Dating scan

[Letmegetthisrightasawoman]

My dating scan put me 5 days ahead of where I thought I was. I normally have 28 day cycles on average. I had sex on CD10 and CD13. I'm assuming the calculators assume you conceive on CD14 in a 28 day cycle, meaning you are 14dpo when you miss your period (and are four weeks pregnant). Even if I did conceive on CD10, surely that would mean I am 4 days ahead, not 5? Can dating scans be out by a day? With my first the dating scan matched my dates perfectly. This time I did conceive on the first cycle I was off the NuvaRing though, could that affect ovulation?

It's normal for them to move your date depending on the size of the baby - I'm having twins and mine has just been moved by 5 days because one twin is measuring bigger - I had IVF so 100% certain on dates

Congratulations! I thought the whole point of the dating scan was that babies develop at pretty much the same rate in the first trimester? So they can tell gestational age by looking at the size and there is no such thing as a large or small baby at this point yet? DS was a whopper (8.14 at 38+4) but my edd based on the scan was the exact same as the one I worked out based on my LMP. I'm just a bit concerned because my gut feeling is that DS wasn't ready (ELCS) and I want to avoid being induced before it's strictly necessary with this one.

My 12 week anomaly scan made me 6 days more pregnant than my dates, so similar to you. He then ended up being born at 38+3, so a fair bit before I would have liked.
I spoke to my midwife about the hospital's dates not actually being biologically possible, and she wasn't fazed at all.
Just try to remember that anything after 37 weeks is considered term, and babies born well before this are usually absolutely fine too.

Also, you don't have to agree to any kind of intervention (barring emergencies) if you don't want them or don't think your baby is ready yet. It's your body and you can refuse an induction or request one at a later date.

When I had my dating scan with my DD, I was put 6 days ahead. I was tracking ovulation, so knew it was impossible.
She ended up being born on the exact due date the 12 week scan had predicted. Even though its recorded as born at 40 + 0 weeks, I know by ovulation and LMP, she was born at 39 + 1.