Baby played 168 deliveries and struck six boundaries en route to his fifty and also shared unconquered 57 runs with VA Jagadeesh (24 not out) for the fifth wicket as Kerala played out 73 overs in the day.
Wicket-keeper Sanju Samson (47) also played a good hand with the help of seven fours and one hit over the fence.
However, Kerala did not have the best of starts after being invited to bat as they lost both their openers -- Jalaj Saxena (2) and Bhavin Thakkar (14) with the scoreboard reading 17.
Thereafter, Samson and Baby stitched 57 runs for the fourth wicket to stabilise Kerala's innings before the former edged a Rishi Dhawan delivery to wicket-keeper Ankush Bains just three runs short of his half-century.
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For Himachal Pradesh, Gurvinder Singh (1/17), Shresth Nirmohi (1/29) and Dhawan picked up a wicket each.
Brief Scores:
Kerala: 163 for four in 73 overs (Sachin Baby 52 not out, Sanju Samson 47; Gurvinder Singh 1/17).