If You Know Your Exact Date Of Conception

10 Replies
krc - March 1

if you knew your exact date of conception...when they took your fetal measurements... were they accurate in predicting your conception date? If not how far off were they? ( they say I am 1 week 1 day behind than what I know I am )

 

Lin - March 1

Didn't you say on another thread that your cycles are long? That would make sense, because they go by a standard 28 day cycle. As everyone said on that other thread, go by your date of conception plus 38 weeks.

 

krc - March 1

this has nothing to do with my question about my due date.

 

krc - March 1

I didn't know the gestational stage was only 38 weeks...I thought it was 40. Thats why I a__sumed my due date would be 2 weeks later than what they said.

 

krc - March 1

another thing...what do you mean when you say that would make sense? Are you refering to the dr being a week off from the fetal measurements? I only had s_x twice the month I conceived so I know my date of conception. Why do they say im only 17 weeks when it would be 18 weeks from conception?

 

Trish# - March 1

I'm not sure I understand your question but WILL say this. I know for a fact my Ovulation date (had to get fertility treatment to even ovulate!). My FS told gave me a due date based on my last period. But when I started seeing my OB, he moved my due date up 4 days, going on u/s measurements alone. Going by last menst. period is not as accurate b/c women ovulate at various times in their cycle. Even if you know your ovulation date, measurements are more accurate than LMP.

 

livdea - March 1

well...this is a complicated topic! For me personally, I had no period for a few months before I actually conceived. When I found out I was pregnant I had an ultrasound done to find out how far along I was. According to the doctors they can tell how far along you are, pretty much right on the dot if you get an u/s done before 10 weeks. they say all babies develop the same in the fist 10 weeks but then after that, every baby is different. I had one u/s done at 6 weeks and they gave me the conception date of october 16 + or - a day and I had an emergency u/s done at 9 weeks and they gave me the date of the 17th + or - a day...I did conceive on the 16th of october. So...I think they are pretty right on. When I went in and had the u/s done they were telling me I was much further along then what I really was b/c of my LMP...which was wrong. So the question is...did you possibly get an u/s before 10 weeks??

 

krc - March 1

no...ive had only one ultrasound at 16 weeks 3 days. They said at that time I was 15weeks 4 days. Well I conceived on nov. 8th. which would put me at 16w3d !! So they say I am a week off. As though I conceived on nov 15th. I only had s_x on nov. 8th so how often are they off by a whole week?

 

Steph - March 1

Because your baby may not have had a growth spurt yet. One week off on an ultarsound is perfeclty fine. When ultrasounds are given, the measure what your baby is and then he/she is approximatley a certain number of weeks. What does one week matter so much for if you aren't wondering if there's a possibility of who the father is?

 

Sissy - March 1

This is what they taught me in nursing school 3 yrs ago, a normal U/S (not one of the more intense level II) can show fetal development off -1st trimester ,UP to one week, usually accurate with in days..2nd trimester, up to 2 weeks off either direction, a 3rd trimester is not very accurate in doing actual dating and may be up to 3 weeks off. The first trimester is easy to evaluate the fetus as there is a certain pattern for organ and limb development, 2nd triimester there is no such markers except for bone growth, and 3rd trimester it is a c___p shot as they say as the U/S may also be off as much as 2-3 pounds! Hope this helps.

 

Sissy - March 1

Something else to keep in mind, my SIL right now is struggling trying to figure out who is her babies father. She had s_x with her ex husband and then 12 days later had it with her current (now)fiance....the Dr explained to her there is no way possible without an U/S in the first 10 weeks to know who the father might be as every woman has a different timeframe from conception to actual implantation ( there may be upwards of a 4 day span there) and since her periods were never regular ( avg anywhere from 31-36 days) it was anyones guess. That is also why they consider anything between 38-41 weeks as a full term baby, there just are no absolutes!

 

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