DNA testing of newborns, or even pre-birth, may signal several diseases that the newborn may be susceptible to, but this difficult choice has its drawbacks too...The test will not point to the fact that the parent is not the biological parent (unless the blood grouping is very dissimilar, or show diseases that either parent is unlikely to have inherited.
The main question is: should the test show, that the child is not the biological father's offspring, at a much later date, what recourse would be open to the father? Disinherit the child? Sue the mother for fraud, or abandon the child , and divorce the mother at this late date?
Most new born are routinely given blood tests at birth . Do we want a DNA test added to it?
The emotional and financial cost may be prohibitive in the long run.
Once you accept the child as yours at birth, in my opinion, you fully take on all responsibility for it, and hope and trust your decision.