A list of the reproductive ills that afflict our species might start with placental abruption, hyperemesis gravidarum, gestational diabetes, cholestasis and miscarriage, and carry on from there. In all, about 15 per cent of women suffer life-threatening complications during each pregnancy. Without medical assistance, more than 40 per cent of hunter-gatherer women never reach menopause. Even with the help of modern medicine, pregnancy still kills about 800 women every day worldwide.
How does an embryo convince its mother that it is healthy? By honestly displaying its vigour and lust for life, which is to say, by striving with all its strength to implant. And how does the mother test the embryo? By making the embryo’s task incredibly difficult. Just as the placenta has evolved to be aggressive and invasive, the endometrium has evolved to be tough and hostile. For humans, the result is that half of all human pregnancies fail, most at the implantation stage, so early that the mother may not even realise she was pregnant.Suzanne Sadedin has a PhD in Zoology from Monash University, and has since held research positions at Monash University, the University of Tennessee, Harvard University and KU Leuven.