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Calculating conceiving date - Online Doctor Chats

Date : 21-Feb-2012
User rating for this question
Very Good Posted in: Getting Pregnant
Answered by

General & Family Physician
Practicing since : 2004
Answered : 37 Questions
User :   My ultrasound measured baby at 9 weeks. Does this mean based on LMP or when I concieved? If the weeks are based on LMP then it would mean i'm 7 weeks right? If not, then does it mean I concieved 9 weeks ago?
Doctor :   Hi
Doctor :   Let me read your query
Doctor :   I am Dr. here
Doctor :   May I know your last menstrual period?
User :   A normal period was 3/13/10. Then I had some light bleeding on 3/29/10
Doctor :   When was the ultrasound scan done?
User :   June 2
Doctor :   Ok
Doctor :   On 29th, was it just spotting?
User :   I just want to know if the baby measures at 9 weeks does that mean when the baby started growing
Doctor :   Ultrasound shall detect it based on the size
Doctor :   and cannot be considered as very accurate
Doctor :   clinical history of LMP is very much significant
Doctor :   usually 2 weeks of variation shall be there b/w the 2 values
User :   Well could I have started bleeding again due to stopping my birth control
Doctor :   and the same is in yours
Doctor :   Ok
Doctor :   So, now for practical purposes you should go by your LMP
User :   Because the 3/13 period was normal then I was taking birth control for 1 week then i started spotting 3/29
Doctor :   Ok
Doctor :   That has to be considered as LMP
Doctor :   meaning the 29th
User :   would going by 3/13period sound practicalfor me being 9 weeks or the 3/29
Doctor :   So you were scanned on 65th day from your LMP
Doctor :   meaning 9 weeks after 3/29
User :   Yes but I thought it takes 2 weeks for the baby to implant and stuff
Doctor :   Right it does take
Doctor :   ultrasound goes by the weight of the fetus
User :   So if the 3/29 would be LMP then when did I concieve
Doctor :   2 weeks from then
Doctor :   usually
Doctor :   again if it was after the frank cycle, then your ultrasound does sound more accurate
Doctor :   considering 3/13 as LMP
User :   What is Frank cycle
Doctor :   that means conceived around 3/29
Doctor :   frank cycle is the normal period
Doctor :   like on 29th you did mention it was just little blood loss
User :   So then that would mean since the u/s says I'm 9 weeks then i would count 9 weeks back to find out when I concieved
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