Pregnancy Dating

[ReturnofSaturn]

Hello,could anyone help me with this..

Iam around 21 weeks pregnant. But am getting confused, is it still dated from my last period or does it go off the gestational age they got from my scans?
Confusion not helped by utter shit doctors at the docotrs clinic I was using (have just switched doc's as got sick of this),
Got first midwife appointment on Saturday at the hospital and want to be clear on how far gone I actually am!!

I'm really rubbish at the terminology of it, but I asked the sonographer and she said they add two weeks onto the gestational age. So when the computer measures your baby at the scan, it automatically adds on two weeks

I had ivf so know exactly when I got pregnant and they still changed my dates!

It's a bit of both as far as I'm aware- before your '12 week' scan they take from the date of your last period, however the first hospital scan you have is actually known as a dating scan, so they'll measure certain parts of baby during that and then calculate your due date and weeks from that as this is supposedly more accurate. Lots of people (including me) find that their due date shifts at the dating scan. After that your due date shouldn't change and you'll stick with that for the rest of pregnancy, does that make sense? It's partly why babies are considered 'full term' anytime between 37-42 weeks, as there's no single guaranteed way to determine exactly when conception occurred! Welcome to one of the many uncertainties of pregnancy OP! X

Sorry, meant to say that in past tense as you've already had the scans, so the short answer is that you take the date your scan gave you, not from last period. (I'm 37 weeks and being able to read and respond coherently aren't my strengths at the moment!!) 😂

Ok, so I should be going off the dating scan- is that the 12 week one?

They take i from the last period date. Then add 1 week in it. The EDD doesn't need to meet it necessary. Mostly women get labor pain before 1 week of EDD. There are very rare cases, in which EDD meets. My EDD was 7 September while I gave birth to 29 August. I always observed that baby comes before one or two weeks of EDD.It happens between 38 to 39 or 38 to 40 weeks. If you doesn't remember your period date exact, then doctor finds the exact delivery date from the scan in the 4th and 5th month. They add one week in it. This one week is you can say safety measures. Normally baby scan in 4 or 5 month can tell you actual time. In the scan, doctor measures baby size and weight. Which helps to calculate the exact figures. I was forgot my exact period date and they find it by baby scan.

The date you're given at the 12-week scan is based purely on the baby's measurements, regardless of when your last period is, and is the one they tend to go off of as it's generally the most accurate. However, it assumes that all babies are the same size at 12 weeks (and studies of twins and IVF pregnancies have shown that this isn't necessarily the case) and that all women have the same average gestational length of 40 weeks (when studies have shown that different ethnicities tend to have longer / shorter). So take it with a pinch of salt.
Also, in the UK any time from 37-42 weeks is considered "normal" to deliver at, so the concept of a specific "due date" is kind of moot anyway.

They take the date from the 12 week scan... it's not always right but that's the date they use.