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| 16.37 | Human birth: day 61 to 266/300 fetus to birth | |
| By the beginning of the third month (Day 61 +) the young fetus clearly resembles a human being, although the head is disproportionately large. | ||
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| The previous protrusion of much of the intestine into the umbilical cord is reduced through the return of its loops into the abdomen. The ears rise to eye level and the eyelids fuse shut. Nails begin forming; ossification (bone-forming) centres appear in most of the future bones; and the sex of external genitalia becomes recognizable. | ||
At four months individual differences between the faces of fetuses become distinguishable. The face is broad but the eyes are now less widely separated. The umbilical cord attaches higher on the abdominal wall; this location is above an expanding region between the cord and the pubis (front bones of the pelvis) that scarcely existed previously. |
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| At five months downy hairs (lanugo) cover the body, and some head hairs appear. The skin is less transparent. Fetal movements ("quickening") are felt by the mother. At six months eyebrows and eyelashes are clearly present. The body is lean, but its proportions have improved. The skin is wrinkled. | ||
| At seven months the fetus resembles a dried-up old person. Its reddish, wrinkled skin is smeared with a greasy substance (vernix caseosa). The eyelids reopen. | ||
At eight months fat is depositing beneath the skin. The testes begin to invade the scrotum. At nine months the dull redness of the skin fades and wrinkles smooth out. The body and limbs become better rounded. |
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At full term (38 weeks) the body is plump and proportions are improved, although the head is large and the lower limbs are still slightly shorter than the upper limbs. The skin has lost its coat of lanugo hair, but it is still smeared with vernix caseosa. Nails project beyond the finger tips and to the tips of toes. The umbilical cord now attaches to the centre of the abdomen. |
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| The testes of males are usually in the scrotum; the greater lips of the female external genitalia, which previously gaped, are now in contact. Cranial bones meet except at some angular junctions, or "soft spots." | ||
| The average time of delivery is 280 days from the beginning of the last menstrual period, whereas the duration of pregnancy (age of the baby) is about 266 days (38 weeks). Pregnancy may extend to 300 days, or even more, in which case the baby tends to be heavier. Premature babies born under 27 weeks of age rarely survive, whereas those more than 30 weeks old usually do survive. | ||
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