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.
Typically the heart beat can not be heard with even a doppler until the 9-10th week of pregnancy at the very earliest (sometimes not until the 12-14th weeks of pregnancy). A baby's heart beat is very rapid, much faster than an adult. In fact it starts out near 180 beats per minute (BPM) and around 12 weeks gestation settles into the normal range of 120-160 BPM for the remainder of the pregnancy. Even though you can not hear the fetal heartbeat until week 9 or 10, ultrasound is able to see a beating heart much sooner.