I have no idea if it's like this for everyone, but I just... knew. I think the BH I had were not really painful. The actual CX, even though they started off mild, were. For me, they were also located differently. I felt my BH in the front and my CX in the back.
I was told a real contraction will take your breath away and you won't be able to talk through it. When they get like that, it's when you should start timing them.
I've been having BH. I don't feel the contraction, except I do feel pressure on my bladder and then feel my abdomen and its hard.... voila BH! "Real" contractions are different in that they cause changes to the cervix. I have been told that real contractions feel like intense mentrual cramps. Idk if that helps. I could give better answers in a couple of months :-)
Don't count on pain as a measure of us a contraction is "real" or not. With both my kids, my contractions didn't hurt until about 2 hrs before they were born. I could still talk through them at 7cm.
Real contractions are consistent and do not go away. If you have BH they can be uncomfortable for a bit but changing your activity can make them go away. When it's real it won't matter what you do they will keep coming closer together.
I know it's infuriating to hear "you'll know" but if you are not sure then consider it BH.
What all PPs have said. BH are more of a "tightening" where contractions (for me) are more like intense menstrual cramps. I was pretty sure I could tell the difference (FTM) and then after a trip to L&D and hooked up to the monitors, it confirmed what I was feeling. Ive been having them for a few weeks now, currently 38+3 and they get more intense. Im able to time them. They will be about 5 mins apart, to 3 mins apart and much more intense. But for me this goes on a few hours and then subsides. OB checked me yesterday and stripped my membranes, said I was 2cm and 80% effaced so Im definitely close. At this point, I time the contractions and if they continue for more than a few hours or if I leak fluid or they grow so intense I cant talk thru them, then I will head to L&D! I think you will certainly KNOW the difference but I was also very unsure like you til the monitors confirmed what I was feeling.
Real contractions made me want to move. Compulsively, I just felt the desire to walk through them. I didn't count them as real until I had a hard time sitting still & laying down wasn't happening. I just knew.
For me, the real ones started off just annoying and then gradually got worse. I knew it was the real deal or something else was very wrong with me because the pain was pretty bad.
~after 34 cycles we finally got our 2nd little bundle of joy~
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I could breathe/talk through all my CXs until I was 7/8 cm dilated. I had back labor so it was totally different than menstral cramps. Pay attention to timing. If they start coming every 5-7 minutes and last over a minute, start timing. You MAY be in labor.
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I have to agree with everyone who said that pain is not a measure of whether they are "real" or not. I timed contractions with my son for over 3 hours (and they were regular and went from 5min apart to 2-3 min apart), and they didn't feel much different than the BH I had been getting for weeks before that. With my daughter they became so painful I cried through them until I begged for the epidural. My son was an RCS (went into labor early), so I'm not sure how they would have progressed if I had done a VBAC.
Re: Braxton Hicks compared to the REAL thing
"Real" contractions are different in that they cause changes to the cervix.
I have been told that real contractions feel like intense mentrual cramps.
Idk if that helps. I could give better answers in a couple of months :-)
I know it's infuriating to hear "you'll know" but if you are not sure then consider it BH.
That's really it.
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BH are just annoying and uncomfortable.
For me, the real ones started off just annoying and then gradually got worse. I knew it was the real deal or something else was very wrong with me because the pain was pretty bad.
~after 34 cycles we finally got our 2nd little bundle of joy~

My IF blog
LFAF Summer 2016 Awards: