Sudden infant death syndrome practice

At the six-week check, the mother of a healthy breastfed girl says she is so tired that for the second half of most nights she brings the baby into her own bed. Nobody in the household smokes or vapes. Otherwise the baby sleeps in a bassinet beside the parents' bed, on her back, on a firm mattress with a fitted sheet and a light blanket tucked below her shoulders. She is thriving. Which one of the following pieces of advice is most likely to reduce this baby's risk of sudden unexpected death in infancy?