Welcome to HCM
Read your prob, youe wife has oligohydroamnios means the liqur in which fetus lies is less then proper amount. but now she is 6month of pregnancy
so there is more chance to formation of liqur , so do not worry start treatment as per advised. for it you should get high resolution (3D) sonography
for confirming it. at 24th wk of pregnancy there is no need to worry as it is curable.if it persist later on pregnancy then it produse congenital abnormalities in fetus.