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.
A baby's heart begins to beat 18 days from conception, and by 21 days the heart is pumping blood through a closed circulatory system. A baby's brainwaves can be detected at 6 weeks from conception. At 8 weeks from conception, a baby's heartbeat can be detected by ultrasonic stethoscope. 2  By 9 weeks from conception, a baby is able to bend her fingers around an object in her hand. 3  By 11 to 12 weeks from conception, the baby is breathing fluid steadily and continues to do so until birth.