As far as I am aware, the protein needs for a mother who is pregnant are +30
grams per day.  For breastfeeding, the needs are +20 grams per day.  That is
a whopping 50 grams per day, easily consumed by eating an additional 7 ounces
of lean meat, fish or  other protein.  Of course that assumes that she is
only eating the required 44 gm protein per day for an adult woman.  When I
plan 1200 cal diets, most people get at least 60-70 grams protein per day and
that is not even trying to boost it.  90 grams protein, total,  is very easy
to get in the American diet.  Furthermore, since roughly 50% of protein needs
are met daily from shed cells inside the GI tract, a mother would have to be
very deficient to fail to meet her needs.  The most important thing in
meeting protein needs is to get adequate non-protein calories so that protein
can be used for anabolism rather than burned as fuel.
The "adequate diet" that WIC uses as a measuring stick (4 servings milk, 6 oz
meat, 6 servings grain, 5 servings fruit & veg) provides 100 grams of
protein!!

Sounds like one more case of  "When in doubt, make it up."

Martha Brower RD LD IBCLC (queen of nutrition trivia)