I am in my second month of pregnancy and my gynecologist advised me to refrain from fasting Ramadan. To my knowledge, a pregnant woman has the dispensation to refrain from fasting the month of Ramadan. Allah the Almighty has made it possible for me to make expiation of feeding 30 poor people for the 30 days I will refrain from fasting.
My question is: Is it obligatory for me to make up these fast days after giving birth? Please note that I intend to breastfeed my child if possible, and it is not recommended to fast during the nursing period. I am due to give birth next May by the will of Allah and the upcoming Ramadan will coincide with the weaning period.
Please give me a definite answer on whether it suffices to feed 30 needy persons or if it is necessary to make up the fast days. If necessary, how and when do I to make them up?

As long as a specialized physician has advised you against fasting on account of your pregnancy, then you may follow her recommendation. However, you must make up the unperformed fast days after Ramadan; expiation alone is not sufficient if you are able to fast after giving birth. It is not necessary to make up the missed fast days immediately after Ramadan; its time is extendable i.e. you can make them up at any time. It has been authentically reported that 'A`isha (may Allah be pleased with her) used to make up her unperformed fast days of Ramadan in the month of Sha'ban. If she delayed making them up until the next Ramadan, she would fast the current Ramadan and make up her unperformed fast days afterwards. She would not make expiation if her delay was due to an excuse, otherwise she would make expiation in addition to making up her unperformed fast days.

The ruling
The inquirer whose physician advised against fasting must make up her unperformed fast days whenever it becomes possible for her, whether or not she makes them up consecutively. The expiation she made does not discharge her of the obligation of making up the unperformed fast days due to the words of Allah Almighty Who says,The prescribed number (should be made up) from days later. [Al-Baqarah: 184]

This is because she can fast on other days and because her unperformed fast days are a debt owed to Allah; a debt owed to Allah has more right to be fulfilled.

Allah Almighty knows best.