Such sex 'distorters' have been discovered - and studied in great depth - in laboratory animals such as mice and flies, in which their effects can be detected through selective breeding. 'If you look, more often than not, you find them,' says Nitin Phadnis, an evolutionary geneticist at the University of Utah in Salt Lake City, who co-led the study.
I was already a mother of three when I lay back for my 10-week ultrasound in 2019. At first, seeing the gel on my stomach and the flickering black and white image on screen was familiar and soothing. Then I saw the look on the sonographer's face. She dropped the probe and ran out of the room without a word.