Expert: Dorothy H, LCCE - 10/12/2010

Question
HI I HAVE QUESTION FOR YOU MY LAST PERIOD WAS APRIL 8 IT LAST 5 DAYS I HAD SEX WITH PARTNER 1 ON 12 MY LMP WENT OFF 13 THEN ON APRIL 18,22,24 PARTNER 2. I HAD TREE U/S  MY FIRST ONE WAS MAY 18 AT 5WEEKS 5 DAY, 7WEEKS 6DAY AND 9WEEKS 5DAY THEY SAID IT LINE UP WITH MY LMP AND I CONCEIVE AROUND APRIL 22. THE THING THAT GOT ME KIND OF SCARE IS THAT I HEARD SPERM CAN LAST UP TO 7 DAYS AND IF THAT TRUE IS THERE ANYWAY PARTNER 1 CAN BE THE FATHER? AND WOULD THE U/S PICK UP IF THE BABY WAS BIGGER THAN 5WEEKS AND 5 DAYS AND IT WAS A EMPTY SAC AT 5 WEEKS. I AM BACK WITH PARTNER 2 HAD HAPPY I JUST DONT WANT THIS TO BREAK US APART AT THE END. DO YOU YHINK THERE ANYWAY I GOT PREGNANT FROM APRIL 12 WHILE MY PERIOD ON ? AND LAST QUESTION WOULD THE U/S PICK UP A WEEK BIGGER 6 WEEKS 5 DAYS  THAN A 5 WEEKS 5 DAYS  GA  

Answer
I've already answered this for you, but I'll try to answer your questions again and hopefully put your mind at ease.

1) Sperm can live for 3-5 days in the fallopian tube.  Very rarely up to 7 days (that is not the norm)

2) From the information you gave, Partner #1 is not the father.  Even if the sperm lived for a week (highly unlikely, especially since you still had your period at the time and that environment was not conducive to sperm living for a long time)

3) Yes the u/s would have shown a lot more if you were really 6 weeks 5 days.

Is it theoretically possible that Partner #1 is the father - yes.  I would say much less than 1%.  It would require the sperm to have lived for a week (which is rare, and only under optimal conditions, which you did not have) and it would require that 3 first trimester ultrasounds were off by 3 days, which is the outer limit of how off they can be.

Also, you had sex with Partner #1 once, and you had sex with Partner #2 three times.

Based on the information that you gave, I would say that the odds that Partner #2 is the father is over 99%.

I hope that helps.

Dorothy H, LCCE