait to have babies until they are economically more stable. It just bugs me to see people make it sound like the evidence here is a whole lot stronger than it is. Biologically teenagers are well constructed to make babies, and the reasons they shouldn't are entirely based on the particulars of our society. If marriages of 15 year olds were stable, and you only needed an 8th grade education(much like the United States just a century back) there would be no moral problem with the pregnancy pact story that for some odd reason is all over the media.

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