Is it safe to take phytonadione while pregnant or breastfeeding?

Yes: It is a category c drug which means you can use it if you have a good reason for it.

Generally: Vitamin k may be taken by the mother but it is not a subsitute for giving vit k to the infant usually intramuscularly but may be given by several oral doses. Vit k is important to prevent hemolytic disease of the newborn and needs to be given to the infant. However, mothers may also take this for her own health but is usually not needed if she has a normal gut flora.