All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is a difference of opinion among the scholars regarding the pregnant woman who breaks fasting during Ramadan. We adopt the opinion of Ash-Shaafi‘i and Ahmad that if she breaks fasting in fear for herself or for herself as well as the fetus, then she is required only to make up for the days of fasting that she missed. However, if she breaks fasting in fear for the fetus only, then she is required to make up for the days of fasting along with giving an expiation of feeding a poor person for each day from the money of the fetus's guardian; this is the most prudent opinion.
The opinion that she is required only to make up for the days of fasting is based on analogy, because the pregnant woman is like the sick person whose recovery is expected.
There is a third opinion on this issue, which is the one which you used to apply, namely, that she is required to give the expiation only. According to this opinion, she is not required to make up for the days of fasting. This opinion is also strong because it was adopted by two great scholars from among the Companions: Ibn ‘Abbaas and Ibn ‘Umar . Al-Albaani indicated in his book "Al-Irwaa’" that this opinion was traced back to them through authentic chains of narrators.
Nevertheless, now that you believe that this opinion is outweighed, we believe that your wife is required to make up for the days of fasting that she missed.
Allah Knows best.