Ruling on Making up missed prayer that was missed willingly because of not enough courage to take major ablution at night?

Most of the newly married couples in the subcontinent of ours don't offer their Fajr prayer at masjid willingly on time! They make it up at the time of Zuhr prayer as 'Kada'(making up missed prayer). They involved in intercourse and they don't want to take their bath(major ablution) at the middle of the night out of feeling shy or may be for the fear of cold water or laziness, I don’t know why they do so, but what they is that they willingly missed the Fajr prayer with the intention of making it up with the next prayer. So my question is, If someone willingly miss any prayer, is there any ruling on making it up later on?