From the first moment you find out you are pregnant, you are often excited, cannot believe it, and realize you are just about to experience a wonderful adventure. It may be that you are scared at the thought of giving birth and might wonder how you will be able to do it. You realize that your body is already changing, even though no one else can see it, and are likely feeling tired.
The different stages of pregnancy are measured by the fetus? gestational age.
Your pregnancy began when the fertilized egg implanted into your uterus. Approximately 2 weeks after your period, the unfertilized egg was at its most mature stage and released from one of your two ovaries during ovulation. When it was released, it began traveling down the fallopian tube, heading toward the uterus.
During this time, if the egg makes contact with the sperm from the potential father, it combines to form a single cell during the fertilization process. Pregnancy is often the result of unprotected vaginal intercourse that occurs up to six days prior to your ovulation.
As a fertile eggs egg continues to move down the fallopian tube, it will divide into more cells until reaching the uterus, approximately 4 days after it has been fertilized. The dividing cells begin to form a ball, floating freely in your uterus for up to three days. It is during this time the pregnancy begins, as this ball of cells attach to the interior lining of your uterus during implantation. Pregnancy is not an automatic occurrence, as up to 50 percent of all fertilized eggs can pass through the uterus without implanting in the walls.
By the second month of your pregnancy, the little ball of cells has now developed into an embryo at approximately the sixth week during the embryonic stage, lasting approximately 5 weeks. It is during this stage that the embryo?s major internal organs begin to develop. Even though your body is changing, the embryo is only approximately 5 millimeters long, or about 1⁄5 of an inch.
At this stage, the basic heart rhythms begin to beat and the circulatory system starts to develop. In addition, tiny buds that will later grow into the legs and arms begin to develop, along with a budding tail. During this stage, the umbilical cord starts to develop.
By the seventh and eighth week, the heart has now formed, and the embryo?s arms are now bending at elbows. Webbed toes and fingers develop along with external ears, eyelids, eyes, upper lip and liver. At this stage, the sex organs that have remained the same up to this point ? neither male nor female ? become triggered by genes. It is at this time the fetus begins developing ovaries in a female or testes for a male.
A Developing Fetus
By the ninth week the tail has disappeared in the toes and fingers have become much longer. The embryo has finally developed into a fetus. However, it still measures less than an inch and a half (up to 40 millimeters) in length. The umbilical cord is now connected from the placenta to the fetus?s abdomen. The interior wall of the uterus holds the placenta in place, allowing it to absorb nutrients from the mother?s bloodstream to carry oxygen and nutrients to the fetus and to take waste products away.
During this stage, the fingernails and skin begin to grow, and bones become hardened. The kidneys begin making urine, eyelids are fusing together, and sweat glands start to develop. In addition, hormones in the fetus begin to develop external sex organs.
By the 14th week, male fetuses begin developing a prostate gland, while ovaries and females move from the abdomen into the pelvis area. The roof of the fetus?s mouth begins to form and hair starts to grow. By the 15th week, eggs by the hundreds of thousands are forming in the female fetus? ovaries.
By the 20th week, a fine downy hair (lanugo) covers the body of the fetus, in addition to a greasy material (vertex caseosa) that provides protection to the skin. In females, the uterus is formed. By the 22nd week, bone marrow begins creating blood cells, and taste buds start to form. At this stage, eyelashes and eyebrows have developed.
The Final Stage
By the 26th week, the fetus has developed more fat, which will remain until delivery. By the 28th week, the eyelids are no longer fused together. At week 30, the male fetus?s testes have started to descend into the scrotum, which will take until the last week of pregnancy to complete. In week 31, the lanugo (downy hair) begins to fall off.
During the last month of pregnancy, the fetus? eyes have developed significantly. The pupils can now constrict and dilate whenever exposed to a light source. The fetus has now become significantly fatter and the skin no longer has a wrinkly appearance.
At around the 39th or 40th week of pregnancy, most women give birth. On average, a typical newborn will weigh between seven and eight pounds and measure 18 to 22 inches in length when the legs are extended. After delivery, the placenta and other pregnancy tissues are discharged from the mother?s body during the afterbirth stage.
Optometrists and gynecologist typically divide the stages of pregnancy into three trimesters. The stages begin just before conception and end with delivery of your newborn.