Question about gestational vs blood test dating

Hi everyone,

I found out I was pregnant on Wednesday by a positive pregnant test.

Today I'm 4 weeks and 2 days since my last period and after reading a pregnancy book last night it explained that if you are 4 weeks gestational then your baby is 2 weeks old.

The blood test results came back that my levels were showing I was just under 3 weeks along.

Can anyone please tell me if this is fairly normal? That a blood test will tell me that I'm less than my gestational weeks because conception didn't occur until 2 weeks after my period?

I thought I had it all sorted in my head but now I'm wondering if I was wrong and that the blood test should have shown higher levels of HCG to line up with my gestational dating.

The doctor told me to wait a few weeks before going back and he'll perform some more tests and I'll have an ultrasound. I think he's just making sure I get through the next 2 weeks or so. And if I get through the next 2 weeks without complications I'll be 6 weeks gestational does that mean that this is the earliest time they can find something via an ultrasound? I know that right now they could confirm pregnancy by an ultrasound but they wouldn't be able to see very much.

Am I worrying too much? This is my first pregnancy so I'm still learning :)

Congratulations!

do you know what your hcg levels were? the normal range is quite wide, and it can be hard to determine gestation on hcg levels alone. a better measurement is to check hcg levels a few days in a row - but if everything is else is ok, this is generally not necessary.

this is one of the tables that labs can use, but there is a bot of variance between labs too. You can see how some of the ranges overlap.

days
from av range
lmp hcg hcg

25 3w+5d 25 0-50

27 3w+6d 50 25-100

28 4w+0d 75 50-100

29 4w+1d 150 100-200

30 4w+2d 300 200-400

31 4w+3d 700 400-1,000

32 4w+4d 1,710 1,050-2,800

33 4w+5d 2,320 1,440-3,760

34 4w+6d 3,100 1,940-4,980

35 5w+0d 4,090 2,580-6,530

Thanks for your reply HotI.

I never asked for the HCG levels I was too much of a daze to think about asking that. But I guess I could call them and ask for it?

I think I might call the doctors office today and ask them for those details and if the doctor can provide me with another blood test request to measure if my levels have gone up. I had the blood test on Wednesday so if I have it Saturday morning that should be enough time to see if my levels are going up at the rate that they should be?

I think these details may also help settle my concern a bit. It's a nerving experience... fingers crossed thing go well though!

Congratulations Star- let us know how it goes and hopefully you'll feel more confident soon and be able to change your ticker!

Congratulations on your BFP starz!

As HotI said there is a very wide range of normal in HCG results. They pretty much only use it to confirm pregnancy and to check if levels are going up. It is never used to date a pregnancy. Also, sometimes they report the results as weeks past conception rather than weeks past LMP so that gets confusing too.

If you're sure of your LMP they will just use that to figure out your EDD. As for the scan they may or may not see a heartbeat at 6 weeks, I personally chose to wait til 8 weeks as I knew there should be a heartbeat by then, which would save the stress of if I'd had a scan at 6 weeks and they couldn't tell yet.

Good luck, it's so stressful at the start but hope you have a happy and healthy nine months!

Thank you Stephie and Frangipani :)

I've had more of a think this morning and I've decided that I simply had moment of panic and doubt. The night before I had my blood test the doctor told me that only time can tell how things go and unfortunately I seem to have forgotten that. I'm not going to worry too much and I'm just going to wait a week or 2 and then go back for more tests then as he suggested.

I guess for the time being I'll go with being 4 weeks and 2 days right now based off my last AF.

And I totally forgot about my ticker! I'll have to change that when I get home tonight! Thanks for the heads up :)

And thank you all so much for your support. You've definitely helped to make me feel better about this. Bring on the next 9 months!

Hey girls, I just thought I'd drop by and let you know everything is going great with this pg. I had another BT today to see if my levels have gone up and they have. My GP is really happy with how it's progressing and I'll make an appointment to see him for a regular appointment in 2 weeks time.

DH and I are so unbelievably happy and excited about our little one :)

Congrats starz!!!