[Colonists] tend to marry early, have a full quota of babies, [put them in cryogenic suspension,] then rear them later, as money and time permit. It reconciles that discrepancy, so increasingly and glaringly evident since the Terran Industrial Revolution, between the best biological age for having children and the best social age for supporting and rearing them. - Podkayne of Mars, Robert A. Heinlein, 1963
Most women in need of egg donation have left childbearing too late to use their own--but once eggs can be frozen routinely, young women will surely bank them so they can reproduce when it suits them, not when it suited our shorter-lived ancestors. - "Buying babies, bit by bit", The Economist, 12/23/2006
This didn't see the changes that have happened in marriage patterns since then, but some of his later books addressed that.