How to define a normal or abnormal nuchal translucency measurement can be difficult. The use of a single millimeter cutoff (such as 2.5 or 3.0 mm) is inappropriate because nuchal translucency measurements normally increases with gestational age (by approximately 15 % to 20 % per gestational week from 10 to 13 weeks). At 12 weeks of gestational age, an "average" nuchal thickness of 2.18 mm has been observed; however, up to 13 % of chromosomally normal fetuses present with a nuchal translucency of greater than 2.5 mm. Thus for even greater accuracy of predicting risks, the outcome of the nuchal scan may be combined with the results of simultaneous maternal blood tests. In pregnancies affected by Down syndrome there is a tendency for the levels of human chorionic gonadotropin (hCG) to be increased and pregnancy-associated plasma protein A (PAPP-A) to be decreased.

Answer this question based on the passage: normal range for nuchal fold at 12 weeks? Okie... think carefully first, then make a decision:
To answer the above question, the relevant sentence is: At 12 weeks of gestational age, an "average" nuchal thickness of 2.18 mm has been observed; however, up to 13 % of chromosomally normal fetuses present with a nuchal translucency of greater than 2.5 mm. So, the answer is 2.18 mm.