For years, knowledge about the development of the heart of an unborn child pegged the beginning of the beating of the heart at around 21 days after conception.
Now, new research finds that these first heartbeats occur at 16 days after conception. The Ottawa Citizen reported on October 13 :
“A human heart will beat some three billion times over an average lifespan, and now British scientists say its very first beat comes much earlier than anyone realized. The early stage of heart muscle starts beating in mouse fetuses 7.5 days after conception, which is the equivalent of 16 days after a human fetus is conceived.

The new study  comes from the University of Oxford. The British Heart Foundation, which funded the work, says about one in 180 UK babies has a congenital heart condition. By understanding how the heart develops in pregnancy, the researchers hope to improve the chances of treating these conditions at the earliest possible stage before a baby is born.

But the Oxford heart scientists say there’s a second reason to learn about the heart’s earliest days. It may help us decades later to recover from heart attacks.”