How does a fetus develop inside the womb

The placenta is a round, flat organ that transfers nutrients from the mother to the baby, and transfers wastes from the baby. The fifth week of pregnancy, or the third week after conception, marks the beginning of the embryonic period. At 32 weeks, many babies weigh about 4 pounds, and have movements that the mother can feel. Further cellular division is accompanied by the formation of a small cavity between the cells.

A primitive face will take form with large dark circles for eyes. This is when the baby’s brain, spinal cord, heart and other organs begin to form. Your doctor may ask you to make notes about the baby’s movements and discuss breastfeeding and other options along with scheduling visits every two weeks until you deliver the baby. This stage is called a blastocyst. The mouth, lower jaw, and throat are developing.
The embryo is now made of three layers. Some women begin to leak a yellowish fluid from their breasts around this time; this is normal and the fluid is termed colostrum and indicates the breasts are primed to start producing milk for the newborn baby. Up to this point there is no growth in the overall size of the embryo, as it is confined within a glycoprotein shell, known as the zona pellucida. Blood cells are taking shape, and circulation will begin. The top layer — the ectoderm — will give rise to your baby’s outermost layer of skin, central and peripheral nervous systems, eyes, inner ears, and many connective tissues.

The beginning of fertilization

At 36 weeks the baby is about ready to be delivered and has reached an average length of 18.5 inches from head to heel length and weighs about 6 pounds. Instead, each division produces successively smaller cells. The tiny “heart” tube will beat 65 times a minute by the end of the fourth week. Your baby’s heart and a primitive circulatory system will form in the middle layer of cells — the mesoderm. However, baby weight and length are quite variable and are influenced by the baby’s parental genetics, the baby’s sex, and many other factors.

The blastocyst reaches the uterus at roughly the fifth day after fertilization. By the end of the first month, your baby is about 1/4 inch long – smaller than a grain of rice.ur baby’s facial features continue to develop. This layer of cells will also serve as the foundation for your baby’s bones, muscles, kidneys and much of the reproductive system. During this time, the baby has begun to rotate itself into the delivery position of head first into the pelvis. It is here that lysis of the zona pellucida occurs.

Each ear begins as a little fold of skin at the side of the head. The inner layer of cells — the endoderm — will become a simple tube lined with mucous membranes. At 37 weeks, the baby has completed development of all organ systems to a level that should allow it to survive and continue its growth outside the uterus without any close hospital monitoring that is usually done with premature babies; consequently, the pregnancy is considered “at term” at 37 weeks and beyond. This process is analogous to zona hatching, a term that refers to the emergence of the blastocyst from the zona pellucida, when incubated in vitro. Tiny buds that eventually grow into arms and legs are forming.

Your baby’s lungs, intestines and bladder will develop here. Delivery, due or birth date is calculated by estimating a 40 weeks delivery date, calculated after the first day of the mother’s last period. This allows the trophectoderm cells of the blastocyst to come into contact with, and adhere to, the endometrial cells of the uterus. Fingers, toes and eyes are also forming. By the end of this week, your baby is likely about the size of the tip of a pen.

This is an estimated date; the normal vaginal delivery birth can occur easily between 38 and about 42 weeks and is considered an early or late term pregnancy. The trophectoderm will eventually give rise to extra-embryonic structures, such as the placenta and the membranes. The neural tube (brain, spinal cord and other neural tissue of the central nervous system) is well formed. Growth is rapid this week. However, most babies are delivered before 42 weeks.

The embryo becomes embedded in the endometrium in a process called implantation. The digestive tract and sensory organs begin to develop. Just four weeks after conception, the neural tube along your baby’s back is closing and your baby’s heart is pumping blood. Depending on various circumstances and complications, the doctor may need to induce labor and delivery in some women, while others may require a surgical delivery (Caesarean section or C-section). For most people, especially first-time parents, birth of an infant is a life-changing event! In most successful pregnancies, the embryo implants 8 to 10 days after ovulation.

Bone starts to replace cartilage. Basic facial features will begin to appear, including passageways that will make up the inner ears and arches that will contribute to the jaw. The embryo, the extra-embryonic membranes, and the placenta are collectively referred to as a conceptus, or the “products of conception”. The head is large in proportion to the rest of the baby’s body. Your baby’s body begins to take on a C-shaped curvature.

First sign of pregnancy

Rapid growth occurs and the embryo’s main features begin to take form. By the end of the second month, your baby is about 1 inch long and weighs about 1/30 of an ounce. Small buds will soon become arms and legs. This process is called differentiation, which produces the varied cell types (such as blood cells, kidney cells, and nerve cells). A spontaneous abortion, or miscarriage, in the first trimester of pregnancy is usually due to major genetic mistakes or abnormalities in the developing embryo. At about 6 weeks, your baby’s heart beat can usually be detected.

Seven weeks into your pregnancy, or five weeks after conception, your baby’s brain and face are rapidly developing. Gestational age is the time that has passed since the onset of the last menstruation, which generally or as standard occurs 2 weeks before the actual fertilization. After the 8th week, your baby is called a fetus instead of an embryo. Tiny nostrils become visible, and the eye lenses begin to form. Embryonic age, in contrast measures the actual age of the embryo or fetus from the time of fertilization.
Your baby’s arms, hands, fingers, feet, and toes are fully formed. The arm buds that sprouted last week now take on the shape of paddles. Nevertheless, menstruation has historically been the only means of estimating embryonal/fetal age, and is still the presumed measure if not else specified. Your baby can open and close its fists and mouth. By the end of this week, your baby might be a little bigger than the top of a pencil eraser.

However, the actual duration between last menstruation and fertilization may in fact differ from the standard 2 weeks by several days. Fingernails and toenails are beginning to develop and the external ears are formed. Eight weeks into your pregnancy, or six weeks after conception, your baby’s arms and legs are growing longer, and fingers have begun to form. Thus, the first week of embryonic age is already week three counting with gestational age. The beginnings of teeth are forming.

The shell-shaped parts of your baby’s ears also are forming, and your baby’s eyes are visible. Furthermore, the number of the week is one more than the actual age of the embryo/fetus. Your baby’s reproductive organs also develop, but the baby’s gender is difficult to distinguish on ultrasound. The upper lip and nose have formed. For example, the embryo is 0 whole weeks old during the 1st week after fertilization.

By the end of the third month, your baby is fully formed. The trunk of your baby’s body is beginning to straighten. The following table summarizes the various expression systems during week number x of gestation. All the organs and extremities are present and will continue to mature in order to become functional. By the end of this week, your baby might be about 1/2 inch (11 to 14 millimeters) long.


The circulatory and urinary systems are working and the liver produces bile. In the ninth week of pregnancy, or seven weeks after conception, your baby’s arms grow, develop bones and bend at the elbows. At the end of the third month, your baby is about 4 inches long and weighs about 1 ounce. Toes form, and your baby’s eyelids and ears continue developing. Since your baby’s most critical development has taken place, your chance of miscarriage drops considerably after three months.

Leave a Reply

Your email address will not be published. Required fields are marked *