mid 19C - middle class women as wet nurses?

From an undated letter from a London boy to his sister a year older
(who was probably with their grandmother, whom she seems to have
visited frequently) in, I guess, 1867, when the writer would have been
9 and a half and the youngest child was born:

"...The baby is so fat and plomp because Mama gives it so much milk.
She has too much she is obliged to have another baby to nurse. I saw
the baby last night for the first time. And also Mama as I had not
seen her since you had gone. ....."

The family was upper middle class.

myths...

That makes more sense than my vision of a doctor having a waiting list
of respectable underfed babies ready to be brought along for a relief
feed.

Thank you Eve, and others who have commented.

Was it normal for a baby to be prescibed to relieve the problem of
excessive milk production, or is it more likely the boy misunderstood
remarks made by the adults around him?

C Rihan...

I don't know, but it seems an unlikely remedy to me, so why would she
have had another baby there?
Could she be babysitting for a friend? Or was the baby's mother too
ill to nurse it ?
Or could she have had twins, but the doctor advised her that one
wouldn't live long, so she'd only told the children about the heathy one
and then had to explain to her son why there was another baby there?
Or perhaps the adults were just joking that the mother had so much milk
that she'd have to take in another baby to nurse, and there was no other
baby.

I'm thinking that the last isuggestion is the most likely explanation.

Best wishes
C.Rihan

andrew...

Multi-suckling herds of cattle were, at one time, common to rear calves
for the beef trade. Wet nursing was, of course, common amongst all
classes of society but, not having much knowledge of lactating humans,
we might ask for help from someone having relevant experience, maybe a
midwife? I suspect a youthful misunderstanding.

Yours Aye Andrew Sellon