Weeks along/due date help

[itwasawendys]

I did an online calculator to see how far gone I am and it said with my period starting on the 1st of April and my cycles being 35 days long, I'd be 4 weeks and 5 days. Out of curiosity I changed the cycle length to 28 days and it still said 4 weeks and 5 days. If it doesn't make a difference how long your cycles are and only matters when you started your last period, why do they ask for the length?

I'd have thought that even if 2 people had the same period start date, if their cycles were different lengths then how far gone they are would be different due to one ovulating slightly later? Or is it the same but the one who ovulated later with the longer cycle might typically have a smaller baby than the one who has a shorter cycle? Unless obviously that baby grows bigger and faster than expected?

Hope you understand what I'm getting at and can shed some light! Thanks

 

[Jessicahide]

I think they ask the cycle time because you may not yet have missed your period or you might be -or+ a few days here or there, but its only really retentive from the first day of your last period, because more days cant physically have past than that... Its all overly complicated... But congratulations on your pregnancy xxx

 

[Miss_Cellany]

They date it from your last period until you have a dating scan to give a more accurate time. It's the only way they can do it but if you know you have a longer cycle and/or ovulated later then you are probably not quite as far along so don't worry if you're put back at your scan.