starcatcher3355 replied: "Overstimulation is rare with clomid. There is only a 10% chance of having twins and it's usually when you start on cycle day 3 or sooner.
Women have lots of eggs that race to be the one that matures. Around cycle day 6, the battle results are in and the biggest follie becomes the one to ovulate while the others support the development of the lining and die off. The eggs are recruited to begin this process at 120 days but they accelerate in growth on cycle day 3 so by starting on cycle day 3 you're increasing the odds of more than one egg reach maturity but it's a 10% increasing which isn't high. Doctors choice to start patients on cycle day 3 in hopes to making more than one develop so that at least one will implant.
If you start on cycle day 5, you're increasing the odds of one egg mature better by boosting the fsh that causes the egg to mature."