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Does anyone know how to calculate pregnancy weeks?

(15 Posts)
Leanneosaurus Fri 08-Apr-16 12:32:38

I believe I'm 6 weeks pregnant today, my last period was 27th Feb so if I calculate from then, today is 6 weeks. Is that right? I suffered a miscarriage on September 18th and before that my last period was 7th August, the midwife said I was exactly 6 weeks the day I miscarried and I calculated that she must have worked that out week by week from my last period. It's just that I'm having an early scan on Monday 11th to check everything is OK with baby but I'm concerned about not being able to see/hear a heartbeat so early. If I'm 6 weeks 3 days at that point, I figure I'll have a good chance of seeing/hearing it but the reason I'm asking is because I've found conflicting information on Google (surprise) that gives me varying due dates and also some sites say I'm only 5 weeks pregnant.

I know I should really go by how the midwife calculated it the first time, and I did, but once the dreaded Google has put doubts in your mind then it's hard to believe what you already know. I really want to believe that I'm 6 weeks today because if I can get past today with no problems then it means I can relax a little because I've been terrified of not making it past 6 weeks again

Can anyone help?

FuzzyOwl Fri 08-Apr-16 12:35:05

For your first trimester, it is based on how long since your last period (as you say above). However, at your 12 week scan, your baby will be measured and a new date might be agreed and that will be the official date moving forward. Lots of women don't have 28 day periods where they ovulate on day 14, so that is why it is often subject to change.

FuzzyOwl Fri 08-Apr-16 12:35:42

Sorry for you earlier loss and congratulations on being pregnant again. I hope everything goes ok.

Wait4nothing Fri 08-Apr-16 12:41:51

Yes, you would calculate from the first date of your last period. Please remember 6 weeks 3 days is still very early and you may not see s heartbeat yet. We had our early scan at 8weeks as I didn't want to worry myself (though took a few pregnancy tests between finding out and the early sc

Leanneosaurus Fri 08-Apr-16 12:41:52

Thank you :D

OK, well I'll stick to what I thought I knew, I'm 6 weeks today. It'll put my mind at ease I think. I just hope I get to see or hear little guys heartbeat because I'll be terrified again if I can't. I know there is a chance of that because of how early it is but it still won't make me worry any less.

FuzzyOwl Fri 08-Apr-16 12:43:05

You probably will see a heartbeat at 6+3 but it will also almost certainly be an internal scan.

Leanneosaurus Fri 08-Apr-16 12:43:39

I did another test yesterday (a total of 8 now) and it was a very strong positive so I'm sure everything is OK but I can't rest until I have the scan.

LittleLionMansMummy Fri 08-Apr-16 14:21:34

I went for early scan when I thought I was coming up to 7 weeks pregnant (calculated from first day of last period). Instead I was measuring 5+6 but still saw a heartbeat and fetal pole etc. It was an internal scan. I understand though that it's very normal not to see a heartbeat until in 6th week so try not to worry if you don't. I got myself worked up about measuring small but it really is so early it's very difficult to gauge. I've had no bleeding or cramps and still getting all the symptoms so assume when I go for 12 weeks scan it will have developed normally. Good luck.

Leanneosaurus Sat 09-Apr-16 12:49:15

Thanks. Apparently the length of your cycle can determine how far along you are, I'm not really sure though because there's so much conflicting information out there. I guess all I can do is see what happens on Monday, I'm sure everything is fine and I know it could be too early to detect a heartbeat but I really hope I see/hear one because I just know I will worry until the next scan.

FuzzyOwl Sat 09-Apr-16 20:17:17

The length of your cycle can predict based on the fact that most women ovulate 14 days before they get their period. So someone with a 28 day cycle will ovulate on day 14 but with a 31 day cycle it will be on day 17. However, other women (like me) have a shorter LP so this isn't true.

Your pregnancy always starts 14 days before you ovulate but this date will only ever be confirmed at your 12 week scan - and the scan might be out by a couple of days, but the calculation from the scan will be the official one regardless.

Leanneosaurus Mon 11-Apr-16 17:53:35

I had my scan today and it wasn't the outcome I was hoping for. She said I was measuring at 5 weeks, there was a yolk sac and a gestational sac and that was it sitting in the right place but there was no fetal pole. She said she believes the size of the sac to be right due to my 31 day cycle and it all looked normal so far and not to worry......pretty impossible not to worry really. I have to go back for another scan in 10 days. My friend said this happened to 3 out of her 5 children as she had to have early scans with all but a couple of weeks later she saw the pole and saw the heartbeats. I keep trying to hold onto that thought but my heart is telling me the worst has happened.

FuzzyOwl Mon 11-Apr-16 17:59:16

I have everything crossed for you and hope all is ok.

Leanneosaurus Mon 11-Apr-16 19:02:11

Thank you

FuzzyOwl Mon 11-Apr-16 19:08:41

I should just say that it is quite normal to go back a week to ten days later for a rescan and most places won't do early scans before seven weeks for this very reason. You say you have 31 day cycles but do you know when you ovulated? I have a ten day LP so when my cycle is 31 days it is the same as someone who has a 35 day cycle with a 14 LP (the most normal length). If you ovulated late or implanted late, then that would really easily account for the discrepancy of a week. I know it is easy to say and impossible to do, but do try not to worry too much.

Leanneosaurus Tue 12-Apr-16 07:55:04

Well I've been charting my temp and I had a drop on 14th March which would be day 18 of my cycle (also the day I conceived this time and my last pregnancy too) so I assume I either ovulated that day or maybe the day after. I'd say day 18 or 19. I also had a temperature drop after I ovulated 9 days later, which some say could be implantation dip so I know I ovulate later on a 31 day cycle and if implantation occurs between day 6 and 10, well according to the drop, I implanted on the later side too....when I think about this it fills me with hope. I've also woken up today feeling pregnant, I feel sick and faint and very sore boobs (sore boobs are the only constant symptom I've had) but I know with a missed miscarriage you can have symptoms right until the baby comes out.

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