is 27 weeks third trimester or is it 28 weeks?

Lizzy โ€ข I'm a first time mom to my handsome little boy who was born 8.26.17๐Ÿ’™ he makes me incredibly happy. follow our journey and I'll follow yours!๐Ÿ˜˜๐Ÿ™‚
I'm 27 weeks tomorrow ๐Ÿ’™๐Ÿ’™ ftm