Certainly God is doing something:
Psalm 139:13-14 13 For you created my inmost being; you knit me together in my mother's womb
This also brings some perspective on the abortion debate, should we murder an unborn child just because they have a deformity or disease? Although it is not a black and white issue, the answer should generally be "no".
After we are saved, we still retain our DNA, our personality, and our traits. But over time God changes these and whether it is by changing our hormones, DNA, or what.
Studies of identical twins separated at birth has shown that DNA can change over a lifetime depending on our choices and our environment. For example if we inherit the DNA of an athlete but we eat fatty foods, and donuts over our lifetime, our genes can change, and our children may be obese.