Fetal Development - Week by week from 1 to 40 (2023)

How is my baby growing? – A weekly review of fetal development

For many women, pregnancy and childbirth are a turning point in their lives. Some people who have been there might even say it was one of their most rewarding experiences. As a mom-to-be I can tell you are curious, believe me this is normal. You bought the books, you watched the videos; You are reading this article right now. I get it: you can't wait to meet your son and you want to be ready when he arrives. Well I'm glad you're here! In this post, we will discuss the different stages of fetal development on a weekly basis.

prenatal development

Prenatal development describes the entire development process of the baby, from menstrual age to fertilization and birth. Prenatal development occurs in three stages: the germinal stage, the embryonic stage, and the fetal stage.

the germination stage

Fetal development begins with the germinal stage. This counts from the day of your last menstrual period and lasts about three weeks. In case you didn't know, conception is not the beginning of your pregnancy; All the work your body has done to make fertilization possible must be worth something. Although pregnancies typically last around forty weeks, you are actually only thirty-eight of those weeks pregnant. This is because your pregnancy starts counting from the first day of your last menstrual period. Now let's take a closer look.

(Video) Pregnancy Week By Week || 1 - 41 Weeks Fetal Developments

Week 1:You see your period. This is your body shedding the uterine lining and preparing to start a new menstrual cycle. At the end of this week, your period will end and your body will start producing more hormones.

week 2:Your estrogen and progesterone levels are at their peak and this causes the lining of the uterus to thicken. As this happens, your eggs "mature" in fluid-filled sacs commonly called follicles. As the second week comes to an end, your body will release another hormone (lutrophin). This hormone causes the follicles to rupture, releasing the egg/ovum (or egg/ovum) into the fallopian tube to reach the uterus. The process we have just described is what you have always referred to as ovulation. (It's important to note that while ovulation typically occurs in the middle of the menstrual cycle, this is not always the case. Ovulation can occur anytime between nine and twenty-one days after the first day of the last menstrual period.)

It usually takes a day or two for the egg to travel from the ovaries to the uterus. If one of the many sperm released during ejaculation succeeds in penetrating the egg on its way to the uterus, fertilization occurs. Over the next 48 hours, the sperm fuses with the egg and their DNA combines to form a zygote.

At the end of the second week, the zygote continues its journey from the fallopian tube to the uterus. As it travels, it will continue to divide into hundreds of identical cells. In about two days, the zygote (which is now a blastocyst) attaches to the uterine wall. The end of the second week also marks the end of the germination stage.

the embryonic stage

The embryonic stage lasts about eight weeks after fertilization. This phase is very important for the development of brain function. It is therefore important to eat properly during this phase.

(Video) 40 Weeks In The Womb by Ultrasound Dimensions

week 3:Starting this week, you will likely get a positive pregnancy test. The blastocyst continues to divide and burrow further into the uterine wall. The inner cells of the blastocyst develop into the embryo, while the outer cells grow into the embryo. The outer cells begin producing human chorionic gonadotropin (hCG), also known as the pregnancy hormone. The pregnancy hormone is the one detected when you urinate onto a stick. This hormone also tells your ovaries to stop releasing eggs and progesterone.

Week 4:Your tiny embryo is now the size of a poppy seed. The inner cells are divided into three further layers. The first layer develops into the digestive and respiratory systems (stomach, lungs, bladder, etc.). The middle layer develops into the circulatory, muscular, and skeletal systems, while the outer layer develops into the nervous system, eyes, teeth, skin, and nails. Before the placenta is fully formed, the embryo receives nutrients and excretes waste through a yolk sac. Later in pregnancy, the placenta forms and replaces the yolk sac.

Week 5:At this time, the baby's heart and nervous system began to develop. You should start taking folic acid at this stage as it can prevent a condition called spina bifida in your baby. Spina bifida is a condition where the baby's spine and spinal cord are underdeveloped, creating a gap in the spine.

Week 6:At this stage, the embryo appears to have a tail. Your baby's heart is still developing, while their tiny arms and legs are also starting to grow like cocoons.

Week 7:Your baby is now about 10mm long and the brain continues to develop rapidly. His inner ears and eyes also began to develop. The limb buds enlarge and begin to form cartilage, which becomes the bones of the limbs.

Week 8:Your baby is now the size of a bean and weighs about 1.13 grams. Still small, right? I know. Although the lower extremities lengthen, they are still indistinguishable. Your baby now has fingers and toes and his respiratory system is developing. The eighth week is the end of the embryonic stage. After this week your pregnancy will enter its longest and final phase; the stage of fetal development.

(Video) Pregnancy week by week 1 to 40 | Watch the Movements of Your Baby

a fetal stage

The fetal stage is the longest and probably the most dramatic stage of prenatal development. When fetal development begins, cell differentiation is complete and the baby is no longer referred to as an embryo but as a fetus. We will now discuss this further and look at the development per week.

Week 9:At this point, your baby has almost all the vital organs and looks like a really small person. All of your baby's heart chambers have formed and baby teeth have started to grow. By week 9, the placenta is almost fully developed and ready to replace the yolk sac.

Week 10:Your baby is now about 3.5mm long and their outer ears have started to develop. The channels between the inner and outer ear also form. The jawbones are developing and your baby's heart is pumping and beating hard. Although the eyelids also begin to form, they remain closed until week 27. At this point, the placenta should be fully formed and the yolk sac should shrink until it is completely dissolved. In some people, the placenta may not take over until the 20th week.

