Knitting a heart: knit & purl, intarsia or loop.
If you knit in 1 colour, you can you use the blanket on both sides.

For a baby blanket knit the first rows in garter stitch and the first 5 stitches of every row: 1 edge st, 4 garter st. (so that the blanket will not roll)

If you knit a baby blanket with other yarn, know what size you want and calculate with the pattern (chart).