I would go 38 weeks forwards from the EPU date as they would have been fertilised that day...if you use a pregnacy calculator and put the 23rd in as ovulation date it should be pretty close

I get this result:

Results: Your estimated due date is 14/01/11, which is 7 months from now.

Your pregnancy will be full-term until 28/01/11.

The estimated date of conception is 23/04/10.

The estimated fetal age is 6 weeks and 5 days.

hope that helps.....