Is it true that giving birth causing back ache later on?

For the short term. The things that happen in the body during pregnancy and shortly thereafter can certainly cause or worsen back pain. This should resolve pretty quickly after birth. If pain persists, a detailed exam can usually determine the cause. Thank you fir your question.
During and after. Giving birth can cause the top of the sacrum to shift forward, leading to pack pain. A do skilled in osteopathic manipulation can likely treat this for you.
Yes. It can but it typically goes away within a few months to a year.

Related Questions

Lower back ache since giving birth 8 years ago as I had contractions in my back, how can I stop it hurting it shouldnt be hurting 8 years after?

You're right. Due to the changes that happen in pregnancy, your posture and spinal alignment can change. Sometimes, if that is not corrected, it can cause long lasting pain. I recommend the exercises that can be found in robin mckenzie's book, fix your own back. If that does not help, a good osteopathic medical doctor who specializes in gentle manipulation can help improve your spinal alignment and back pain.