My basic understanding of trimesters are:

First Trimester, first to third months, 1st to 13th weeks
Second Trimester, fourth to sixth months, 14th to 26th weeks
Third Trimester, seventh to ninth months, 27th to 40th weeks

So if the patient goes into labor with delivery on her 35th week, I would use O62.14 Preterm labor third trimester with preterm delivery third trimester?

What I’m not understanding is the description repeating the trimester.

Example:
O62.12 Preterm labor second trimester with preterm delivery second trimester
O62.13 Preterm labor second trimester with preterm delivery third trimester
O62.14 Preterm labor third trimester with preterm delivery third trimester

Please help!

Thank you in advance!

Marissa