Search results
Results From The WOW.Com Content Network
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.
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.
A human fetus, attached to placenta, at three months gestational age. In humans, the fetal stage starts nine weeks after fertilization. [7] At this time the fetus is typically about 30 millimetres (1 + 1 ⁄ 4 in) in length from crown to rump, and weighs about 8 grams. [7] The head makes up nearly half of the size of the fetus. [8]
Human embryonic development covers the first eight weeks of development, which have 23 stages, called Carnegie stages. At the beginning of the ninth week, the embryo is termed a fetus (spelled "foetus" in British English). In comparison to the embryo, the fetus has more recognizable external features and a more complete set of developing organs.
A newly developing human is typically referred to as an embryo until the ninth week after conception, when it is then referred to as a fetus. In other multicellular organisms, the word "embryo" can be used more broadly to any early developmental or life cycle stage prior to birth or hatching.
At week 11, the fetus can open its mouth and suck its fingers; at week 12, it begins to swallow amniotic fluid. [10] In addition to sideward bendings of the head, complex and generalized movements occur at the beginning of the fetal stage, with movements and startles that involve the whole body. [11]
A fetus born prior to the 37th week of gestation is considered to be preterm. A preterm baby is likely to be premature and consequently faces increased risk of morbidity and mortality. An estimated due date is given by Naegele's rule. According to the WHO, a preterm birth is defined as "babies born alive before 37 weeks of pregnancy are completed."
Adapted to the weight of the fetus, this corresponds to 115 mL/min/kg at 20 weeks and 64 mL/min/kg at 40 weeks. [18] It corresponds to 17% of the combined cardiac output of the fetus at 10 weeks, and 33% at 20 weeks of gestation. [18] Endothelin and prostanoids cause vasoconstriction in placental arteries, while nitric oxide causes vasodilation ...