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.
Hearing your baby's heartbeat for the first time can be deeply moving. Keep in mind that a baby's heartbeat is much faster than an adult's. If you're in your first trimester and you can't hear your baby's heartbeat, don't worry. Dopplers can't reliably detect a baby's heartbeat until 10 to 12 weeks. Your doctor may try again on your next visit.