Week 11:Your baby is now the size of a fig. The facial bones are sculpted and the outer ears now look more like ears. His fingers and toes separate and his external genitalia begin to develop at this point.

Week 12:You are approaching the end of the third month and your baby is about the size of a lemon. It is now 57mm long and weighs about 14 grams. Your baby has started to develop reflexes and can now curl their toes. The intestines are now fully developed and placed in the abdominal cavity. The external sex organs must be well developed along with all other organs. Now your baby just needs to grow.

(Video) (১ ম সপ্তাহ - ৪০ সপ্তাহ )/(1st Week - 40th Week) Baby During Pregnency

Week 12 is the end of the first trimester of pregnancy. The most critical period in your baby's development is over, and you'll be less likely to miscarry after that time.

Week 13-15:This is the start of the second trimester. You can now hear your baby's heartbeat. His fingers and toes are well defined and his bones have become denser. Eyebrows, eyelashes, fingernails and toenails are formed around this time. Now your baby can stretch, yawn and even make faces. At the end of the 15th week, they are about 152 mm long and weigh 113 grams. Their external genitalia are fully formed and now you can find out your baby's sex through an ultrasound.

Week 16-19:If you haven't told them already, I'm sure your friends and family already know you're pregnant. Your baby is now developing muscles and you can feel them moving as you exercise them. Your baby is covered in cheese goo, a white substance that protects your baby from prolonged contact with amniotic fluid. Don't worry, they'll shed that coat just before birth. By now your baby should be around 25cm long and weigh around 250 grams.

Week 20-23:It's nearing the end of the second quarter. Congratulations! you are almost there Your baby now has fingerprints and you can see his veins through his translucent skin. Those earlier small movements turned into full kicks.

Week 24-29:This is the beginning of the third and final trimester. Now that his hearing is fully developed, you may want to sing to him from time to time. They can also respond to stimuli, so you may notice that they often change position in response to light or sound. During this time, the amniotic fluid begins to decrease. Your eyelids also open around this time. By the end of the 29th week, your baby should weigh between 900g and 1.5kg.

Week 30-35:Your baby is beginning to build up body fat stores. They can see it, they can hear it, and now they're fighting it even more. Its brain and all internal organs are almost fully developed. However, their lungs still need some time to fully mature. Your baby should now weigh around 2 kg.

(Video) pregnancy week by week 1-40

Week 35-40:Is this! You've come this far, your baby is almost here. Their lungs are fully developed and their reflexes are more coordinated, allowing them to blink their eyes, turn their heads, and even pick up objects. As your due date approaches, you may notice that your baby is moving less. Don't panic, there's less space for that now! As you approach 40 weeks, your baby will begin to position himself for birth. The head looks down and falls into the pool. Now your baby weighs about 3 kg and is ready to be born!


What happens to fetal development from 1 week to 40 weeks in mother womb? ›

The beginning of the spinal cord, muscles, and nerves become apparent. Arms, legs, eyes and ears can now be seen. The amniotic sac and placenta are in place and providing nourishment to the embryo. The eyes begin to form and the extremities can be seen in much more detail, including all ten fingers.

What are the most critical weeks of fetal development? ›

First Trimester (0 to 13 Weeks)

The first trimester is the most crucial to your baby's development. During this period, your baby's body structure and organ systems develop. Most miscarriages and birth defects occur during this period. Your body also undergoes major changes during the first trimester.

At what week is baby mostly developed? ›

Week 31: Baby's rapid weight gain begins

Thirty-one weeks into your pregnancy, or 29 weeks after conception, your baby has finished most of his or her major development.

What are the stages of fetal development in order? ›

There are three stages of prenatal development: germinal, embryonic, and fetal. Keep in mind that this is different than the three trimesters of pregnancy.

What causes a baby to be overdue? ›

You are more likely to be overdue if you are obese, have never given birth before or if you're over the age of 30. Your midwife or doctor will check that both you and your baby are healthy by giving you ultrasound scans and checking your baby's movement and heartbeat.

What does it mean if your baby is very active in the womb at night? ›

A number of ultrasound and animal studies have shown that the fetus has a circadian pattern that involves increased movement in the evening, and this is likely to reflect normal development.”

What is fetal development at 40 weeks? ›

40 Weeks Pregnant: Your Baby's Development

Your baby's head has likely dropped lower into your pelvis, and his body is curled up tightly. He doesn't have much choice — it's pretty crowded in there.

Is the baby fully developed at 40 weeks? ›

Optimum Health

A full-term pregnancy also benefits your baby after labor. The brain is only two-thirds developed before 37 weeks, and the lungs, liver and muscles will be more fully developed at 40 weeks, as well. Babies who are born at term also tend to suck and swallow more effectively, making breastfeeding easier.

What is the organ called that the fetus grow in for 40 weeks during pregnancy? ›

Uterus. The uterus, or womb, is a hollow, pear-shaped organ ln a woman's lower stomach between the bladder and the rectum. It sheds its lining each month during menstruation. A fertilized egg (ovum) becomes implanted in the uterus, and the fetus develops.

How is the baby in 40 weeks of pregnancy? ›

weighs about 3.5 kg, ranging from 2.9 kg to 4.2 kg. measures about 50 cm from head to toe, ranging from 46 cm to 56 cm. has a head circumference of about 35 cm, ranging from 33 cm to 37 cm.


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