What is the ruling of the Islamic Sharia regarding a mother's supplication against her married daughter for her not to conceive from her husband, and is it possible that Allah has answered her prayer?

The supplication of parents for their children is answered. A delay in pregnancy might be due to the mother's supplication (dua). Therefore, it is advisable to be dutiful to her and exert effort in pleasing her, including seeking the mediation of the father, relatives, and anyone who has influence with her.