When does the first trimester end?

Valerie Padron · July 2009

At the beginning of Week 12 (as in, "today my ticker says 12 weeks") or the first day of Week 13?

kimandjared · July 2009

On the bump it ends 13 weeks 3 days....

murfygirl · July 2009

I could be wrong, but I think week 12 is considered part of your first tri. I don't think you're officially in your 2nd tri till week 13. I am so ready to be done with my first tri, barfing is getting over rated and I think someone stole my energy!

shindylahoe · July 2009

kimandjared:
On the bump it ends 13 weeks 3 days....

that seems so random!

SkiGirl1080s · July 2009

Ditto Kim. Since the pregnancy lasts 40 weeks, you divide by three and end up at 13w, 3d. Most books say first trimester starts at the 12th week though.

murfygirl · July 2009

kimandjared:
On the bump it ends 13 weeks 3 days....

Is the 3 days just for good measure? Kinda weird that they add 3 days in there!

mushmouseKD · July 2009

I was wondering this, too, because I always thought of each trimester as 3 months- making up 9 months. But since they start counting on the 1st day of your last cycle and you're not really pg for the 1st 2 weeks, is the 1st trimester shorter than the others? Or do they average it out over the full 40 weeks?

rapst1 · July 2009

I agree with PP that it does end at 13 w 3 d, but I think after 12 w you can breathe alittle easier. My Dr told me that the chance of a m/c after 12w drops to below 1%. so, to me, that was a bigger step then when I will reach the 2nd tri this Friday!

krystal0707 · July 2009

My thinking is when you are actually 13 weeks pregnant. So, they day after 12 weeks 6 days!

Please correct me if I am mistaken. I just love how every different resource you use gives you different information. Confused

nlvaden · July 2009

kimandjared:
On the bump it ends 13 weeks 3 days....

This

Valerie Padron · July 2009

rapst1:
I agree with PP that it does end at 13 w 3 d, but I think after 12 w you can breathe alittle easier. My Dr told me that the chance of a m/c after 12w drops to below 1%. so, to me, that was a bigger step then when I will reach the 2nd tri this Friday!

uuuuu I like that statistic!

hockeypirate · July 2009

My OB considers 2nd tri to start at 12 weeks and I'm going with that.

murfygirl · July 2009

I have an appointment with my midwife next thurs and I will be exactly 12 weeks and at my 7 week appointment she said next time I see you you'll be done with your first tri, but I did notice on here most people don't change boards till well into their 13th week. I am still going with my midwife she spent 9 years in school the bump didn't.

92405bride · July 2009

well, my iPhone iPregnancy app told me yesterday that my 2nd trimester started, so I'm going with that

I think the rule is 12 weeks is the end of the developmental 1st trimester, and 13 weeks 3 days is just 40 weeks divided by 3.

jill_aitoro7 · July 2009

I think there's some misinterpretations of 12 weeks, which is causing the confusion. Your first trimester lasts for 12 weeks (or 12 weeks and a few days if you want to be technical). But that means when you COMPLETE your 12th week, not when you first hit it. So, technically, your ticker would say 13 weeks (as in, you just hit your 13th week, and completed your 12th) at the start of your second trimester.

jill_aitoro7 · July 2009

Here's a cool web site actually that gives you trimester stages by development, gestation and conception. (not really sure what gestation means).

https://www.ivf.ca/duedate.php

Anna&Matt · July 2009

My OB congratulated me on making it through 1st tri this morning at 12 wks but in my head it's not 2nd tri until 13w3d.

But he said our risk of m/c is less than 1% based on the growth rates they've seen on u/s and our NT measurements unless something really abnormal comes back with the NT bloodwork.

Valerie Padron · July 2009

Actually... when the ticker starts it does not start at week 1.. it starts at 0 week, 1 day. So by the time it displays 1 week, a full week has elapsed. So wouldn't 12 weeks have elapsed by the time it says 12 weeks?

jill_aitoro7 · July 2009

valandrob:
Actually... when the ticker starts it does not start at week 1.. it starts at 0 week, 1 day. So by the time it displays 1 week, a full week has elapsed. So wouldn't 12 weeks have elapsed by the time it says 12 weeks?

Oh! I didnt know it did that - if so, then ya, I would think you've completed 12 weeks by the time the ticker says 12.

Brooke_Lilly'smom · July 2009

Yep, when you hit 12 weeks you are actually 12 weeks, then 12 weeks and 1 day, so working on week 13.

GoodyWife06 · July 2009

At my last appt (11wk3dy), I asked my dr. when he considered the end of 1st tri to be. He said, "Oh, somewhere around the end of this week," which would have been at 12 weeks. But still, in my mind I won't be out of 1st tri until I hit 13 weeks on Satuday.

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