A new baby born at before complete nine month. the baby will have any defect?

Not necessarily, but it could be "at risk for numerous medical problems affecting different organ systems".

"In humans, preterm birth refers to the birth of a baby of less than 37 weeks gestational age. Premature birth, commonly used as a synonym for preterm birth, refers to the birth of a premature infant. Because it is by far the most common cause of prematurity, preterm birth is the major cause of neonatal mortality in developed countries. Premature infants are at greater risk for short and long term complications, including disabilities and impediments in growth and mental development. Significant progress has been made in the care of premature infants, but not in reducing the prevalence of preterm birth."

"In humans, whereas the usual definition of preterm birth is birth before 37 weeks gestation, a "premature" infant is one that has not yet reached the level of fetal development that generally allows life outside the womb. In the normal human fetus, several organ systems mature between 34 and 37 weeks, and the fetus reaches adequate maturity by the end of this period. One of the main organs greatly affected by premature birth is the lungs. The lungs are one of the last organs to develop in the womb; because of this, preemies typically spend the first days/weeks of their life on a ventilator. Therefore, a significant overlap exists between preterm birth and prematurity: generally, preterm babies are premature and term babies are mature. Prematurity can be reduced to a small extent by using drugs to accelerate maturation of the fetus, and to a greater extent by preventing preterm birth."
Source and further information:
http://en.wikipedia.org/wiki/Preterm_birth

That depends on how long before the 9 months the baby is born, and why.

Premature babies have a much more difficult time surviving outside of the mother's womb - and the more premature they are, the more difficult it will be for them to survive.

As for birth *defects* I am wondering whether or not you mean congenital ones that would also cause a premature birth?

After seven months the odds of survival increase.

i have a brother he was 6 weeks premature ,never anything wrong with him ,but that does not mean there will not be problems it is a part of birth at times can be unpredictable.

Not necessarily, but there is a slightly greater risk of a birth defect when the baby is born prematurely.