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Being stressed is not good for a pregnant mother, but how the baby reacts to the stress depends partly on its gender. Research led by Vicki Clifton from the University of Adelaide is finding out how stress changes the way babies develop.

When you’re pregnant, I imagine anything can stress you out. Were I up the duff (which I am not), I would most certainly stress about demon possessions… I can’t help but think of Omen and the Ring.

But it’s not just the mind. Asthma attacks, smoking and pre-eclampsia can put pregnant bodies under stress. The mother can communicate that stress to the baby while it’s still in the womb. Cortisol, a molecule involved in stress, causes changes in the placenta – but only if the baby is female.

A female baby will slow her growth when her mother is stressed. How thoughtful! By growing slowly she takes less energy and nutrients from her mother, which the mother might need to recover.

In contrast, a male baby does not change his growth with a stressed mother. He just keeps growing as fast as he can.

At first glance, it seems like a smart move for the male baby. Mother is stressed, something might be wrong, better grow as fast as you can and get the hell outta there. Unfortunately it’s not a good option. If there’s a second stressful event, the male baby is at risk of pre-term delivery or dying in the uterus. A female baby who has curbed her growth has a better chance of surviving.

The Darwin obsessed among you might wonder what evolutionary advantage is made by females reacting better to stress. If you have any ideas let me know, because I’m stumped.