Blogosaurus Vex

February 3rd, 2009

Remember when we were talking about maternal behaviour affecting the fetus?  And we used smoking as an example?  I just read this neat little article that talks about that very thing.  While the conclusions are unsurprising (smoking while pregnant results in a baby about a pound lighter than non-smokers’ babies, statistically significant and separate from whether the fetus is related to the womb carryer or not), other conclusions were unexpected (antisocial behaviour is increased when the fetus is related to the carryer and she smokes).  But the real reason I’m posting this link and excerpt is because it illustrates some of the complexities in determining whether there is a simple one-to-one cause and effect relationship between maternal behaviour and outcome.  That’s the piece in this quotation:

Our health isn’t just affected by the things we do after we’re born – the conditions we face inside our mother’s womb can have a lasting impact on our wellbeing, much later in life. This message comes from a growing number of studies that compare a mother’s behaviour during pregnancy to the subsequent health of her child.

But all of these studies have a problem. Mothers also pass on half of their genes to their children, and it’s very difficult to say which aspects of the child’s health are affected by conditions in the womb, and which are influenced by mum’s genetic legacy.

Take the case of smoking. Doing it while pregnant is bad news for the foetus, and studies have suggested that children whose mothers smoke during pregnancy are more likely to be born prematurely, be born lighter, have poorer lung function, and be more likely to die suddenly before their first birthday. More controversially, they may even show higher levels of behavioural problems including autistic disorders and antisocial tendencies.

Biologically, these results make sense, but many of these risks can be inherited too. For example, genetic factors can strongly influence both a person’s susceptibility to nicotine addiction and their propensity for violent behaviour. A mother’s genes could also affect the birth weight of her child.

To untangle these influences, the ideal experiment would involve randomly implanting foetuses either in the wombs of their own mothers, or those of unrelated women. That’s possible in animals but deliberately doing so in humans would be both unethical and impractical. Nonetheless, Frances Rice from Cardiff University realised that this experiment was actually well underway.

Read the rest here.

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