Expert: Catherine Beier MS CBE - 9/17/2009

Question
Hello, I need help finding out when I got pregnant ok my lmp was 5.10.09 and my cycle is ever 25 days and it last for 5 days I had sex on the last day on my period witch was on the 5.15.09 and then again on 5.21.09, 5.22.09 I had some spotting on 6.2.09 2 days before my period now when I first went to the doctor for my first ultrasound on 7.2.09 she said that I was 7 w and 1day and that my due date was on 2.17.10 but when I counted back 7w and a 1 day it leads me to 5.14.09 but I can't see how that's possiable if I was still on my period and she also say that I concieved on 5.25.09 so whouldnt that mean that I would have been only 5w 3d at the time or they don't calculate from the day of conception can you please hlep me I really need to know my boyfriend will leave me  

Answer
Mika,

No, they don't calculate from the conception date. Pregnancy is either calculated as 40 weeks from the first day of your last menstrual period or 38 weeks from the conception date.  You basically add on two weeks from the conception date - this is because ovulation typically occurs about 14 days before your next period begins.  When counting from your LMP, you're not actually pregnant the first two weeks of pregnancy.  It's just a standard way to count; it doesn't fit every situation, especially if you have long and/or irregular cycles and it's confusing, but that's the way it's done.


So, when she told you that you were 7 weeks, 1 day pregnant, that means you were 5 weeks, 1 day from conception (which would have been around the 24-28th.)  Since sperm can live in the reproductive tract for up to 5 days, then the last date of intercourse on 5-22-09 is the most likely one that resulted in the pregnancy.



Best,
Catherine