Fertilization is the process of the fusion of the sperm and ovum which help to start another life. Sperm is the male gamete and ovum is the female gamete. Fertilization begins when the sperm comes in contact with an oocyte. The zygote (the new cell that is formed after fertilization) divides into two, then into 4, 8, 16 cells and so on and finally forms the baby that has more than a trillion cells in just 38 weeks.
How does fertilization take place?
In each ovulatory cycle a mature ovum is released from the ovary normally every 14 days. The female hormones estrogen and progesterone under the influence of FSH and LH control the growth and maturation of ovum. Each menstrual cycle has a pre-ovulatory phase, ovulatory phase and menstrual phase.
- Pre-ovulatory Phase: The time between menstruation and ovulation is called the pre-ovulatory phase. In this period the concentrations of FSH & LH increase several fold. These hormones promote the growth of 6-12 to ovarian follicles in each cycle. However only one follicle matures and becomes mature graafian follicle. This follicle continues to increase it's estrogen secretion. For a day or two before ovulation the follicle starts producing progesterone. During this period the endometrium of the uterus is also repaired and it thickens.
- Ovulatory Phase: The mature graafian follicle releases the ovum around the 14th day of the menstrual cycle. The period after ovulation and before the next menses is called post- ovulatory phase. The ovum after release enters the one of the fallopian tubes and then goes into the uterus. If it is fertilized by a sperm, it gets implanted in the uterus and starts to develop into a fetus.
- Menstrual Phase: If the ovum is not fertilized by a sperm the uterine endometrium degenerates and is discharged for the uterus as menstrual flow. In each cycle there is about 50-150ml of menstrual flow. The menstrual flow contains blood, tissue fluid, epithelial cells derived from endometrium.
When is fertilization and pregnancy most likely to occur?
Fertilization of the ovum is likely if you have intercourse around the time of ovulation. This period is called the 'fertile phase' of the cycle. Ovulation generally takes place l4 days before the onset of a period and in a 28 day cycle it takes place on the 14th day. In people with a regular cycle the probable day of ovulation can be predicted but if you have irregular cycle the period when ovulation will occur cannot be predicted.
What are necessary events for pregnancy to occur?
Events necessary for pregnancy to occur are
- Ovulation must occur and the released egg must be healthy.
- Intercourse should occur around the fertile phase of the cycle.
- There should be adequate number of healthy sperms in the seminal discharge to ensure that a satisfactory number actually reach the egg;
- The environment in your genital tract must be favorable for sperm survival.
- Your internal reproductive system should be in good physical shape.
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