Is it obligatory for a woman to stop breastfeeding her child if she becomes pregnant with another, and how can she complete two full years of breastfeeding in this situation?

If a woman becomes pregnant while she is breastfeeding, this is called 'ghilah,' and it is permissible in Islamic law, based on the Prophet's (peace be upon him) saying: "I had intended to forbid ghilah, until I remembered that the Romans and Persians do that, and it does not harm their children." So, if it does not harm the nursing infant, then the pregnant woman may breastfeed her child for two full years.