Fetal development begins immediately after conception, so here's a
stage of pregnancy by week that will tell you what to expect as your baby grows with you throughout the 40-week pregnancy!
Read more: 17 Pregnancy Do's and Don'ts You May Not Know
First Trimester
Pregnancy 1 Week
As strange as it may sound, you are not pregnant in the first week because it is your
menstrual period. This week, however, counts as part of your pregnancy because your due date is calculated from the first day of your last period, even if you haven't conceived yet.
Pregnancy 2 Weeks
Because ovulation occurs around day 14 of your menstrual cycle, this is the best time for fertilization to occur. And if the sperm successfully meets the egg, you've got a bun in the oven!
Pregnancy 3 Weeks
Your newly fertilized egg, known as a zygote, will now travel from your fallopian tube to the uterus in just a few hours. At the same time, it will begin to divide into a cluster of cells known as a blastocyst.
Pregnancy 4 Weeks
Once inside the uterus, the rapidly dividing cells will burrow into the uterine lining and separate into two parts: the embryo and the placenta. Your developing baby is only about the size of a grain of rice at this point.
Pregnancy 5 Weeks
The fifth week of pregnancy is when your embryo begins to form the umbilical cord and other vital organs, including the neural tube, which is where the baby's brain and spinal cord will develop. Morning sickness, spotting, and food cravings may occur as a result of rising hormone levels.
Pregnancy 6 Weeks
Your baby is now around 4 to 7mm in size and is developing facial features such as ears, mouth, and ears. Expect temporary discomforts such as nausea, mood swings, and fatigue. You may also notice that your breasts are feeling extra tender these days, which is because you're getting ready to breastfeed.
Pregnancy 7 Weeks
Your baby, now about the size of a pea at 1cm, has more defined facial features as well as developing limbs that will divide into hands, arms, and feet. Your baby bump is probably not visible yet, but you might go up a bra size or two!
Pregnancy 8 Weeks
A growth spurt is underway! Retinas begin to color, and bones begin to form quickly, forming knees, ankles, wrists, and elbows.
Pregnancy 9 Weeks
Your baby is nearly an inch long now and is constantly making tiny movements in your belly, though you can't really feel them yet. An ultrasound, on the other hand, may allow you to hear her heartbeat!
Pregnancy 10 Weeks
Congratulations, your embryo has completed the most critical stage of development and is now officially a fetus measuring around 3cm! Bone structures have formed, and organs are beginning to erupt.
Pregnancy 11 Weeks
It's now the size of a ping-pong ball! No more webbed fingers and toes; your child's hands will soon be able to open and close into fists. Tiny tooth buds appear beneath the gums, and hair follicles form on the scalp. Your baby's boy/girl bits will also begin to develop by the end of this week.
Pregnancy 12 Weeks
Your plump baby's digestive system is fully functional, and her kidneys are producing urine. This is also the week when she will develop the Moro reflex, which means she will be able to hear and respond to stimuli - try talking to her or singing a lullaby!
Pregnancy 13 Weeks
You've arrived at the end of the first trimester! Your baby's intestines will begin to shift from the umbilical cord to the belly when he or she is about 7cm long. Your placenta is fully developed and has all of the structures required to support the baby's growing needs, though it will continue to grow larger throughout the pregnancy. Is that a baby bump we see?
Second Trimester
Pregnancy 14 Weeks
The start of trimester two is probably what most mamas are looking forward to the most, as symptoms like morning sickness and sore nipples will begin to subside. And look how your baby can now make different facial expressions!
Pregnancy 15 Weeks
Guess what? Your baby can detect bright lights and is learning to breathe. Do you have a runny nose? It's a common side effect caused by high levels of pregnancy hormones in your body, which increases blood flow to membranes and causes your nose to become congested.
Pregnancy 16 Weeks
Another growth spurt is expected in the coming weeks. Despite the fact that your fetus is currently the size of an avocado, it won't be long before it doubles in size.
Pregnancy 17 Weeks
As your baby gains weight in utero, you may notice a significant weight gain during this stage. Aside from your belly, your milk-producing glands are expanding in preparation for lactation.
Pregnancy 18 Weeks
Your baby's genitals are now developed enough to be seen on an ultrasound scan, which will help you determine whether it's a boy or a girl. If you're lucky, you might even catch them having hiccups for the first time!
Pregnancy 19 Weeks
With the growth spurt complete, your baby is now roughly the size of a tomato and weighs around 240g. She's also developing more pigmentation on her translucent skin, thanks to melanin-producing skin cells.
Pregnancy 20 Weeks
We're halfway there! You will notice that she is swallowing more and producing more meconium in the intestines, which is a sticky, dark green fecal matter that a newborn baby passes shortly after birth.
