Is there an effect both positive or negative to the county's economy when couples have plenty children?
In the past before the current economic era, around the 15th century and the beginning of the French industrial revolution, having many children was seen as fertility and good for both the family work force and country's also. The labour force was majorly manual and those who worked at the plantations were sort after as able bodied men or women.
But at the moment, what is the viability of having many children especially as it could reduce the per capital income.
It has a positive and negative effect though it doesn't directly affect the economy but connected based on the family's status in this society. For people who belong in upper class, having plenty of children is not a problem since they can afford to give food on the table, a proper education and a decent life to live comfortably. Children from upper class can contribute for the betterment of the economy once they grow up and had a job.
But this is not the case if the family is from poor family (though not all). It's the opposite of what the upper class can give on their children. They will rely on the Government's assistance to help them sustain the needs in general. That's why nowadays it's wise to have a certain number of children based on your capability to give them a comfortable life.