Cloth diapers. I suppose diapers are the biggest issue. Cloth diapers seem to be more ecofriendly provided the way they are laundered is also ecofriendly. Breastmilk is also ecofriendly.
Control environment! Look at everything that involves the nursery. Paint the walls with "green" paints that do not emit voc’s (volatile organic compounds), pass on the carpet as it is synthetic, wood floor trated with non toxic sealer and a natural fiber area rug is a safe bet. What about the furniture? Sustainable wood, also non toxic finishes. Cotton or wool matress, cotton bedding, cotton diapers. No wipes.