Is the phrase "congenital birth defect" redundant?

con-gen-i-tal: (m-w.com)

1. existing at or dating from birth [congenital deafness]
2. acquired during development in the uterus and not through heredity [congenital syphilis]

I ran across the phrase congenital birth defect in a paper, and given the definition above it seems to be redundant.

Yet a simple google search reveals a wide number of uses. Can anyone provide an authoritative explanation about this?

After some research, I believe the answer is yes. Congenital anomalies (or congenital defects) are, inherently present at birth. The World Health Organization's first 'key fact' about congenital anomalies states:

Congenital anomalies (also referred as birth defects) affect approximately 1 in 33 infants and result in approximately 3.2 million birth defect-related disabilities every year.

Congenital can refer to different mechanisms of causation [Brent and Fawcett 2007][reference]:

the etiology of congenital malformations can be divided into three categories: unknown, genetic, and environ- mental

[reference]: Brent, RL and Fawcett, LB: Developmental toxicology, drugs, and fetal teratogenesis. In Reece EA, Hobbins JC (eds.) Clinical Obstetrics: The Fetus and Mother, 3rd edition, Blackwell Publishing Inc., Malden, MA, Chapter 15, pp. 217-235, 2007.

Here's what Merriam-Webster's Medical Dictionary says about congenital:

1 : existing at or dating from birth (congenital deafness)
2 : acquired during development in the uterus and not through heredity (congenital syphilis) — compare ACQUIRED 2, FAMILIAL, HEREDITARY

and here's what it says about congenital adrenal hyperplasia

any of several hereditary disorders that are marked by inadequate synthesis of cortisol due to an enzyme deficiency determined by a defect in an autosomal recessive gene, that are typically characterized by excessive production of androgens, virilization of female external genitalia, and hypertension, and that include a severe form in which inadequate synthesis of aldosterone results in potentially fatal hyponatremia and hyperkalemia shortly after birth—(abbreviation: CAH)

The usage doesn't always mean hereditary or not hereditary: it can mean either. Some congenital conditions are genetically transmitted (hereditary) and some are caused by developmental problems with exogenous (external, not genetic) causes.