William Richard Rice, an evolutionary geneticist at the University of California, looked at past studies and databases to compare miscarriage frequency to the number of babies born. He found that the majority of eggs fertilised by sperm, never actually grow into children.
The reason? Deadly genetic abnormalities which stop eggs from developing in utero.
“It’s not an abnormality. It’s the norm,” he told New Scientist, adding that this was “unambiguously” the “most common outcome of conception across a woman’s lifetime.”
Previous research has found that somewhere between 10 and 20 per cent (or as many as 1 in 4) known pregnancies end in miscarriage (a phenomenon referred to as ‘spontaneous abortion’ in the medical world.) This varies by region and socioeconomic status, with the risk increasing with age.
That said, since most women don’t cotton on to the fact they are pregnant right away and most miscarriages occur within the first 12 weeks, many won’t even know it’s happened.
“[Miscarriage is] a natural and inevitable part of human reproduction at all ages,” Rice wrote in the paper.
“To reproduce, a human female cannot forgo a high risk of [spontaneous] abortions and to have a large family it is virtually impossible to avoid multiple [spontaneous abortions.”
“Modern birth control with access to elective abortions markedly reduces – rather than increases – the lifetime number of abortions a woman produces.”