Confused by scan dates. Could do with advice please?

[StarryEye1980]

I am currently pregnant, the pregnancy was not planned.  I have had two scans but am still confused with who is likely to be father of my baby.  I previously was having a casual relationship with "Guy A" but met "Guy B" decided to have a serious relationship with him, then found out I was pregnant.  I used condoms with both guys which is partly why I am so confused about my pregnancy because there was no sign of breakage or leakage to my knowledge I have asked both men say that as well.

I last slept with Guy A in the early hours of 24th Feb 2013

The last periods I had were 30th Jan and 27th Feb (I always have very short periods, 2 days and 28 days between).

I slept with Guy B (my boyfriend) on 9th March.

My period was late, April 5th I done prg test and it was positive.

16th April I had a private u/s scan which dated me 6wk6d pregnant and ties in exactly with my last period and the baby being my bf's. Due date 4th Dec 2013

I had my NHS u/s scan on 20th May expecting to be 11w5d but they dated me 12wk5d putting me forward by a week. (Due date 27th Nov 2013).  This suggests I would have concieved on 6th March and I am now concerned this baby might not be my bf's.

If anyone can offer me advice on this I would be very greatful. Thanks.

[AnnieBrooke]

Thanks, Starry.  

[StarryEye1980]

Thanks so much for your advice.  It has helped to talk to someone freely about this who is detached from my situation.  You are correct in saying I am letting my anxieties take over some what and it will help to focus on other things.  I am a mum already, another child wasn't in my plans but I know it can only be a blessing which is meant for me, as is the fact that I have a very supportive mother and a loving partner who is standing by me.

I really appreciate the time you have spent responding to me.  Thanks again and you take care too Annie :-)

[AnnieBrooke]

Even with it being a short month, it is quite a stretch to presume that a sixth-week ultrasound would be wrong by 11 days or even 8 days, especially when you had a period in between the men (unless you think the private place you went was simply a bunch of charlatans).  When she said "Have you seen the size of what they have to measure that early," well, that is what good-quality ultrasounds do.  My IVF clinic uses ultrasounds to measure the thickness of the uterine lining (a very fine measurement, certainly not as big as a sixth-week embryo) and they do 5th, 6th and 7th week ultrasounds many times every day.  The better machines are very accurate.

Basically, you have a choice as to what to believe, which is at this point probably going to come down to how much counsel you are taking from your fears, versus what the numbers are really saying.  We get a lot of posters whose numbers are closer than this and more iffy, yours are really not very close (especially with that period in between the sexual events).  This suggests that your anxieties are ruling the show instead of your logic.  Here is what the facts and figures are saying:

Choice 1:

- early ultrasound done in the absolute best week for dating pregnancy
- done at a private place (presumed top-quality equipment)
- due date correctly identifies the first day of your last period
- for which due date, conception calculator says:
        First day of last menstrual period -- February 27
        Probable date of ovulation -- March 13
        Possible dates of conception -- March 9 to 17
        Due date:  December 4

Choice 2:
-  later ultrasound, done in a time frame where women are cautioned that it could be up to several days off because of differences in the rate of baby's growth
-  done at NHS (who knows about the quality of the equipment)
-  you had had a period in between one guy and the other
-  due date does not correctly project the first day of your last period
-  for which conception calculator says:
        Assumed first day of last menstrual period:  February 20
        Probable date of ovulation:  March 6
        Possible dates of conception:  March 2 to 10
        Due date:  November 27

Please note that having had a period in between the men or not, neither range of possible dates of conception includes February 24.

OK, so, the point is, you're anxious.  Addressing anxiety is an important part of pregnancy management.  To help with this:

1.  Be ready for the fact that each time from now on, when you get an ultrasound, they might adjust your estimated due date.  So what, the baby will grow at its own rate and it might or might not match the averages.  It does not mean the baby got started at a different time.

2.  Set your plans, be sure of your job, confirm the roof over your head, work out your baby's care, find your support system.  These things carry over into the pregnancy itself.  If all is in flux and you have big existential questions in your subconscious, the pregnancy is not going to be calm.  The reverse is also true.  Fortunately the certainty you want is something that can be created with good planning.

Take care, and enjoy the fact that you're going to be a mama!

[StarryEye1980]

I was more thinking it could have lasted for 6 or 7 days as Feb is a short month, meaning that the scan would only be out by 5 days...about the same as it has to be the other direction for it to be my bfs.  Like you said, I'm taking a bit hope from the fact that I bled on the 27th and that it would be more unusual for me to ovulate around this time given that my periods have always been regular with 28 day cycle.  I have never tracked ovulation though, so I guess I am thinking of every possibility.  I had wondered about the earky scan and how accurate it might be.  When I got my second scan and obviously got worried when my date was put forward, the sonographer pretty much snapped at me that her scan would be more accurate than the early one and remarked "have you seen the size of what they have to measure that early".  Her lack of reassurance made me more anxious.  It was the midwife whom I saw next who going by the new scan date told me conception date would have been around the 6th March.  Which as you know from my sexual activity is impossible.

[AnnieBrooke]

The six-week scan is not going to be wrong by sixteen days.   It probably is going to be spot on, or off by one day.  And you had a period in between.  You think Mister February 24 had mighty sperm that lasted through a period and for two weeks?  Think again.

[StarryEye1980]

I definatley never had sex with anyone between after the 24th Feb until 9th March.  I guess I am worried because somehow the scan is out.  Maybe my baby is just measuring a bit bigger but It's just the fact like you said that sperm can live in the body nearly a week and I am worried in case the scan turns out to be wrong the opposite way (and perhaps the baby is measuring smaller).  I don't know what the chances are, I am finding this hard to deal with, it's making the pregnancy emotionally hard for me...but maybe I am worrying for nothing?  Thanks  a lot for your reply.

[AnnieBrooke]

In other words, it could not be the guy from February 24 according to both scans.  That leaves the event from March 9, unless you had sex March 6 with someone you haven't mentioned.  

[AnnieBrooke]

Why do you think that if you conceived on the 6th of March, the baby is not your boyfriend's?  If the last time you had sex with anyone else was February 24, March 6 is too far away for his sperm to have anything to do with anything.  (Sperm can last up to 5 or 6 days in your system, but in this scenario you are worrying that it lasted for 13 days.  No, it didn't.)