I have been slightly confused about when exactly the third trimester begins. I had read that the second trimester ends at week 27 and the third trimester begins at week 28. Today I am 26 weeks and got notifications from two of my <a href="https://play.google.com/store/apps/details?id=com.glow.android.nurture">pregnancy apps</a> one being Glow that said congrats on starting your third trimester. So I know it's only a difference of a few weeks but can someone please tell me am I in my third trimester now at 26 weeks or not until 28?