Pregnancy begins with conception. Two cells, a sperm and an egg, come together inside the uterus to make one cell. In a few hours, this single cell will divide itself over and over. This makes a cluster of cells that will become your baby. The tiny cluster must attach to the lining of the uterus. This happens in the first 2 weeks. Even before you know you are pregnant, the baby's nervous system, heart, and lungs have begun to develop.
Doctors measure pregnancy in weeks and months: 40 weeks, or 9 months total. The months of pregnancy are divided into three parts called "trimesters." The first trimester starts with your last menstrual period. Conception happens about two weeks after your period. Eight weeks after your last period, your baby's brain and spinal cord are developing, and its heart is beating. First trimester is an important time in the baby's development. That's why doctors recommend that you prepare your body before you get pregnant: no alcohol, no smoking, eat well, and exercise.
By the end of the first trimester at 12 weeks, the baby has fingernails and toenails. It's about 7.5cm and weighs 30 grams. Your doctor can let you listen to the baby's heartbeat with a special instrument.
The second trimester, from 13 to 24 weeks, is when the baby's bones and muscles develop. If you have an ultrasound done, you may see the baby suck its thumb. At about 20 weeks by dates, the baby (now called the foetus) begins to move. The first movements are felt as flutters and are known as "the quickening". These foetal movements, while they cannot be used as an accurate guide to dates, can be used as confirmation that dates are approximately correct. The movements are slight at first and may be mistaken for wind, but increase in strength as the baby grows. At the quickening, the top of the womb is about level with the mother's navel. Foetal movements are often detected earlier in second and subsequent pregnancies as the experienced mother is less likely to attribute them to "wind" and her uterine muscles are softer following a previous pregnancy. By the end of the sixth month, the baby may be 30cm long and weigh about a kilogram.
The third trimester, from 25 to 40 weeks, is the longest. During this time the baby grows longer and heavier. It begins to practise breathing motions and open its eyes. The baby can hear sounds. It responds to familiar voices. From 37 weeks on, the baby is ready to be born. The average full-term baby weighs around 3 to 3.5 kilograms and is 50cm long.
Pregnancy is also divided into two segments, less than 20 weeks and more than 20 weeks. Isn't it amazing to think that each new baby started as two tiny cells?
Take care of yourself and your baby. If you have questions about your pregnancy, or about your baby's development, talk with your doctor or midwife.
Article #4887
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