Glyn Rostron, 38, and Michelle Duffy, 32, both pleaded guilty to child cruelty when they failed to seek help immediately when their five-week-old son's arm was broken in two places.
"One of you had caused that injury and the two of you put your own interests ahead of that of your son"
However, as the court could not prove which parent broke the little boy's arm in the first place, they were sentenced to just five months in prison each - a sentence which has been suspended for 18 months.
Judge Clayson told the couple: "One of you had caused that injury and the two of you put your own interests ahead of that of your son.
"That is an attitude which is abhorrent to all right minded people."
The little boy's injury was revealed when, on 1st December 2013, the pair took him to A&E at Royal Bolton Hospital.
They then told doctors that the child, known as TJ, had not been moving his right arm for a couple of days.
X-rays revealed both bones in his lower arm were broken and doctors concluded the injury could not have happened accidentally.
The little boy, and a second child, were taken into care last year - and a defence lawyer revealed that Duffy is now considering sterilisation.
The judge added: "You will no longer have the pleasure of bringing up not only your young son but also the other child. That is serious punishment indeed."
As well as the suspended sentence, the couple were also handed a supervision order for six months and ordered to each pay £400 prosecution costs and a £100 victim surcharge.