This is not true. The commonest birth defects (cystic fibrosis, sickle cell, Tay-Sachs, and so forth) are caused by having two copies of a recessive gene. The reason that these recessive genes are comparatively common is that they confer resistance to diseases (cystic fibrosis - cholera, sickle-cell - malaria, Tay-Sachs - TB).
More specifically, if you have one normal hemoglobin gene, and also the recessive sickle cell gene, you have no symptoms at all, but are able to resist malaria better than if you were homozygous for normal hempglobin.
This partially explains their distribution in different populations.
The non-beneficial, non-neutral mutations are most often called 'miscarriages'
Now both of us have explained this. Odds?