In his The Dilemmas of Laissez Faire Population Policy in Capitalist Societies: When the Invisible Hand Controls Population (as all Linder's invaluable Greenwood books, this one sells for well over $50), Marc Linder takes up this question in the chapter "Was Marx a Cyrpto Malthusian:
"It was not the case that Marx believed that small proletarian families would eliminate capitalist proverty or the proletariat for that matter; nor washe of the opinion that the correctness of Malthus's population theory and the availability of contraceptive methods had to be withheld from the working class lest its class consciousness be jeopardized. On the contrrary: the whole thrust of Marx's theory of the industrial reserve army was that the process of capital accumulation was relatively immune to the problem of 'natural' underpopulation because it had its own methods for creating surplus labor, which reinstated the proletarian condition regardless of the size of working class familiies."
At the same time, Linder recognizes confusions and problems in Marx's population theory, e.g., "A contentious theoretical question arises here as towhether Marx's alleged proclivity to take population growth for granted fatally undermines his claim that the processes sustaining the capitalist reserve army of the unemployed operate indepedently of absolute increases in population."
And he considers the charge that "Marx was committed to an 'implicit Malthusian theory of population,' which blinded him to the 'fact of mass progress..[which]made men rethinkthe calculus of having children' by means of a non Malthusian check on the birth rate."
And in full agreement with Brad and Barkley, David Harvey has written, as quoted by Linder: "When it comes to features promoting a high rate of birth (early age marriages, rising birth rates, etc) Marx does not read very differently from Malthus...Marx seems to be trapped in the same general swamp of ignorance with respect to the process of reproduction of labor power as were his contemporaries."
best, rakesh
ps a couple of works on demography intended for general discussion recently published include WW Rostow, THe Great Population Spike and Michael Teitelbaum A Question of Numbers.