(Closed) Long cycles and pregnancy weeks

posted 7 years ago in Babies
Post # 3
959 posts
Busy bee
  • Wedding: July 2009

First off, congratulations!! I take it you were not trying? What a fun surprise!! So, you do in fact count from the first day of your last period. However, for women with long cycles, such as myself, you actually count based on when you ovulate. For women with regular cycles, this is 2 weeks after their first day of their last period. For women with longer cycles, or cycles that vary, the only way to figure out how pregnant you actually are is to either calculate based on when you ovulated, if you know/were trying/paying attention, or by when the doctor measures the size of the baby. So for example if you ovulated at 3 weeks instead of 2, and have a cycle that lasts 5 weeks, you’d actually only be 4 weeks pregnant based on when you ovulated rather than from your last period. Is this making sense? It’s a little confusing to try to type out. Or maybe it’s my pregnancy brain! 

It sounds like you don’t know when you ovulated, so you will probably have to wait for your doctors appointment to know for sure; however, if you got a negative test then 3 days later got a positive, you’re probably only like 4 weeks pregnant or so, maybe 5. What would you be based on if you went by your last period? 

Post # 4
2538 posts
Sugar bee
  • Wedding: November 2009


Did you take any ovulation tests or anything?  You pretty much always ovulate about 14 days from when your period should start.  So you could probably count back about 14 days from your positive test and calculate that way.  It stupid that drs use an average that’s not really average to figure it all out!


Post # 5
2095 posts
Buzzing bee
  • Wedding: September 2011

If they are not sure then they can get an accurate date from a sonogram. I couldn’t remember the date of my last one and that is what they did for me.

Post # 7
959 posts
Busy bee
  • Wedding: July 2009

Well I have long/irregular cycles too and I ovulated on day 21 if memory serves. I found out I was pregnant with a very faint positive at 10 or 11 dpo. I was only 3 weeks 4 days or something like that. Like I said, if your first test was negative and 3 days later it was positive, most women get positive results about 14 days after the ovulated so say the day you took the test and got a negative you were only 11 days pregnant, but 3 days later you were 14, that puts you at 4 weeks when you found out. It’s a little rough and could go a few days on either side but I think it’s safe to say you’re about 4 weeks pregnant. 

Post # 8
1126 posts
Bumble bee
  • Wedding: April 2011

@aguilpul: If you have long and unpredictable cycles, then it’s the part of your cycle before ovulation that varies, because the second part (luteal phase) is pretty much always 14 days.  However, that doesn’t help much since you don’t know exactly when you implanted.

What most doctors will do, especially if a woman has irregular cycles, is do an early ultrasound for dating purposes.  If the early ultrasound confirms your due date within a week of the due date by LMP, then you stick with LMP.  But again, if you’re irregular, they’ll probably just go with the ultrasound due date.  Generally a dating ultrasound is done around 8-10 weeks.

Congratulations!  I’m sure it’ll all get figured out, it’ll just rely on the ultrasound.  The earliest a test will be positive is about 10-14 days after conception, which is “supposed” to be two weeks after your last period started.  So from when the test turned positive, you could guestimate that you’re about 3 1/2-4 weeks pregnant by gestational age.  Good luck!

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