Because the brain has to grow.
In week 9 the fetus begins to develop fingernails and body hair. By week 13 fine hairs begin to grow on the head.
In a fetus, the head is relatively larger compared to the body in the early stages of development. As the fetus grows, the body catches up in size. By the time of birth, the head and body proportions are more balanced.
During the third trimester, a developing fetus undergoes significant growth and maturation. The fetus gains weight rapidly, accumulating fat, which helps regulate body temperature after birth. Additionally, major organs and systems continue to develop and become more functional, particularly the lungs and brain. By the end of this trimester, the fetus is typically positioned head-down in preparation for birth.
At 7 months of gestation in a horse, the fetus is approximately 28 inches in length and can weigh around 45-50 pounds. It is covered in hair and its physical features like the head, limbs, and body are well-defined. The fetus is fully formed but still needs more time in the womb to further develop and mature before birth.
At 13 weeks gestation, a fetus typically measures around 2.9 inches in CRL, which is the length from the top of the head to the bottom of the spine. At this stage, the fetus has developed all major organs and body systems, and its limbs are more defined. The fetus can make movements, although the mother may not feel them yet. The skin is thin and transparent, and the fetus is starting to develop fingerprints.
The condition that causes a fetus not to develop a head is called anencephaly. It is a neural tube defect that occurs when the upper part of the neural tube fails to close during early embryonic development, resulting in the absence of significant portions of the brain and skull. Anencephaly is a serious condition, and affected infants typically do not survive long after birth.
Because
The biggest part of the fetus is the head/brain..
It isn't. The rest of the body is small.
Head to toe of the fetus is parallel to the ground Head to toe of the fetus is parallel to the ground
Microcephaly is an extremely rare condition in which the fetus's head circumference is lower then one percentile.
Between a two-month fetus and an infant, the parts of the body that appear to grow the most are the head, limbs, and internal organs. The head grows rapidly in proportion to the rest of the body during fetal development, while the limbs elongate and become more defined. Internal organs also undergo significant growth and maturation during this period to support the developing body.