At how many weeks can doctors detect deformations and disorders with the fetus during pregnancy?

12-24 weeks: Depending on the skill of the observer, many fetal abnormalities can be seen between 12 and 14 weeks. Optimal detection of anomalies requires an exam between 16 and 20 weeks, and the heart is best seen around 24 weeks. Genetic problems can be diagnosed with chorionic villus sampling at 10-12 weeks. Many fetal problems cannot be diagnosed at all before birth, however, even in the best centers.