7 Fascinating Facts About the Human Heart

It’s a Myth That Heart Rate Can Reveal the Sex of an Unborn Baby

The heart is the first organ to develop in a human embryo. The earliest rudimentary form of the muscle, called the tubular heart, starts beating about three weeks after conception. By the fifth week of gestation, a healthy fetus’s heart rate averages 110 beats per minute, increasing to 170 beats by the ninth week. It slows to 150 beats on average by the 13th week. It was once thought that an unborn baby’s sex could be determined based on its heart rate as detected by an ultrasound, but studies have shown there is no significant difference between boys’ and girls’ fetal heart rates.

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