Hi, Thanks for the query. If you have a regular 23 days cycle then we must subtract 5 days from the date calculated by using the routine formula. The total duration of pregnancy is 40 weeks that is 280 days. Count 280 days from the date of your last menstrual period. in January: 29 days February: 28 March: 31 April: 30 May: 31 June: 30 July: 31 August: 31 September: 30 Total: 271, we need 9 more days to make it 280, so October : 9 days Total 280 days Now subtract 5 days from this as you have a 23 days cycle So in October only 4 days So your calculated EDD is October 5th. Please understand that a difference of a few days does not make much of a difference. Only 2% women deliver on the exact date, rest of them all delivery 2 weeks prior or 1 week later. So this is an issue only if you have any complications like baby with less growth or raised blood pressure etc. So do not worry so much about the date. Inform your doctor that you have 23 days cycle and he/she will correct the dates by subtracting 5. The heart beat of 11 at 6 weeks as such does not make much of a difference according to research. However it may be an early indication of an impending abortion. So discuss this with your healthcare provider and start progesterone tablets as they help to maintain pregnancy. Hope this was able to answer your query. Have a safe pregnancy and delivery. Feel free to ask any more queries that you may have and I would be willing to help. Dr Madhuri Bagde Consultant Obstetrician and Gynecologist