This didnt work for me as first time heart was 138 and second was 128 (the midwife said the wives tale goes that 120-140 is a boy and 140-160 is a girl so she reckoned I was having a boy, but had to get a amnio done due to high blood results, when it came back clear I asked the sex and they said it was a girl, so this theory did not work for me.