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The first ten weeks of gestational age is the period of embryogenesis and together with the first three weeks of prenatal development make up the first trimester of pregnancy. From the 10th week of gestation (8th week of development), the developing embryo is called a fetus.
Embryonic age: Week nr 4. 3 weeks old. 22–28 days from fertilization. The embryo measures 4 mm (1 ⁄ 8 in) in length and begins to curve into a C shape. The heart bulges, further develops, and begins to beat in a regular rhythm. Septum primum appears. [1] Pharyngeal arches, grooves which will form structures of the face and neck, form.
The postpartum period also referred to as the puerperium, is the postnatal period that begins immediately after delivery and extends for about six weeks. [60] During this period, the mother's body begins the return to pre-pregnancy conditions that includes changes in hormone levels and uterus size. [60]
Human sexual reproduction, to produce offspring, begins with fertilization. Successful reproduction typically involves sexual intercourse between a healthy, sexually mature and fertile male and female. [1] During sexual intercourse, sperm cells are ejaculated into the vagina through the penis, resulting in fertilization of an ovum to form a ...
Development before birth, or prenatal development (from Latin natalis 'relating to birth') is the process in which a zygote, and later an embryo, and then a fetus develops during gestation. Prenatal development starts with fertilization and the formation of the zygote , the first stage in embryonic development which continues in fetal ...
When eight blastomeres have formed, they start to compact. [6] They begin to develop gap junctions, enabling them to develop in an integrated way and co-ordinate their response to physiological signals and environmental cues. [7] When the cells number around sixteen, the solid sphere of cells within the zona pellucida is referred to as a morula ...
The WHO defines the perinatal period as "The perinatal period commences at 22 completed weeks (154 days) of gestation and ends seven completed days after birth." [26] Perinatal mortality is the death of fetuses or neonates during the perinatal period. A 2013 study found that "While only a small proportion of births occur before 24 completed ...
This can happen up to about 50–73 hours after birth. Once full lactation begins, the woman's breasts swell significantly and can feel achy, lumpy and heavy (which is referred to as engorgement). Her breasts may increase in size again by an additional 1 or 2 cup sizes, but individual breast size may vary depending on how much the infant nurses ...