Pregnancy 21 Weeks
Don't be alarmed by your baby's kung-fu kicks! In fact, now that she's gaining control of her limbs, you'll notice a lot more movement. Her taste buds are also developing, and here's an interesting fact: what you've eaten can actually affect the taste of the amniotic fluid that she swallows on a daily basis.
Pregnancy 22 Weeks
At 22 weeks, your baby will have distinct features such as eyelids, brows, and lips. Although she is still developing, she is beginning to resemble a tiny human being.
Pregnancy 23 Weeks
She can now make breathing movements as her lungs mature, and you can even try hearing her heartbeat with a stethoscope!
Pregnancy 24 Weeks
Your baby weighs 600g and is a foot long, while your uterus expands to the size of a soccer ball.
Pregnancy 25 Weeks
As your blossoming baby begins to grow more peach fuzz, your crowning glory may begin to look extra luscious and thick as well.
Pregnancy 26 Weeks
Now that your baby is more aware of her surroundings, she will learn to recognize voices from outside the womb and may even respond positively with some playful kicks. Studies have also shown that a fetus' heart rate increases when they hear familiar sounds, particularly the mother's voice, so talk to your baby often!
Third Trimester
Pregnancy 27 Weeks
Welcome to the third and final trimester, where you'll be greeted by an adorable fetus the size of a head of cauliflower. Babies at this stage have adapted to a regular sleep cycle, which means they can be extremely hyperactive when awake. Did we mention they like sucking their fingers?
Pregnancy 28 Weeks
Your baby now has well-developed eyes with newly grown eyelashes. She can not only blink and flutter her lashes, but she can also see light filtering through your womb.
Pregnancy 29 Weeks
A fetus' brain development is at its peak here, and its ability to interpret sights and sounds will become more apparent. This means your baby may be moving around and kicking more vigorously, often in response to stimuli.
Pregnancy 30 Weeks
Your unborn child will appear more proportionate at 30 weeks, though the head will still be larger than the body. Meanwhile, those dreaded first-trimester symptoms, such as mood swings, heartburn, and fatigue, are likely to reappear.
Pregnancy 31 Weeks
From swallowing to sucking and breathing, your baby is actively learning essential life skills. It's no surprise that her erratic movements will keep you awake at night, but you may also experience Braxton Hicks contractions, which are often described as uterine muscle tightening. Before you get too excited, these contractions are simply your body preparing for labor.
Pregnancy 32 Weeks
Boy, is she filling out! As your baby's system prepares for her first breastfeeding, some mothers-to-be may begin to leak colostrum from their breasts, which can be a messy situation, but a couple of nursing pads will help to soak it all up in no time.
Pregnancy 33 Weeks
Your baby has grown so large, weighing close to 2kg, that she probably takes up more space than the amniotic fluid inside your uterus. Her bones will harden, and she will eventually develop her own immune system.
Pregnancy 34 Weeks
This little rock melon has grown to around 46cm in length and is almost ready to give birth. Even if she decides to pop anytime this week, your newborn will be fine after a few days in intensive care.
Pregnancy 35 Weeks
Her brain is still rapidly developing at this point, but most of her physical development will be completed within the next few weeks.
Pregnancy 36 Weeks
As the due date approaches, your baby's head should have dropped further into your pelvis. By then, the pressure on your diaphragm will be significantly reduced, and your stomach will not feel as constricted.
Pregnancy 37 Weeks
During the final stages of your pregnancy, you may notice that your nipples protrude more than usual, which actually helps your newborn latch on better.
Pregnancy 38 Weeks
Your baby is now 3kg and half a meter long. Just a few more final developments on her brain, lungs, and nervous system, and she'll be ready to go!
Pregnancy 39 Weeks
As a full-term baby, your little watermelon is preparing for the big day. If your water breaks before you go into labor, call your doctor right away.
Pregnancy 40 Weeks
Your pregnancy has officially ended at 40 weeks. Your baby is about the size of a small pumpkin and weighs about 3.5kg. What you'll notice is that your newborn will continue to curl up in the fetal position; swaddling and talking to her will help to comfort her as she adjusts to the outside world.
Pregnancy 41 and 42 Weeks
Don't worry if you're still pregnant; approximately 30% of pregnancies last longer than the standard 40 weeks, which can easily lead to a miscalculation of the expected due date. When the baby is ready to meet the world, hormones are released to initiate labor. However, because overdue infants tend to appear larger than other newborns, you may be required to have a c-section if it becomes too large for a vaginal birth. Doctors may also recommend other methods of inducing labor to get your baby out, so just hang in there!
