SingleSoon, Do you know if the ultrasound age was based on a 40 week or 38 week pregnancy calendar? If not, post your due date which is the same regardless of which type of gestational age calculation was used.
The LMP method is very inaccurate as the time between your LMP and ovulation is the one part of your cycle that is variable and not constant.
Using a scan, they measure the fetus from the date of conception/ovulation to its current size. That part of your cycle is much more constant and the scan dating thus much more accurate.
The confusing part is that some facilities will then add on 2 weeks on to the age to a fictitious LMP date (the 40 week calendar). Your due date is however always constant, regardless of the 38 or 40 week calendar.
So with a due date of June 15, your ovulation/conception date was around September 22. It can be off by 2 days but 95% of all woman will ovulate within 2 days of that date - either before or after.
That will mean that sex between Sept 18 and Sept 23 could have gotten you pregnant.
Since you only had baby making sex on Sept 26 and Sept 30, it is clear that either the scan measurement was inaccurate or that you are one of the 5% of woman not ovulating in the window 12 to 16 days before your next menstruation.
So lets search for something more closely matching your sexual history. Going from your LMP based due date of June 20, you ovulated on Sept 27. That will mean that sex between Sept 23 and Sept 28 got you preggers. Sept 26 is actually your peak baby making day in this scenario. So this fits your situation perfectly.
So if I were a gambler, I would place my money on September 26 as the date you had sex that got you pregnant.
No August is wayyyy too early. The risk from period sex is more academic than pactical. I am sure there are some unlucky women somewhere that got pregnant from period sex, but it can only happen if your cycle is totally and utterly abnormal and screwed up ( no pun intended).
I do not understand why Sept 22 should confuse/concern you? I showed you how to determine the ovulation dates according to your due date for the scan and LMP methods. This gives you a range of days you could have had baby making sex. Sept 26 matches perfectly with the LMP method. What is causing the confusion??
SingleSoon, Anything is possible. It is however very unlikely that with those due dates it would have hapened.
Early scans are accurate to within 2 or 3 days. After sperm lived 3 days inside you, they are in a bad shape and not really capable of fertilizing your egg. So together this gives a maximum variance of 6 days earlier for the sex that got you pregnant.
Sept 13 is 9 days before your most likely ovulation date (Sept 22). If we use your LMP EDD, you ovulated even later. It is very unlikely that sex on Sept 13 got you pregnant.
susan862003 u seem very helpful so was wonderin if u culd help me as im am worrying constantely and need sum reasurance i am 15 weeks and 3 days pregnant 03/12/2010 my edd is august 31st and my lmp was november 24th and ended around the 29th i have a normal 28 day cycle and using online calcutors i worked my ovulation day out 2 be december 8th and when i went for a scan i was told the baby was a good size 4 my dates and she put me at the exact dates as i had calculated so surely my conception date of december 8th must be pretty accurate the problem is on december 10th me and my bf had a breif split and i had a 1 night stand were as prior 2 ovulation i slep with my partner from november 29th every night til december 3rd do u think that theres a chance my bf is not my babys father ? i wuld really be greatful 4 any comment u can give me....
oh and 1 more thing with my 1 night stand we had sex more than once but the guy did not ejeculate inside me i no this doesnt always work but jus thought ild mention it and my partner always ejeculates inside me as we was trying 2 conceive....
How long after sexual intercourse does implatation bleeding occur? Is there any way that the 14th could have been implatation bleeding (not period) and the scan be off by that much?
Thanks for all your help!