Knowing How Your Fetus Develops In The 1st Trimester Of Pregnancy

Knowing How Your Fetus Develops In The 1st Trimester Of Pregnancy

17 Oct 2022 | 3 min Read

Seema Bhatia

Author | 29 Articles

The first trimester consists of the first 12 weeks of pregnancy, where the body starts preparing for the pregnancy followed by fertilization and then fetal growth.

In the first two weeks of pregnancy, the body starts preparing for conception.

In the third week, the fertilization process takes place, where the egg unites with the sperm to form a zygote.  The zygote then travels from the fallopian tube to the uterus and simultaneously starts dividing into cells forming a cluster.

In the fourth week, the ball of cells (blastocyst) attaches to the uterus by the process of implantation.

The fifth week is marked by the increase in the HCG hormone levels that leads to no further release of eggs and supports the growth of the placenta. At this stage, your embryo is made up of three layers of cells that include ectoderm (top layer), mesoderm (middle layer), and endoderm (inner layer).

The baby’s intestine and lungs form from the inner layer. The baby’s bones, kidneys, ligaments, and most of the reproductive system form from the middle layer. Lastly, the top layer becomes a foundation of the eyes, skin, inner ears, central nervous system, and peripheral nervous system.

In the sixth week, the growth becomes rapid. The neural tube closes. Baby’s heart and other organs start forming this week. Necessary structures for ears and eyes start forming along with small buds that develop into arms in the coming weeks.

In the seventh week, the baby’s brain and facial structures grow along with the sprouting of the arm buds into the form of paddles. The lower limb buds and the depression giving rise to nostrils also start appearing.

The eighth week is made by the beginning of the formation of fingers, ears, upper lip, nose, straightening of the neck, and sprouting of lower limb buds into paddle-shaped structures.

In the ninth week, the baby’s head grows in size and elbows, and arms start appearing. The eyelids and toes also start getting visible.

The umbilical cord becomes visible in the tenth week and the fingers and toes start losing the webbed structure.

The baby is officially a fetus in the eleventh week. The genitals develop this week. Also, the baby’s face becomes broader and the teeth buds for the future start appearing. At this stage, the fetus is capable to start forming red blood cells in the liver.

In week twelve, the intestine is developed in the abdomen and the baby’s facial structure becomes more profiled. Also, the baby’s fingernails start sprouting.

At the end of the first trimester, your baby would be about 2 1/2 inches long from crown to rump and approx. 14 grams in weight.



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