It is not recommended to undergo this type of procedure during pregnancy. It is not likely to affect your baby, however, we always suggest waiting until after you deliver.
As a general rule, injectables should not be performed during pregnancy. There are little to no studies on the safety of such procedures during pregnancy which is why it is not recommended. You can consult with your OB-GYN on this, but I find it highly unlikely an injection specialist would perform the treatment until after you deliver.
Best of luck!
During pregnancy it is not recommended to have this treatment, since the filler contains lidocaine, a drug, and your hormonal situation could evoke abnormal responses to the implant. By the way your hormonal situation will help your lips to be plumped up naturally
While an uneventful lip injection with hyaluronic acid should not affect your baby, I would wait until you've delivered before undergoing any medically unnecessary procedures. There is always a risk for complications, which are difficult to treat while pregnant. While rare, these include infection and necrosis. I wouldn't risk it, especially during the first trimester, when your baby is still forming.