I had a litter of preemies this year. I don't think that being premature will affect pattern. I think that temps is what "most likely" will affect pattern.
My theory is.... When you have a mixed litter of preemies and full term babies, "some" of the babies didn't get enough heat to mature properly. So, these babies that are premature had fluctuating temps during gestation. This "could" result in a funky pattern.
Now if you have an entire litter of preemies, which is what I had, I think none of them had those good temps to properly develope.
My female had really good days, where she maintained body temps of 87 to 91. Then she had other days, where she was 82 to 86. So, I know my female didn't properly regulate temps. This resulted in an entire litter of preemies. Now, "most" of these babies had a fairly normal pattern. I had one that was "extremely small". It was about 6 inches long and had "no pattern". It was just that far premature and it's pattern wasn't set yet. I have another one that has a "zig zag" pattern. It was the most developed of the litter.
Out of 20 babies, I only have 5 left alive. Fortunately, one has already shed and eaten. A second one has shed, but it hasn't eaten yet. I have 3 left that still need to shed and eat. These are "very small" babies, but fully developed.
That's why I think it's temps that "could" affect patterns. Improper temps could also cause them to be premature. It's just a theory and I could be wrong, but I have noticed that preemies tend to have patterns that are "different". Of course, they can also have patterns that are "normal". I've seen both.