Fetus Development Month By Month

Every couple, from the beginning of pregnancy to the moment of birth is interested in knowing the fetus’s developmental stages week by week.

Pregnancy is special, attractive, and important for every pregnant mother. Awareness of more and more women during this period helps them go through a tortuous path during these nine months in perfect health, which will eventually lead to the birth of a healthy and loving baby. Body changes during pregnancy, fetal growth, and development during these weeks, advice and natural body signs are important to pregnant mothers.

Conception to birth

Pregnant mothers notice major and minor changes in their bodies after a few weeks. But as the baby progresses from the sperm and egg stage to the embryo stage, then to the fetus, and finally to the newborn, many magical events occur.

Over the nine months, many complex systems of the baby’s body are formed in their own specific timing, leading to the development of the baby’s body from the first heartbeat to hearing the mother’s voice inside the womb.

Using a pregnancy calendar by pregnancy due date calculator is a great way to gather information about how your baby is growing according to the weeks of pregnancy. Although each mother and baby’s condition is unique, all babies go through a specific and predictable process of pregnancy.

The pregnant mother will feel confident knowing that she has a common experience with other pregnant women and what she feels has been experienced by countless women in the past and future generations.

During pregnancy, new changes occur every week. The child changes day by day. The mother’s body also adapts to these changes. Obstetricians can tell the mother about changes inside and outside the body using a weekly pregnancy calendar. In general, these calendars contain information about the weekly changes that occur during the pregnancy for the baby.

When does pregnancy start?

The onset of pregnancy is the first day of the last menstrual period. This is called gestational age. Strange as it may seem, the due date of the first day of the last period will be an important date in determining the child’s due date. Obstetricians ask for this date and use it to determine the age of the fetus.

What happens right after conception?

Within 24 hours after fertilization, the egg divides rapidly into many cells. Remains in the fallopian tube for approximately three days. The fertilized egg (blastocyst) is then slowly transferred to the uterus through the fallopian tube, where it attaches to the endometrium, called implantation.

Before implantation, the blastocyst is removed from its protective coating. When a blastocyst interacts with the endometrium, two exchange hormones help bind the blastocysts. Some women notice spotting within a day or two of fertilization, which is normal.

Within three weeks, the blastocyst cells eventually form a small ball or embryo. By this time, the baby’s first nerve cells have formed. Generally, your baby is called an embryo from conception until the eighth week of development. After the eighth week, the baby is called a fetus until birth.

First trimester

You have decided to become a mother and prepare yourself for a long journey of 9 months. It is good to know that you are not aware of it until the miss your period next month and you hear the good news of your pregnancy with a pregnancy test. When you find out you’re pregnant, you are in the 4th or 5th week of pregnancy, but it is better to know about this 9-month trip from the beginning.

The first trimester of pregnancy will last up to 12 weeks. The first trimester of pregnancy is the beginning of the formation and growth of the fetus. During this trimester, the baby changes from a small group of cells to a fetus with baby characteristics.

Month 1 (weeks 1 through 4)

As the fertilized egg grows, a sac forms around it, gradually filling with an amniotic sac. During this time, the placenta is also developed. The placenta carries nutrients from the mother to the baby and the waste products from the baby. Throughout pregnancy, the placenta serves as a food source for the baby.

In these first few weeks, the primitive face forms large dark circles for the eyes. The mouth, mandible, and throat are developing. Blood cells form, and blood circulation begins. The small “heart” tube beats 65 times per minute by the end of the fourth week. By the end of the first month, your baby is about 1/4-inch long, smaller than a rice grain.

Month 2 (weeks 5 through 8)

During this month, the baby becomes a fetus. The baby’s facial features continue to develop, and the heart begins to beat. The baby’s internal organs, including the brain and spinal cord, are formed. The tiny buds that eventually turn into arms and legs form with those toes.

Because these important structures are developing, taking prenatal vitamins with folic acid is important to prevent birth defects. The gastrointestinal tract and sensory organs also grow. The bone begins to replace cartilage.

Your baby’s head fits the rest of his body at this stage. At about six weeks, your baby’s heart rate is usually detectable. By the end of the second month, your baby is about 1 inch long and weighs about 1/30 ounces.

Month 3 (weeks 9 through 12)

The baby’s arms, hands, and fingers are fully formed. At this point, your baby will begin to explore a bit by doing things like opening and closing his fists and mouth. Nails start to grow, and teeth form under the gums. The baby’s reproductive organs also develop, but it is difficult to determine the sex of the baby.

The baby’s circulatory and urinary systems also work, and the liver produces bile. Because the baby’s most important growth has occurred, the chance of miscarriage after three months is significantly reduced. By the end of the third month, the baby is about 4 inches long and weighs about 1 ounce.

Second trimester

This middle part of pregnancy is often considered the best part of pregnancy. By this time, any morning sickness is probably gone. During this month, the baby will begin to develop facial features.
The small fetus, which now has a unique fingerprint, settles in its desired location, and its heart pumps 25 liters of blood day and night.

After a few weeks, the skeleton becomes denser and turns from rubber cartilage to bone. The ability to hear increases, and the fetus is likelier to feel the baby shaking and kicking.

