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During continued fetal development, the early body systems, and structures that were established in the embryonic stage continue to develop. Sex organs begin to appear during the third month of gestation. The fetus continues to grow in both weight and length, although the majority of the physical growth occurs in the last weeks of pregnancy.
Fertilization was not understood in antiquity. Hippocrates believed that the embryo was the product of male semen and a female factor. But Aristotle held that only male semen gave rise to an embryo, while the female only provided a place for the embryo to develop, [5] a concept he acquired from the preformationist Pythagoras.
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 ...
Adequate nutrition is needed for a healthy fetus. Mothers who gain less than 20 pounds during pregnancy are at increased risk for having a preterm or low birth weight infant. [51] Iron and iodine are especially important during prenatal development. Mothers who are deficient in iron are at risk for having a preterm or low birth weight infant. [52]
Development of the human body is the process of growth to maturity. The process begins with fertilization , where an egg released from the ovary of a female is penetrated by a sperm cell from a male.
The step lengthens as the pregnancy progresses, due to weight gain and changes in posture. On average, a woman's foot can grow by a half size or more during pregnancy. In addition, the increased body weight of pregnancy, fluid retention, and weight gain lowers the arches of the foot, further adding to the foot's length and width.
If the testicles remain too close to the body, it is likely that the increase in temperature will harm the spermatozoa formation, making conception more difficult. This is why the testes are carried in an external scrotum rather than within the abdomen; they normally remain slightly cooler than body temperature, facilitating sperm production.
44% will have a conception ending in a live birth within one year 64% will have a conception ending in a live birth within four years [ 13 ] According to a study done on a sample of 782 healthy European couples ages 19–39, fertility starts declining after age 27 and drops at a somewhat greater rate after age 35.