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Ovulation Induction

In a normal unstimulated menstrual cycle, around 30 primordial follicles will be recruited and stimulated to grow. However, only one of the follicles will eventually become dominant and develop into a Graafian follicle. While the dominant follicle develops into a Graafian follicle, it will suppress the growth of other follicles and subsequently cause them to degenerate. Thus, during a normal menstrual cycle, only one egg will become a fully mature Graafian follicle. When the maturing Graffian follicle reaches 16 mm in size, there will be a rise in LH hormone release which triggers ovulation at mid-cycle.

In a stimulated ovarian-induction cycle, fertility drugs are used to stimulate the ovaries to enhance the growth and maturation of multiple follicles and yield more eggs of better quality. Therefore, several follicles will develop into mature Graafian follicles at the same time and ovulate at the mid-cycle.

There are two basic types of medication that are used to induce ovulation. Treatment with these drugs has the potential to result in pregnancy if the woman has good quality and quantity of eggs in her ovaries, and if other causes of infertility are not present.

Ovarian Stimulation using Clomiphene for IUI or time intercourse

This is a simple treatment whereby the ovaries are stimulated with oral drugs (clomiphene citrate) to produce 2 to 3 eggs and allow fertilization to occur at timed intercourse. This is the best choice of treatment for those with uncomplicated hormonal disorders and PCOS (polycystic ovarian syndrome).

In this treatment, clomiphene citrate is given daily from Day 3 to Day 7. Follicular tracking by transvaginal scan is done to monitor the growth of follicles from Day 12 of menses and every 2 days until follicles are mature. The mature follicle is defined as a follicle that reaches the size of 17- 18mm. When the follicles mature, the treated couple is advised to have timed intercourse or IUI is performed. After two weeks, a urine or serum pregnancy test will be carried out to confirm the pregnancy.

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Ovarian stimulation using Injectable FSH for IVF (Controlled Ovarian Hyperstimulation)

Injectable medication used for stimulating the ovaries is a follicle-stimulating hormone (FSH). FSH is more potent than Clomiphene and will cause many more eggs to grow and mature. The aim is to produce 5 to 15 mature eggs for the IVF cycle. It’s also known as Controlled Ovarian Hyperstimulation (COH). When the follicles have reached the optimum size of 17 mm, HCG injection is given to trigger ovulation.

There are three protocols for COH that are used to produce many quality eggs during IVF treatment, namely:

  1. long protocol

  2. short protocol

  3. antagonist protocol


The option of the protocol is determined by IVF Specialist and depends on the female’s age, hormone levels and the number of eggs.

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