Month 4 (weeks 13 through 16)

Welcome to the second trimester. The baby’s heartbeat can be heard through a device called a Doppler. Eyelids, eyebrows, eyelashes, nails, and hair are formed. Teeth and bones become denser. Baby’s arms and legs are now moving, and kidneys are also starting to produce urine. The nervous system begins to work. The genitals are now fully developed, and the sex of the baby can be identified.

By the end of the fourth month, your baby is about 6 inches long and weighs about 4 ounces.

Month 5 (weeks 17 through 20)

At this point, you may feel your baby spinning. The hair on the baby’s head begins to grow. This hair protects your baby and is usually shed at the end of the first week of life.

The baby’s skin is covered with a white coating called vernix caseosa. This “cheese” protects the skin from prolonged exposure to amniotic fluid. This cover is shed just before birth. The fetus has an hour of sleep and wakefulness; depending on its movement, you will know when it is awake or asleep.

The fetus has all its lifelong eggs inside the ovary if it is a girl. By the end of the fifth month, the baby is about 10 inches long and weighs from 1/2 to 1 pound.

Month 6 (weeks 21 through 24)

If you could look at your baby right now, you would see that your baby’s skin is reddish and wrinkled, and the veins are visible through the baby’s clear skin. At this point, the eyelids begin to shrink, and the fetus can open its eyes. The baby’s lungs are also formed but not fully functional.

Brain growth is also rapid at this stage. The child responds to sounds by moving or increasing the pulse. By the end of the sixth month, the baby is about 12 inches long and weighs about 2 pounds.

Month 7 (weeks 25 through 28)

Your baby will continue to mature and develop body fat stores. At this stage, the child’s hearing is fully developed. The child constantly changes position and responds to sound, pain, and light stimuli. Amniotic fluid begins to shrink. The baby’s lungs make a surfactant that helps them expand at birth. By the end of the seventh month, your baby is about 14 inches long and weighs 2 to 4 pounds.

Third trimester

In the third trimester of pregnancy, the fetus’s skin absorbs fatter, removes wrinkles, and becomes smooth skin. Toenails grow, and billions of brain neurons are formed. This is the last part of pregnancy.

You may be tempted to start counting down to your due date and hope it arrives earlier, but each week from this final stage of development will help your baby prepare for birth. During the third trimester, your baby will gain weight quickly.

Month 8 (weeks 29 through 32)

Your baby will continue to mature and develop body fat stores. You may find that your baby kicks more. Baby’s brain is developing rapidly at this time, and your baby can see and hear. Most internal systems are well-developed, but the lungs may be immature.

The baby’s bones became harder, the skull a little softer, and made up of four bones to make labor easier. Your baby can taste sweet and sour by taste buds at this point, and the baby gains weight faster. The baby is about 18 inches long and weighs 5 pounds.

Month 9 (weeks 33 through 36)

Your baby continues to grow and mature. The lungs grow fully. Your baby’s movements increase. The child can turn his head, understand his surroundings, and respond to sounds, light, and contact.

The baby is getting ready to be born. You may feel more movement. But the baby changes position to prepare for delivery. The baby goes down to your pelvis to be ready for delivery. Your baby is about 17 to 19 inches tall and weighs 5 to 6 pounds.

Month 10 (Weeks 37 through 40)

After the end of the ninth month, the pregnant mother is ready to give birth. You may feel the baby is moving less because of the tight space. Ideally, the baby will sink into your womb. The child is ready to meet the world at this point. Your baby is about 18 to 20 inches tall and weighs about 7 pounds.

Babies are rarely born on their due date. The due date is only a date calculated based on the average. Most women give birth within two weeks before or two weeks after the due date. Sometimes there are medical reasons to intervene and start labor earlier.

The bottom line

Pregnancy is a very sensitive and important time. Know what happens to the fetus each month and what you do best for the fetus to have healthier babies and minimize your risk of pregnancy. The mother’s stress and anxiety are transmitted to the fetus and cause her harm. So be more careful in the 9th month of pregnancy.

Arjang Naim, MD, is with you throughout your pregnancy, always answering your questions and examining the fetus during the check-ups to care for you and your fetus.

Additional questions

What are the stages of fetal development?

Between conception and delivery, many precise steps must be taken. The three stages of fetal development include:

Germinal
Embryonic
Fetal

What is the first organ that develops in the fetus?

The first organ system to develop during organogenesis is the cardiovascular system. The heart has developed its four chambers by four weeks of development, while the sixth week involves the separation of the cardiac outflow tract and the descent of the heart (and lungs) into the thorax.

What are the stages of a blastocyst?

First, the zygote becomes a solid ball of cells. It then turns into a hollow ball of cells called a blastocyst. Inside the uterus, the blastocyst implants in the uterine wall, where it develops into an embryo attached to the placenta and surrounded by a fluid-filled membrane.

What is blastocyst vs. zygote?

The zygote contains all the genetic information (DNA) needed to become a child. Half of the DNA comes from the mother’s egg and half from the father’s sperm. The zygote spends the next few days traveling down the fallopian tube. During this time, it divides and forms a ball of cells called a blastocyst.