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2 weeks
At the start of this week, The ovulation. The egg is fertilized 12 to 24 hours later if a sperm penetrates it – and this simple biological occurrence begins a series of increasingly complicated processes that leads to a new human life, if all goes well. Over the next several days, the fertilized egg will start dividing into multiple cells as it travels down the fallopian tube, enters The uterus, and starts to burrow into the uterine lining. -
3 weeks: impantation
Now nestled in the nutrient-rich lining of The uterus is a microscopic ball of hundreds of rapidly multiplying cells that will develop into The baby. This ball, called a blastocyst, has begun to produce the pregnancy hormone hCG, which tells your ovaries to stop releasing eggs -
4 weeks
The ball of cells is now officially an embryo. now about 4 weeks from the beginning of your last period. It's around this time – when your next period would normally be due – that might be able to get a positive result on a home pregnancy test. -
5 weeks
The baby resembles a tadpole more than a human, but is growing fast. The circulatory system is beginning to form, and the tiny heart will start to beat this week. -
6 weeks
The baby's nose, mouth and ears are starting to take shape, and the intestines and brain are beginning to develop -
7 weeks
The baby has doubled in size since last week, but still has a tail, which will soon disappear. Little hands and feet that look more like paddles are emerging from the developing arms and legs -
8 weeks
The baby has started moving around, though movement won't be quit feelable. Nerve cells are branching out, forming primitive neural pathways. Breathing tubes now extend from his throat to his developing lungs -
9 weeks
The baby's basic physiology is in place (she even has tiny earlobes), but there's much more to come. Her embryonic tail has disappeared. She weighs just a fraction of an ounce but is about to start gaining weight fast -
10 weeks
The embryo has completed the most critical portion of development. His skin is still translucent, but his tiny limbs can bend and fine details like nails are starting to form -
11 weeks
The baby is almost fully formed. She's kicking, stretching, and even hiccupping as her diaphragm develops, although you can't feel any activity yet -
12 weeks
This week The baby's reflexes kick in: His fingers will soon begin to open and close, toes will curl, and his mouth will make sucking movements. He'll feel it if you gently poke your tummy – though the mother won't feel his movements yet -
13 weeks
This is the last week of The first trimester. The baby's tiny fingers now have fingerprints, and her veins and organs are clearly visible through her skin. If having a girl, her ovaries contain more than 2 million eggs -
week 29
The baby's muscles and lungs are busy getting ready to function in the outside world, and his head is growing to make room for his developing brain -
20 weeks
20 weeks into pregnancy, The baby can swallow now and his digestive system is producing meconium, the dark, sticky goo that he'll pass in his first poop – either in his diaper or in the womb during delivery
