Rashi on Genesis
לא שכלו means HAVE NOT MISCARRIED — Similar are: (Hosea 9:14) ‘‘a miscarrying (משכיל) womb”; (Job 21:10) “his cow calveth and casteth (תשכל) not her calf”.
Rashbam on Genesis
לא שכלו, neither because of any lack of adequate grazing nor due to careless supervision
Sforno on Genesis
רחליך ועזיך לא שכלו, you have found me as possessing the very reverse of the characteristics of a thief. Not only did I serve you faithfully, but I have treated you even better than fairness dictates. I have endeavoured with all my skill to prevent your sheep from giving birth to premature, and stillborn young.