Vedic astrology is very complex as small small parameters together give rise to a prediction. It’s like many different flowers ( parameters ) woven together to make a garland ( final prediction ).

Lets understand how any event takes place with an example of marriage.

1 Marriage will happen when it is promised in the horoscope and mahadasha also signify the same in its ruling period on that time.

2 Marriage will not happen if is not promised in the horoscope but mahadasha signify the same in its ruling period on that time.

3 Marriage will not happen when it is promised in the horoscope BUT mahadasha doesn’t signify the same in its ruling period on that time.

4 Marriage will not happen when it is not promised in the horoscope and mahadasha also do not signify the same in its ruling period on that time.

So from the above dictum it is understood that an event will occur only when it is promised in the horoscope, supported by the ruling mahadasha period of that time.

The same dictum is also applied to the child birth and so if the mahadasha is not supporting the child birth then it will affect a person's ability to have children during that mahadasha ruling period.

There is a catch here and that is a person is not denied of having children and if he is with in the age to have children then he can have children in the upcoming mahadasha if that ruling period support child birth in its agenda.