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kotesh
First trimester
Traditionally, doctors have measured pregnancy from a number of convenient points, including the day of last menstruation, ovulation, fertilization, implantation and chemical detection. In medicine, pregnancy is often defined as beginning when the developing embryo becomes implanted into the endometrial lining of a woman's uterus. In some cases where complications may have arisen, the fertilized egg might implant itself in the fallopian tubes, the cervix, the ovary or in the abdomen causing an ectopic pregnancy. In the case of an ectopic pregnancy there is no way for the pregnancy to progress normally. If left untreated, it can cause harm and possibly death for the mother when a rupture occurs. Sometimes it will go away on its own but otherwise a surgical procedure or medicine is given to remove the tubal pregnancy since there is no way of the pregnancy being able to continue safely.[28] Most pregnant women do not have any specific signs or symptoms of implantation, although it is not uncommon to experience minimal bleeding at implantation. Some women will also experience cramping during their first trimester. This is usually of no concern unless there is spotting or bleeding as well. After implantation the uterine endometrium is called the decidua. The placenta, which is formed partly from the decidua and partly from outer layers of the embryo, connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. The umbilical cord is the connecting cord from the embryo or fetus to the placenta. The developing embryo undergoes tremendous growth and changes during the process of fetal development.
Morning sickness occurs in about seventy percent of all pregnant women and typically improves after the first trimester.[29][dead link] Although described as "morning sickness", women can experience this nausea during afternoon, evening, and throughout the entire day.
In the first 12 weeks of pregnancy, the nipples and areolas darken due to a temporary increase in hormones.[30]
The first 12 weeks of pregnancy are considered to make up the first trimester. The first two weeks from the first trimester are calculated as the first two weeks of pregnancy even though the pregnancy does not actually exist. These two weeks are the two weeks before conception and include the woman's last period.
The third week is the week in which fertilization occurs and the 4th week is the period when implantationuterus and burrows into its wall which provides it with the nutrients it needs. At this point, the zygote becomes a blastocyst and the placenta starts to form. Moreover, most of the pregnancy tests may detect a pregnancy beginning with this week. takes place. In the 4th week, the fecundated egg reaches the
The 5th week marks the start of the embryonic period. This is when the baby's brain, spinal cord, heart and other organs begin to form.[31] At this point the embryo is made up of three layers, of which the top one (called the ectoderm) will give rise to the baby's outermost layer of skin, central and peripheral nervous systems, eyes, inner ear, and many connective tissues.[31] The heart and the beginning of the circulatory system as well as the bones, muscles and kidneys are made up from the mesoderm (the middle layer). The inner layer of the embryo will serve as the starting point for the development of the baby's lungs, intestine and bladder. This layer is referred to as the endoderm. A baby at 5 weeks is normally between 1⁄16 and 1⁄8 inch (1.6 and 3.2 mm) in length.
In the 6th week, the baby will be developing basic facial features and its arms and legs start to grow. At this point, the embryo is usually no longer than 1⁄6 to 1⁄4 inch (4.2 to 6.3 mm). In the following week, the brain, face and arms and legs quickly develop. In the 8th week, the baby starts moving and in the next 3 weeks, the baby's toes, neck and genitals develop as well. According to the American Pregnancy Association, by the end of the first trimester, the fetus will be about 3 inches (76 mm) long and will weigh approximately 1 ounce (28 g).[32]
