Your body, as well as that of your growing baby, undergoes many changes during your pregnancy. Take a closer peek at what’s going on each week with our fetal development timeline.
Throughout the pregnancy process, your child will transform from a tiny fertilized egg, to a fully-formed baby. Here, we answer some questions you may have about your baby’s major milestones during pregnancy, with a general week-by-week guide on fetal development.
While we’ve made it easy for you to track developments throughout your pregnancy, please keep in mind that the week-by-week guide is only an estimate, and is therefore not definitive. Every woman’s body may experience these milestones at different times.
Development: Right now, your baby is a ball of cells called a blastocyst. The blastocyst contains DNA from you and your husband, which determines sex, eye color, and other features.
Development: During this time, your baby is transforming from your little ball of cells called blastocyst to an embryo. Also, his organs will begin to take shape in the next 6 weeks.
Development: Not only is your baby’s heart starting to beat, it beats at twice the rate of yours.
Development: Your baby’s facial features are beginning to form. Eyes and nostrils are forming, and stumps are appearing where their arms and legs will be.
Development: Little hands and feet that look more like paddles are emerging from the developing arms and legs.
Development: Arms and legs are growing, and your baby now has little fingers, as well as a nose and upper lip. You won’t feel it yet, but your baby will start to move now too.
Development: Even though your baby’s eyes are fully developed, their eyelids are still closed. They will open around week 28.
Development: Vital organs like the kidneys, intestines, brain and liver are starting to work. Nails are also visible at this stage. Your baby’s skin is still see-through, but his limbs can move and bend. Your baby’s fingerprints are also developing now.
Development: Your baby is almost a baby in every sense of the word, kicking and stretching. He will soon begin to hiccup, which is something that occurs as his diaphragm develops. You won’t be able to feel hiccups until week 27.
If you poke your 12-week pregnant belly while looking at him on the ultrasound during the prenatal checkup, you’ll likely see movement.
Development: Also, during week 12, your baby’s reflexes start to work. Their fingers will soon begin to open and close, their toes will start to curl, and mouth will make sucking movements.
Development: Your baby is beginning to make urine and release it into the amniotic sac, making amniotic fluid. Bone now replaces tissue around your baby’s head and inside arms and legs. His first fingerprints also take shape. Veins and organs can be seen through the skin.
Development: Your baby’s kidneys are working, his arms have almost reached the final relative lengths they’ll be at birth and his neck has become more defined.
Development: Your baby is growing rapidly. His skeleton is developing bones, which will become visible on ultrasound images in a few weeks. His scalp hair pattern is also forming.
Development: Your baby’s eyes have begun to face forward and slowly move. his legs are more developed and his head is more upright.
Development: Your baby’s toenails have begun to develop. Soon fat stores begin to develop under your baby’s skin which will provide energy and help keep him warm after birth. The umbilical cord is growing stronger and thicker.
Development: Your baby’s ears begin to stand out on the sides of his head. He might also begin to hear your voice. Internally, your baby is producing myelin, a protective coating that surrounds some nerve cells, forming an electrically insulating layer that is essential for the proper functioning of the nervous system.
Development: A special coating begins to cover your baby. This coating helps protect your baby’s delicate skin from ailments that can result from exposure to the fluid that surrounds him. Your baby’s senses – smell, vision, touch, taste and hearing – are developing. He may even be able to hear your voice.
Development: You are now halfway through your pregnancy. At this stage, you might be able to feel your baby’s movements. Your baby can swallow now and his digestive system is producing meconium: the dark, sticky goo that will pass in their first poop.
Development: Your baby’s movements have gone from slight to full-swinging kicks and jabs against the walls of your womb. You may also start to notice patterns to the movements; for example, more movements after eating.
Development: Your baby’s skin is completely covered with protective fine hair at this stage, which will fall off shortly after they are born.
Development: Your baby’s skin is wrinkled and will smooth out as he grows. Your baby’s tongue will soon develop taste buds and his ears are steadily getting better at picking up sounds.
Development: Your baby is regularly sleeping and waking. Real hair is growing on his head. His skin is still see-through, but that will begin to change soon.
Development: Your baby’s hands and reflexes continue to develop as well as his ability to respond to familiar sounds. Also, his hair is beginning to fill with colour and texture.
Development: Your baby’s lungs are now beginning to work. They are currently breathing amniotic fluid in and out as practice for when he has to breathe in air as soon as he is born.
Development: This is the last week of your second trimester. Your baby’s sleep patterns are now regular. His brain is now very active and although his lungs aren’t fully developed, they can already function on their own.
Development: His eyelids can now open and they will start to blink. As his brain develops and eyesight improves, your baby might be able to sense light from outside.
Development: Your baby’s muscles and lungs are equipping themselves with what they will need when he exits to the outside world. His head is growing to make room for his developing brain.
Development: Your baby is claiming more space inside your uterus. He is surrounded by approximately 500ml of amniotic fluid.
Development: Your baby can now turn his head from side to side. A protective layer of fat is accumulating under his skin, filling out his arms and legs.
Development: During this period, your baby’s nails will begin to grow, and he will continue to develop in preparation for his birth.
Development: The bones in your baby’s skull aren’t fused yet, which means he still can’t fit through the birth canal.
Development: Your baby’s skin has become soft and smooth and his central nervous system is constantly maturing, as are his lungs.
Development: It’s getting snug for your baby inside your womb – it’s almost time to come out. Your baby’s kidneys are fully developed, and his liver can start processing.
Development: Your baby is gaining about an ounce a day and is also starting to lose the fine hair on his body as well as the waxy substance that protected his skin.
Development: If your baby is born this week, he might still have a little fine hair on his body, but his lungs are more than likely capable of adjusting to life outside the womb.
Development: At 38 weeks, you are almost at full term. The only remaining part of the pregnancy journey is meeting mum and dad.
Development: Your baby is practically full term this week, however he continues to build a layer of fat, which will help him to control his body temperature after birth.
Development: You still have a couple of weeks before you’ll be considered “post-term.” But to be sure your baby is still thriving, your doctor will perform tests to make sure you can safely continue your pregnancy.
Development: If your baby hasn’t been born by week 41, their health might start being monitored. Your doctor may decide to induce labour.
Please note that these comparisons are only provided to give a broad reference for visualizing your baby’s size throughout the pregnancy period. If you have any queries or concerns about your baby’s development, please consult your doctor directly for more information.