Just because a swallow comes into the house to make a nest doesn't mean adding Ding. We should know that it is normal for swallows to build nests. They will deliberately choose a dark corner that can shelter from the wind and rain, and the eaves at home just meet this standard.
Therefore, swallows will choose a roof to nest. This is a very common thing, it doesn't need too much surprise or speculation, and it doesn't mean that there will be more children at home. However, in some folk customs, it is indeed an auspicious thing to think that swallows enter the house.