Not true about red degeneration of myomas is:
Let us see each option one by one.
Red degeneration of fibroid commonly occurs during pregnancy. (Option "a" is thus correct)

The pathogenesis of fibroid is obscure but the initial change appears to be one of subacute necrosis which is presumably due to an interference with its blood supply. Some say that arterial or venous thrombosis is the basis of this and the lesion is the result of infarction. (Option "c" is thus correct).                                                                       
Red degeneration should be managed conservatively with bed rest and analgesics to relieve the pain. (option "d" is thus correct)
There is no need for surgical intervention.
It occurs commonly during pregnancy
Immediate surgical intervention is needed
Due to interference with blood supply
Treated with analgesics
Immediate surgical intervention is needed