Molybdenum appears to be a natural constituent of cows’ milk, the amount varying in different individuals but of the general order of 40 to 70 γ per liter of whole milk.http://www.journalofdairyscience.org/article/S0022-0302(51)91818-8/abstract
Feeding 500 mg. daily of ammonium molybdate to eight cows for periods of 2 mo. increased the average amount of molybdenum in their milk about fivefold.
The level of molybdenum in these milks was higher than that of manganese and much higher than the level of cobalt. The response to feeding a supplement of the element, as indicated by increased levels in the milk, was greater than for any other trace element studied thus far.
Milk samples from control cows milked directly into glass showed similar levels of molybdenum as those obtained via the milking machine, thus eliminating the possibility that any of the molybdenum in the milks was due to metallic contamination.
Analysis of composite samples of cream and skimmilk showed that most of the molybdenum in “control” milks or in those from cows receiving a molybdenum supplement was concentrated in the cream fraction.
So skim milk, nonfat yogurt, and ice milk are not going to be particularly good sources of molybdenum. Unfortunately, the slow stomach of a pregnant woman often doesn't respond well to large amounts of fatty food. Plus, some women experience aversion to milk during pregnancy.
So the answer to the question above seems to be that cream is a good source of dietary molybdenum if you can handle the smell and taste and keep it down afterward.