Pregnancy Week by Week
Although pregnancy involves a continuous process, it is divided into three 3-month periods called trimesters (weeks 0 to 12, 13 to 24, and 25 to delivery).
1st Trimester
| Your last period before ferilization occurs | Week 0 |
| Fertilization/conception occur when your ovum (egg) is fertilised by your partner's sperm. The gender and inherited characteristics are decided in that instant | Conception |
| Cell splits into two 30 hours after conception, on day 3 the cell (zygote) has divided into 16 cells, on day 5 the cell has migrated from the fallopian tube to the uterus | Week 1 |
| The fertilized egg (zygote) begins to develop into a hollow ball of cells called the blastocyst. Your developing baby is tinier than a grain of rice. The rapidly dividing cells are in the process of forming various body systems. | Week 2 |
| The blastocyst implants in the plump lining of the uterus (endometrium). The amniotic sac begins to form. The evolving neural tube, which will eventually become the central nervous system (brain and spinal cord), starts to form | Week 3 |
| Hormones are being secreted that prevent you from having a menstrual period. Your baby is now known as an embryo and is around 3mm in length | Week 4 |
| The heart and major blood vessels are developing. The beating heart can be seen during ultrasonography. The placenta and anmiotic sac are already developing, and the placenta continues to burrow into the uterine wall to access oxygen and nutrients from your bloodsteam | Week 5 |
| Your baby's head is disproportionately large and the rapidly growing spinal cord looks like a tail. Your baby, who is still an embryo, is now around 1.3cm in length | Week 6 |
| The beginnings of arms and legs appear. Bones and muscles form and the face and neck develop. The eyes, mouth and tongue are forming. Tiny muscles allow the embryo to start moving about. Blood cells are made by the embryo's liver | Week 7 |
| The embryo is now known as a foetus and is about 2.5cm in length. Almost all the bodily organs are completely formed. The brain is active and brain waves can be detected. The hands and feet are now evolving fingers and toes | Week 8 |
| Teeth are budding inside the gums. Kidneys begin to function | Week 9 |
| Little fingers and toes are recognisable, but still stuck together with webs of skin. The foetus can move and respond to touch (when prodded through mommy's abdomen) | Week 10 |
| The foetus can swim about quite vigorously and is now more than 7cm in length | Week 11 |
| The eyelids are fused over the fully developed eyes. Your baby can mutely cry, since vocal cords have developed and might even start to suck on a tiny thumb. Fingers and toes are growing nails. Mommy has gained some weight, and your abdomen may be slightly enlarged | Week 12 |
Week 1-4
Week 5-8
Week 9-12
2nd Trimester
| The muscles develop furhter, and your baby's movements are more coordinated. The foetus' fingers can grasp | Week 14 |
| The foetus is around 14cm in length. Eyelashes and eyebrows have appeared and tastebuds developed on the tongue. The foetus moves more vigorously and can be felt by mommy. The foetus' body begins to fill out as fat is deposited beneath the skin | Week 16 |
| An ultrasound (scan) is commonly performed around this time to check for abnormalities, the position of the placenta and for the possibility of a multiple pregnancy. It is nomal for the foetus to have hiccups | Week 18 |
| The foetus is around 21cm in length. The ears are fully functional and muffled sounds from the outside world might be audible. The fingertips have prints. The genitals can now be distinguised with an ultrasound scan | Week 20 |
| The placenta is fully formed. The fetus has a chance of survival outside the uterus. The foetus is around 33cm in length. The fused eyelids are now seperated into upper and lower lids, enabling you baby to open and shut his eyes. The skin is covered in fine hair (lanugo) and protected by a layer of waxy secretion (vernix). The baby "breathes" amniotic fluid in and out of his lungs | Week 24 |
Week 13-16
Week 17-20
Week 21-24
3rd Trimester
| Your foetus is around 37cm in length. The fast growing body has cought up with the large head and the foetus seems to be proportioned more correctly | Week 28 |
| Your baby spends most of her time asleep. Her movements are strong and coordinated. She has probably assumed the 'head down' position by now, in preparation for birth | Week 32 |
| On average your baby is around 45cm long and weighs about 3.1kg. She has probably nestled her head into your pelvis, ready for birth. Development of her lungs is rapid over the next few weeks. If she is born now, her chances for survival are excellent. Mommy's enlarged abdomen causes the navel to bulge | Week 36 |
| Your baby is around 51cm in lenght and ready to be born. Your body, when it's ready, secretes hormones that trigger the onset of labour | Week 38-42 |
Week 25-28
Week 29-32
Week 33-36
