What is follicular monitoring?

Many couple who wish to conceive, are advised a follicular monitoring to plan the natural or IVF pregnancy. 

Follicular monitoring is a simple process done by sonologist/radiologist/fertility specialist, where they count and measure eggs in each ovary at regular intervals during menstrual cycle. When the egg reaches a certain size (usually more than 18 mm in diameter), it can ovulate (i.e. egg release) any time in next 3-4 days. This is the time period, when the chances of successful pregnancy is maximum. 

In most set-ups, follicular monitoring starts at Day 3 of cycle, when a baseline egg size is taken, to plan the follicular monitoring. At this time, some people may have a cyst or a large ballooned egg from prior cycle. In that case, it is sometimes better to abandon the study in this cycle, and better to proceed again in next cycle, when cyst is gone. Although, its not a hard and fast rule, and pregnancy may very well happen even if cyst is there. If there is no cyst, size and number of eggs are taken. Usually, at this time i.e on day 3 of cycle, egg sizes are 3-5 mm.

On day 3, gynecologists/fertility specialists prescribe some medicines to grow the egg, which is taken for 4-5 days. By day 7-8, after induction (i.e. taking these prescribed medications), eggs grow close to 10 mm. This is confirmed by scan on day 7/8, when again size and number of eggs is counted. Sometimes, eggs are overgrown, while sometimes they don't grow. If we have good number of eggs grown close to 10 mm at this time, chances of success are higher.

Then, radiologist/gynecologist decide to monitor the eggs closely on alternate day, and then on daily basis. Once the egg reaches a size of 16-18 mm, it may naturally ovulate and release the egg. If it rather reaches 20 mm and doesn't ovulate, a gonadotropin (HCG) injection is given, to release the egg. Egg release is seen on ultrasound, as some fluid released around ovaries, and also the sudden shrinkage in size of egg.

Now, this released egg is healthy for the period of 12-24 hours, whether to try natural pregnancy or IVF.

For more technical details, you may refer my article "follicular monitoring".