My 3-month-old daughter is constipated and I thought about the fact that I changed her nipples since she turned 3 months and since then she has been drinking much better. Is this normal?

It is possible that changing the bottle nipples could have affected your baby's digestion and caused constipation. If you noticed changes in her bowel movements since then, it may be worth considering switching back to her old nipples. Additionally, continue giving her the laxative prescribed and monitor her progress over the next few weeks. If there are no improvements, it is advisable to consult a doctor for further evaluation.