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: Your baby's ears begin to grow when you're about eight weeks pregnant and are completely formed by about 24 weeks. But your baby can start hearing her first sounds -- like your heartbeat or blood whooshing through the umbilical cord -- around 18 weeks, when the bones of the inner ear and the nerve endings from the brain are developed enough. She may even be startled by loud noises!