The duration of pregnancy is normally 38-40 weeks and is divided into three periods
referred to as trimesters—three distinct stages/periods of foetal development.
First trimester
Foetal development begins in the first trimester with the fertilization of an ovum by a
sperm. The newly formed ovum or zygote begins as a single cell and then divides to
become many cells after fertilization. Within two weeks the zygote embeds itself in
the uterus a process known as implantation. Cell division continues and the zygote
becomes an embryo. An embryo is the developing infant from 2-8 weeks. The
embryo at 8 weeks has a complete central nervous system, a beating heart,
digestive system, well defined fingers and toes and the beginning of facial
features. This is a critical period of development and any injury to the embryo caused
by nutritional deficiencies, medication, illegal drugs, radiation, trauma or other factors
can alter or arrest the specific phase of growth and development in progress.
Some defects such as cleft palate, missing limbs, abnormal development of the
neural tube or its failure to close completely can produce major defects in the
central nervous system causing serous disabilities and infant death. Spina bifida (It
is associated with folate deficiency) is one of the most common types of neural
tube defects a disorder characterized by incomplete closure of the spinal cord
and its encasement. The membranes covering the spinal cord often protrude as a
sac, which may rupture and lead to meningitis a life threatening inflammation of
the membranes. Spina bifida is accompanied by a varying degree of paralysis
depending on the extent of the spinal cord damage. It is associated with folate
deficiency. The first trimester is therefore a critical period of intrauterine development
and a woman should therefore be careful to avoid substances that can harm the
developing embryo.
spina bifida
Second trimester
During this trimester, the foetus weighs about 30 grams. Arms, hands, fingers, legs,
feet and toes are fully formed. The foetus has ears and is beginning to form tooth
sockets in its jawbone. The developing organs continue to grow and mature and the
physician can detect a heartbeat. Most bones are distinct throughout the body and the
foetus begins to look like an infant. It may suck its thumb and kick strongly to be felt
by the mother.
Third trimester
At the beginning of this trimester, a foetus weighs approximately 1 kg. Mineral and
fat stores normally accumulate during this last months. By 9 months, the typical
foetus weighs about 3-3.5 kg and is about 50 cm in length.
Titany answered the question on November 8, 2021 at 06:45
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