The first meaning is 'metre' which is a measurement of length. If the 'm' stands alone it is metre. The second meaning is 'milliâ¦' which means a thousandth. In this case 'm' can not stand alone, we need to know what we have a thousandth of; if it is weight, length or some other thing. Example: mg means 'milligram', a thousandth of a gram. Example: mm means 'millimetre', a thousanth of a meter.
At about six weeks into pregnancy (four weeks from conception), you should be able to see your baby's heartbeat on ultrasound. The typical heart rate at this age is about 100 beats per minute.
you're baby's ears begin to form at around eight weeks and become structurally complete at about 24 weeks. But as early as 18 weeks, the bones of the inner ear and the nerve endings from the brain have developed enough for your baby to hear sounds such as your heartbeat and blood moving through the umbilical cord.