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The commercial versions of the growth factor‐supplemented media are based on the formulation provided by Chang et al.^{652, 653} The classic “Chang medium” included transferrin, selenium, insulin, tri‐iodothyronine, glucagon, fibroblast growth factor, hydrocortisone, testosterone, estradiol, and progesterone. These factors are added to a 1 : 1 mixture of Dulbecco's modified Eagles' medium (DMEM) and Ham's F12 medium, plus sodium bicarbonate, and small amounts of HEPES buffer and antibiotics. Chang et al. pointed out that their preferred basic medium mixture can be replaced by a number of other formulae (e.g. Ham's F10 or F12, Coon's modified Ham's F12, McCoy's 5A, RPMI 1640, DMEM, minimal essential medium and TC 199) without detriment. Chang and AmnioMAX media that differ in their buffering systems are available for use in closed or open cell culture systems. As with other aspects of the cell culture art and science, local preferences vary with respect to choice of specialized media, fetal or newborn bovine serum, and whether to mix these media with less costly media.^{609, 633, 634, 653, 654}

It is assumed that the various peptides, hormones, and trace elements act synergistically on the recruitment of cells into the cycle and keep them from reverting to the G₀ stage after completed division. A greater number of cells within a colony will therefore stay in the proliferative pool. The cycle time of individual cells, with the possible exception of the duration of the G₁ phase, is not likely to change. Unless Claussen's micropipette method⁶⁵⁵ is used, a culture period of 5–7 days will thus remain the minimum time requirement for prenatal cytogenetic diagnosis employing AFC cultures. In our laboratory, we experimented with 12‐hour Colcemid exposure and very early harvests. We obtained a small number of metaphase cells after 3 and even 2 days in cell culture but the number of metaphases was insufficient for a complete analysis.

A drawback noted by some users of Chang and AmnioMAX media – other than the expense – is their limited shelf‐life. Lyophilized or other, more stable media supplements are offered by some manufacturers (e.g. Condimed, UltroSer) but cloning efficiency testing so far has failed to identify a commercial product that consistently yields higher cloning efficiencies than fresh lots of Chang media.⁶⁰⁴ Use of Chang‐type media may augment the incidence of chromosome breakage and chromosomal mosaicism in AFC cultures but rarely to the extent that the cytogenetic interpretation is compromised.^656–659 This may in part result from the fact that Chang media can facilitate the growth of E‐type colonies and these colonies yield higher rates of random chromosome changes.^{588, 611} However, the advantages gained by the reduction of turnaround time and the substantial decrease of culture failures using Chang‐type media appear to outweigh the potential drawbacks of increased chromosomal breakage and pseudomosaicism.