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OT - Dating Ultrasound Question

Annoyed1's picture

So, this is my first pregnancy and I'm a little confused. The start of my last period was Dec. 2/16. When I went to the doctors, they told me my due date was September 8, 2017. I just came from my first ultrasound and they said that I am 10 weeks pregnant today (when I should only be 9 weeks). How can I be 10 weeks? That would mean that I was pregnant a week before my last period?!?! I'm confused. On a side note, it was INCREDIBLE seeing the baby moving around and it's little heart beating on the screen!! 167 beat per minute too!!! I've never experienced this feeling before and it's amazing Smile


Annoyed1's picture

Ok! Thank you. I was just a little confused when he said that. I guess I'll wait to see what the doctor says when I go back.

Annoyed1's picture

Smile I'm really hoping for a boy, although I would be equally as happy with a little girl! I'm just leaning ever so slightly to wanting a boy.

Annoyed1's picture

Yeah, the technician said that my new due date is now Sept. 1 and not Sept. 9. I guess I'll just wait to see what the doctor says! 10lbs?! I'm hoping for a little less than that Blum 3 But as long as he/she is healthy, I'm happy Smile I'm getting really excited!!! This all made it so real for me.

Annoyed1's picture

Lol! Yes, I have a feeling (I could be wrong though) that this baby will be earlier than Sept. Either way, I'm getting really giddy Smile

Annoyed1's picture

Lol! Don't jinx me Blum 3

And, thank you. I feel like I can actually start to enjoy it now that I saw the baby moving and saw that there's a heart beat Smile

Peridwen's picture

Both times my due dates changed with the ultrasound. Both times my OB said the change was minimal and there was no reason to officially change our date based on that. BS2's date changed to later since he was small to begin with, but when he was born 2.5 weeks early (technically week 37, so only a couple days before "full term") he was 8lbs 13oz. So plenty big and the pediatrician said he was healthy normal baby.

moeilijk's picture

They look at the size, but they also use a standard 28-day menstrual cycle. So if your normal cycle is longer or short, or all over the place, that could mean that actual conception took place a few days either side of the calculated date of conception.

WokeUpABug's picture

You probably ovulated early. Most women ovulate day 14 (day 0) is start of period. But if you ovulate on day 7 then you'd be one week farther along than predicted by the start of your last period. Remember the way OBs date your pregnancy week 1 is the week of your period. Weird right? So they aren't saying you were actually pregnant before your period, just that you didn't ovulate when you thought you did.

Anyway congrats!!!!

SM12's picture

When I was trying for my BS, I swore on my life I was pregnant in May. I took at home pregnancy tests and they were negative. I had my period and the following month (June) I found out I was pregnant. The following month, I spotted but had another US and all was fine. My due date changed several times based on my Last period, then the US, etc. I ended up having him two weeks prior to the due date based on my period. And let me tell you, he was not early. For two weeks prior to having him I could feel him practically in my birth canal. I could barely walk because of how he was positioned. I think I was actually pregnant when I thought I was in May. I just happened to have a few months of slight period after I was pregnant.

Thumper's picture

awwwwww congratulations!!!!!

I love seeing baby posts.

Being pregnant is wonderful.

Looks like you have great feed back on your question so I will just say Congratulations again and enjoy this time. IT IS PRICELESS!!! Smile

blueorblackink's picture

I like your due date. I have a DS born on 9/9 and a DS born on 9/7.....

I like to think the cold and the holidays were responsible....

Rags's picture

September 8 is 40 weeks from Jan 1 which is likely what the doc initially estimated as your likely date of conception.

You likely conceived ~3-4wks after your last period began.

At least that is what my quick obstetric layman's eyeball scan of the calendar indicates based on the due date the pro's have estimated. It is my understanding that estimating due dates is not an exact science and is based on an early level of pregnancy hormones. Estimated age of the peanut is based on measurements taken during the ultrasound. At best a due date is an estimated SWAG based on several variables at play during the early pregnancy weeks.

My SS was born 5wks early and was right at 5#s. This was all pre Rags of course. But I have heard the stories countless times over the decades. One reason we had no more spawn was because I was not willing to jeopardize my DW's health with another pregnancy after she had sever toxemia/Pre-eclampsia with SS.

Congratulations on the little one.