I know as a parent it is tempting to overlook problems in baby teeth since they fall out eventually. Since the enamel in a baby tooth is thinner than an adult one, the cavity can spread fast. 
If we don’t treat it, the infection could damage other teeth and even invade the body. Baby teeth need to be filled.
Most of the time we can repair cavities with fillings which prevent the spread of infection because we remove decay and replace it with filling material. Removing a tooth too early presents a lack of space retaining in anticipation of the adult tooth. The absence of the tooth can interfere with the child’s speech and eating. Additionally, the early loss may lead to orthodontic problems.
I prefer to fill a child’s tooth before they start experiencing the first signs of possible infections. The tooth can be sensitive to cold and have a twinge while eating hard foods. Either one can progress to a constant ache.
Of course, the best way to avoid cavities is seeing the dentist at the age of 1 to set good habit. The dentist can identify possible pitfalls to a life of good dental health. The primary risk of cavities is the same as with adults; eating sweets, sipping juice and not water, Also, the child needs to develop the habit of brushing twice a day with the last brushing right before bedtime.