by Beverley Brooke
There are three stages of pregnancy. These are the first, second and third trimesters. The first trimester runs from week one to week fourteen, the second covers weeks 15 – 26, then the third is weeks 27 – 40.
Week 1+2: This is actually before you get pregnant. It’s the stage where your body prepares itself by ovulating. And it’s in these 14 days that the egg is fertilized by the sperm
Week 3: The fertilized egg now moves down the fallopian tubes, fluid passes into the ball of cells, dividing them into two. The inner cells will form your baby and the outer cells will form the placenta. Your body, at this stage, is still unaware that it is pregnant. The implantation begins as the cell ball reaches the wall of the uterus. In this process the cells actually bury into the uterus wall, which can sometimes lead to you having spotting. The implanted cell ball now becomes an embryo.
Week 4: This is a week of rapid development, and your body now realises it is pregnant. The amniotic sac and cavity begin to develop and also the Yoke sac appears (this will later form the baby’s digestive system). The placenta now starts to form where implantation took place and blood from you will now go into the placenta. It is usually about day 27 that we start to feel the morning sickness.
Week 5: The primitive streak (the fore runner of the brain and spinal cord) is now developing. Through this primitive streak the cells will develop into three layers:
The endoderm: the bottom layer – develops the glands, lung linings, tongue, bladder, digestive tract, tonsils, urethra and associated glands.
The mesoderm: the middle layer – forms the muscles, bones, heart, lungs, spleen, blood cells, and the reproductive and excretory systems.
The ectoderm: the top layer – forming the skin, nails, hair, eye lens, nose, mouth, anus, tooth enamel, pituitary gland, mammary glands, and all parts of the nervous system.
Other cells will be starting to develop the spine (called the notochord). The first steps towards forming the embryos head, and the first formation of the babies blood cells happen this week.
Week 6: The first few days of this week is when your baby’s heart starts beating. The aorta (the largest artery in the whole body) will be starting to form at around day 40. By mid week many organs are starting to form: eyes, arm buds, liver, gall bladder, stomach and intestines, lungs and pancreas.
Week 7: This is a busy week for your growing baby. During this week your baby will double in size. The lenses of the eyes are developing and there is also a recognisable tongue. The legs and arms are developing into paddles, the jaws are now visible.
Week 8: The cerebellum starts to form this week. That’s the part of the brain responsible for the movement of muscles. Also hand and foot plates, elbow and wrist areas are forming. Towards the end of the eight week the hand plate has formed ridges where the fingers will be. There is further development of the eye; pigment is now appearing
on the retina. Teeth buds are now forming within the gums, along with the wind pipe, bronchi, and voice box. The heart is now starting to develop the four chambers.
Week 9: Your baby is now starting to form cartilage and bones. During this week the ovaries will develop into the sex organ determining whether you’re having a boy or a girl. The fingers and thumbs are now taking shape. Also the baby is now becoming more active.
Week 10: It’s now that your embryo has become a baby, all be it on a rather small scale. There is a fully formed upper lip. The development of the heart now slows as it is past the critical stage. By mid week the earlobes are fully formed. Toes start to develop on the foot plate. As the bones of the palate (roof of the mouth) start to fuse together, the tongue starts to develop taste buds.
Week 11: as the morning sickness starts to subside, you may feel your appetite increase. Your baby’s body starts to straighten. In males the penis is now distinguishable and in females the vagina is beginning to develop. This stage is where the baby starts to show individuality, as the muscle structure varies in each baby.
Week 12: Your baby will start to develop fingernails over the next three weeks. The brain is now the same structure as it will be at birth. By the end of the week, the gall bladder and pancreas will be fully developed. Also the baby will now be opening and closing its mouth.
Week 13: This week vocal chords will form in the larynx. Also the intestines will move from the umbilical cord into the abdomen, and will start to form folds and become lined with villi.
Week 14: You may have noticed some changes to the areola (the area around your nipple); it may be getting larger and darker. Your baby’s heart beat will now be able to be heard using a Doppler. Breathing, sucking and swallowing motions will be being practiced. The breathing practices will take the amniotic fluid in and out of the lungs. Baby’s hand also becomes more functional.
Week 15: The baby’s neck is now defined, with the head now resting on the neck rather than the shoulders. The hair pattern of the baby will be defined by the 102nd day of the pregnancy your baby will now be able to turn its head, open its mouth, kick, press its lips together and turn its feet.
Week 16: This week the baby’s toe nails will start to grow. The muscles will be growing stronger and the neck and head are growing straighter. As the uterus starts moving upwards you may start showing more, but this does mean less pressure on your bladder, making you feel like urinating
less.
Week 17: Your baby will be working on more reflexes this week; blinking, sucking, and swallowing. Development is carrying on with all the existing structures. Through the course of this month your baby’s weight will increase 6 times.
Article by Beverley Brooke
Visit pregnancy week by week to ensure a healthy
pregnancy and for more on pregnancy week by week