Why should aspirin not be coated when taken during pregnancy?

The reason why aspirin should not be coated when taken during pregnancy is because uncoated, chewable aspirin is used for the prevention of pre-eclampsia. Studies have shown that taking it at bedtime may have slight advantages for this purpose compared to taking it in the morning, as it may help stabilize circulation better. In addition, the chewable formulation is preferred because the released dose may be slightly larger and especially faster than in the coated formulation.