Nervous again!! Conception date

[Johnson92207]

No regular period. Due date 9/17. First u/s was 1/25 and I was 6w3d (no fetal pole just a sac) dr gave due date 9/17.
Second u/s 2/8 and I was 8w3d. My ultrasounds have been consistent but when did I concieve?

[Johnson92207]

I understand. Maybe I'm just paranoid, I plugged in all the dates and if I conceived with mr wrong, my due date is almost 2 weeks different. besides, I had 2 u/s which would've shown a bigger baby if I conceived around that time.

[AnnieBrooke]

It's not unusual for someone to worry.  Get a DNA test when the baby is born -- not because what the doctor said was in any way suspect (who can better tell you what you need to know than a doctor holding your records in his hand and an early ultrasound)?  But get the test sometime after the baby is born just so you can put your fears to rest.  Some women worry in the face of all the evidence, since it is not absolute and cannot be until they have DNA test results.  I'm not here to tell you whether that is obsessive.

[Johnson92207]

DO you think I'm obsessing over this ? Mister wrong was pull out (which I know doesn't mean anything) but overall likeliness of me not messing with him again and my ex and I got back together and had been ever since is what says to me I'm going crazy for nothing.You get these questions all the time, should I stop worrying about this?

[AnnieBrooke]

Well, from what I understand in your earlier posts, you are asking if you could have conceived from sex on the 13th, not if you conceived *on* the 13th, right?  If the sex on the 13th was unprotected, you have to contend with the long life of sperm.  You could, for example, easily conceive on the 14th or 15th from sex on the 13th.  

Anyway, conception calculators build in a wide range of possible dates of conception to cover the long life of sperm.  If the last time you had sex with Mister Wrong was on the 13th, figure at least 5-6 more days of viability (one paper I read said 7 days, but it is the only one I've seen that says this.  Countering that, I've also seen papers that comment that the sperm is not very lively if it lives 5-6 days and the authors doubt it would be able to penetrate an egg.)  Anyway, even if you add 7 days to the date of December 13, it still doesn't quite reach the date the calculator gives you as an earliest outside date.  You also said in your earlier post that the doctor has confirmed the conception date as being after the range of the first guy.  That is about the best anyone can assure you until you get a DNA test.

[Johnson92207]

So there's no way I could've concieved around the 13th of dec?

[AnnieBrooke]

(Sperm, on the other hand, can live much longer in the woman's system.  Any sex five or fewer days before ovulation would be a candidate.)

[AnnieBrooke]

Here is what the conception calculator I use says.

     Probable date of ovulation:  December 25
     Possible dates of conception:  December 21 to 29
     Due date:  September 17, 2013 (40 weeks)

Conception is within 36 hours of ovulation; after that, the egg is not viable.