DNA test is the only fair thing to do when the possible dates are just 4 days apart, if those are really the dates. If op knows that she only had the one encounter with the ex that early, and she is CERTAIN that her projected due date is right, she might look a little later. How did the projected due date get named? Was it by an ultrasound at the 7 week point? If not, it might be off.
I have included two calculators along with their url's with a little information regarding dating pregnancies:
Ovulation, and therefore conception, occur 14 days before your period was due and you can get pregnant from making love up to 5-6 days before ovulation happens. If you have a 28-day menstrual cycle -- which is assumed by many healthcare providers -- that means that you ovulated on day 14. If your cycle is a few days longer, you probably ovulated after day 14, and your baby may arrive a few days after your estimated due date.
This pregnancy conception and due date calculator let's you know when you could have made love and when you did get pregnant. Your due date is calculated by adding 266 days (38 weeks) to the date of ovulation/fertilization.
This due date conception calculator answers your question: "If this is my due date, when could I have gotten pregnant?"
Based on your due date the BabyMed conception date calculator will interactively calculate backwards and let you know a range of days during which sexual intercourse may have led to conception.
BabyMed Conception Date Calculator
Your estimated conception date was between Wednesday, December 30, 2009 and Tuesday, January 05, 2010.
http://babymed.com/Tools/Pregnancy/Conception_Date/Default.aspx
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Another one:
Conception Calculator
Conception Calculator estimates probable conception dates from Birth, LMP and Due dates.
These are probable conception dates based on an average 28 day cycle.
To use the calculator:
Choose either the Due Date / Birth Date
or the First Day of Last Menstrual Period,
Enter the date, and
Click the 'Calculate' button.
Birth / Due Date:First Day of LMP:
Results: First Day of Last Menstrual Period: December 21, 2009
Probable Date of Ovulation: January 4, 2010
Possible Dates of Conception: December 31 to January 8, 2010
Due Date: September 27, 2010 (40 weeks)
http://www.baby2see.com/conception_calculator.html#ConceptionCalculator
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You can Google "conception date calculator" and they will pretty much say the same thing with maybe very minor differences. I'm definitely not a know it all, but I really think you're forgetting that your last menstrual period is calculated in that 40 week period.
Penswriter-you're right. However, you're due date was a week earlier than hers and you got pregnant Christmas week, which means she shouldn't be looking at December 20th- 24th as her dates. She should be looking later. I do agree with you that ultrasound can be off when calculating due dates, so it would be smart to have a test done when I think about it...
i'm with mjsk - i got pregnant christmas week in 2008 and my due was sept. 20. (since it was multiples i went into labor 6 weeks early)
op - since you had sex with 2 men within 2-4 weeks time (docs go based on lmp and u/s can be off by up to 2 weeks) you'll need a paternity test.
Not always true. Both of my daughters were conceived in December, the last one around Christmas. My daughter birthdays are Sept 11th & Sept 21. My cycles are 30 days. Medically speaking; a woman cycle can range from 21-40 days and still be considered regular. Anything outside of that would be deemed an irreguler cycle. If the young lady only had sex with these two at that time frame, then her conception date is still about right.
it might be ex s sorry.:(
I honestly don't think you became pregnant from either of those dates. A pregnancy lasts about 38 weeks from conception, but because we usually don't know our exact conception date, it is counted out as 40 weeks from your last period because the average cycle lasts 28 days, making your most fertile time around day 14. You should be looking around January 4 as your actual conception date. So, counting 40 weeks out, your last period was probably around December 21, and 14 days from that is January 4.
You will have to get a DNA test to find this out. The reason for this is; there is no logical way of finding out without a test. After ovulation, a egg will only last 24-28 hours. But sperm can live between 2-5 days inside of the uterus. So with only a 4 day gap in between partners, it's anyone's catch. So you will have to get a DNA test. Wish you the best.