How Pregnancy Occurs - Events Following Conception - Part I

This is a question in many women's mind that what exactly happens when pregnancy occurs and how the baby develops inside the womb as pregnancy progresses. Seeing their baby on the monitor during first ultrasonography is an exciting and emotional experience for many women. (I was no exception!) Read on to find what happens when you conceive and how your baby develops with time.

Ovum is released from the ovary sometime around your mid-cycle. It is then picked by the fallopian tube of the uterus (womb) i.e. the uterine tube. The union of the sperm and the ovum takes place in the uterine tube. This is known as fertilization. It leads to the production of a single cell called zygote.

• Ovum + Sperm = Single cell called Zygote [Fertilization]

Sex of the baby is determined by the type of chromosome contributed by the father's sperm. X chromosome results in a girl child and Y chromosome results in the development of a boy.

• Ovum (X) + Sperm(X) = Girl (XX)
• Ovum(X) + Sperm(Y) = Boy (XY)

Single celled zygote undergoes a series of divisions. About 30 hours after fertilization first division occurs resulting in the two celled stage. After this, segmentation continues through 4 and 8 cell stage till a cluster of 16 cells is formed which resembles in appearance to a mulberry. This is known as morula. All this happens in the uterine tube. On the 4th day morula enters the uterine cavity. Inner cells of the morula form the baby and outer cells form the membranes which provide protection and nutrition to the baby.

• 0 hour - Fertilization -> single celled zygote (In uterine tube)
• 30 hours - Two cell stage
• 40-50 hours - 4 cell stage
• 72 hours/3rd day - 12 cell stage
• 96 hours/4th day - 16 celled morula (Enters the uterine cavity)

Morula remains free in the uterine cavity till the 5th day. Some fluid enters the morula resulting in a cystic structure called blastocyst. On the 6th day from fertilization (20th day of a regular 28 day cycle) blastocyst sticks to the wall of the uterus and continues to penetrate till the 10th or 11th day. This process is known as implantation or nidation.

• 5th day - Blastocyst formation
• 6-7th day - Blastocyst starts to penetrate uterine wall (Implantation started)
• 9th day - Penetration continues
• 10-11th day - Implantation completed.

I tried my best to explain a complicated subject. Hope you were able to grasp. Enough for this post now. I'll discuss further development in the next post, Events Following Conception-II.

 Also read:

How To Know If You Are Pregnant-5 Early Signs

See list of all articles on Pregnancy