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Mammals during pregnancy can have one or more gestations at the same time, for example in a multiple birth. [2] The time interval of a gestation is called the gestation period. In obstetrics, gestational age refers to the time since the onset of the last menses, which on average is fertilization age plus two weeks. [3]
The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days. [1] During this stage, the zygote divides in a process called cleavage.
Gestational age: 12 weeks and 0 days until 15 weeks and 6 days old. Embryonic age: 10 weeks and 0 days until 13 weeks and 6 days old. The fetus reaches a length of about 15 cm (6 in). A fine hair called lanugo develops on the head. Fetal skin is almost transparent. More muscle tissue and bones have developed, and the bones become harder.
For example, if there is a gestational age based on the beginning of the last menstrual period of 9.0 weeks, and a first-trimester obstetric ultrasonography gives an estimated gestational age of 10.0 weeks (with a 2 SD variability of ±8% of the estimate, thereby giving a variability of ±0.8 weeks), the difference of 1.0 weeks between the ...
Gestation period is about 266 days in humans. While in the uterus, the baby first endures a very brief zygote stage, then the embryonic stage, which is marked by the development of major organs and lasts for approximately eight weeks, then the fetal stage, which revolves around the development of bone cells while the fetus continues to grow in ...
Pregnancy is the time during which one or more offspring develops inside a woman's uterus (womb). [4] [13] A multiple pregnancy involves more than one offspring, such as with twins. [14] Pregnancy usually occurs by sexual intercourse, but can also occur through assisted reproductive technology procedures. [6]
About 80% of childbirths occur between 37 and 41 weeks of gestational age, with a somewhat more narrow span when based on first trimester ultrasound. [11] Given that these gestation lengths are only estimates of an average, it is helpful to consider gestation time as a range of dates rather than as a single "due date".
In human pregnancy, prenatal development is also called antenatal development. The development of the human embryo follows fertilization, and continues as fetal development. By the end of the tenth week of gestational age, the embryo has acquired its basic form and is referred to as a fetus. The next period is that of fetal development where ...