Parents have many children because few survive
Many children are needed to work the land
Children are a sign of virility
Some religious beliefs and cultural traditions encourage large families
A lower infant mortality rates means less pressure to have children
Increased mechanisation and industrialisation means less need for labour
Increased desire for material possessions and less desire for large families
Emancipation of women
Famine , uncertain food supplies and poor diet
Poor hygiene, no piped clean water or sewage disposal
Improved sanitation and waters supply
Improvements in food production in terms of quality and quantity
Improved transport to move food and doctors
A decrease in child mortality