I haven't heard of it personally but this is what I found regarding the name of the medication :
Duphastone is the brand name given to it by the company. The name of the medicine is a hormone called dydrogesterone (progesterone). This product is indicated in women trying to conceive if there is proven, documented deficiency of the progesterone hormone (during luteal phase). Once conception has taken place, progesterone hormone is indicated only in pregnanices due to assisted reproductive techniques such as IVF etc. or in cases of habitual abortion (repeated miscarriages). Misuse and overuse of progesterone can lead to a number of side effects including fetal death and spontaneous abortion (more so in the first three months of gestation), musculanisation of female fetus (such as unwanted hair on face), birth defects in babies such as cleft palate and heart defects. Therefore in the United States, the use of this progesterone during "known or suspected pregnancy" is banned. During pregnancy, one should take the most minimal mandatory medicines such as folic acid 5mg daily (such as Folet). If there is anaemia, then one should take an iron preparation along with folic acid (such as Probofex), one capsule a day.
I assume your wife is on this because she does not produce enough progesterone to help a "healthy" pregnancy? Or you had IVF or suffered multiple misscarriages? (I only say that by going from the information above) it also states this medicine is banned in the US due to the unknown side affects it could have on the baby. However I don't know if you are from the UK & if this is okay to use here. I assume your doctor would not prescribe something that would affect your baby; did they mention birth defects if this medicine was taken??
Maybe another lady who takes medication for progesterone can help more but by going from the information I found personally I wouldn't take this. I would read the information booklet & see what it says regarding pregnant women. I would also book another appointment with your doctor & ask them to explain why this medicine is banned in some counties due to birth defects but has been prescribed to your wife.
Please do not panic or worry though I am not a doctor I am purely going from the information I found above.
I hope everything turns out okay for you both.
xx