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Day 1-5 of menses cycle
Menstrual phase- functional layer of the endometrial lining is sloughing off from the uterine wall. This is the stage where the woman is bleeding and still has her period. All of the detached tissue and blood is going through the vagina. By day 5, her ovarian follicles are beggining to produce more estrogen to stimulate the re-growth of the functional layer. -
Day 6-14 of menses cycle
Proliferative phase- from the stimulated estrogen levels, the basal layer of the endometrium regenerates the functional layer. Glans begine to form in the functional layer and the endometrial blood supply increases. The endometrium becomes velvety thick and vascularized. Finally, ovulation occurs in the ovary at the end of this stage as a response to the increase of LH in the blood. -
Day 15-28
The is the secretory phase of the menstrual cycle. There are rising levels of progesterone that increase the blood supply to the endometrium. Progesterone also causes the endometrial glands to increase in size and begin to secrete nutrients into the uterine cavity. These nutrients sustain the developing zygote until it's implated in the uterus. Fertilization is occuring and the zygote produces hormones similar to LH, causing the corpus luteum to continue producing it's hormones. -
Right after conception
The zygote is making its way down the uterine tube and begins to go through repeated mitotic cell division. The zygote is going through 'cleavage' producing daughter cells. Cleavage provides for a large number of cells to serve as building blocks for constructing the embryo. On the 17th day, the developing embryo becomes a morula (a ball of 16 cells). The placenta starts to form as a result of conception. -
4 Weeks
At this point the mother can take an at-home pregnancy test and she is able to know that she is pregnant. The embryo is developing structures that will make up the head and neck. Heart and blood vessels start to develop along with primary organs of the body such as the liver, stomach, and the lungs. The embryo is about the size of a poppyseed at this point. -
8 weeks
The head is nearly as large as the body and all major brain regions are present. Limbs are present, except the fingers and toes are webbed but by the end of this period, they begin to seperate. Eyelids and ears are starting to form as well. Bones have begun to form. The embryo is approximately 30 mm and weighs 1 gram. The fetus is about the size of a raspberry. -
12 Weeks
The fetus is about 2 inches at this point. The doctor should be able to hear the heartbeat and the sex organs start to become clear. Bone formation is accelerating. The fetus is about the size of a plum. -
16 Weeks
The fetus now measures about 4.3 to 4.6 inches and weighs about 3.5 ounces. The fetus can blink and the heart and blood vessels are fully formed. The fingers and toes have fingerprints. The eyes and ears take shape and position, the face looks human and the body is starting to pick up in growth compared to the head. The kidneys are starting to attain their structure. The fetus is about the size of an avocado. -
20 Weeks
The baby weighs about 10 ounces and is a little more than 6 inches long. The womans uterus should be at the level of her belly button. At this point in development, the baby will start to move around. This is called "quickening". The Vernix caseosa, which is the fatty secretion of the sebaceous glands, cover the body and silklike hair covers the skin, called lanugo. The baby is about the size of a banana. -
24 Weeks
At this time the woman usually has her first ultrasound. During this ultrasound, the doctor will make sure that the placenta is healthy and attached normally and that the baby is growing properly. The baby's heartbeat and movement of its body, arms, and legs are also visible on the ultrasound. Substantial weight increase in the baby. Mylenation of the spinal cord begins and the eyes are open. The baby is about the size of a cantelope. -
28 Weeks
The baby weighs about 2 pounds 6 ounces. If the baby was delivered prematurely, it would most likely survive. Skin is wrinkled and red. The fingernails and toe nails are present. The baby's body is lean and well-proportioned while the bone marrow becomes the sole site of blood cell formation. If male, the testes enter the scrotum. The baby is about the size of an eggplant. -
32 Weeks
At this point, the baby weighs almost 4 pounds. The skin has fewer wrinkles and a layer of fat is deposited underneath the skin. Between now and delivery the baby will gain up to half its birth weight. The baby is about the size of a squash. -
36 Weeks
The brain has been developing rapidly, the lungs are almost fully developed, and the head is usually positioned down in the pelvis. The baby is about the size of a honeydew. -
40 Weeks. Delivery!
The 40th week marks the delivery of the baby! And a long and pretty painful day of labor. The baby is usually the size of a jackfruit.
