The most effective step in MCH is
The objectives of MCH care are-

Reduction of morbidity and mortality rates of mothers  and children 
Promotion of reproductive health
Promotion of the physical and psychological development of child within family 

This is achieved by working under the following sub components- 

Maternal health 
Family planning
Child health 
School health 
Handicapped children 
Care of children in special settings such as day care centres

It is evident from the objectives and Sub components that the most effective step is maternal health promotion .
Factors that effect maternal health such as urbanisation , rural migration , changing patterns of women's work and status is seen to have direct effect on child bearing and child rearing. Thus by achieving maternal health,it is possible to assure the achievement of all other steps. Hence option 1 is the most appropriate answer.
Maternal health promotion
Child health promotion
School health promotion
Non formal education of the mother