I'm 26+4 with DC3, fifth pregnancy overall.
I know for a fact that the absolute earliest I could have conceived is 3rd June, putting my due date as 23rd February.
The hospital have put my date as 19th February.
DS was ill, then DD, then I had tonsillitis and was ill for two weeks, then DH was working late and (mildly embarrassing as it is to admit) with all that going on we didn't have sex at all in May.
The first time we had sex within the timeframe in question was 3rd June. I'm fairly sure I was ovulating that weekend, we were talking about TTC so I'd been tracking my cycles (I know it's not an exact science though).
By their dates I conceived without even having sex.
I'm aiming for a VBAC (I've had one VB and one EMCS) and going "overdue" will affect my chances, they've already said that if I go a week overdue they'll be booking a date for a section. If I decide ahead of that to have an ELCS it'll be booked for 39wks. This is all based on their dates though, by my dates I'd only be 2-3 days "overdue" and not a week, or for an ELCS I'd only be around 38wks and not 39wks.
Can I ask them to change my due date if I'm sure that they've got it wrong? At my 20wk and 23wk scans baby was measuring in line with my dates too but they've marked him as 'small for dates'.