Measure the cot itself before ordering a replacement. Use a tape measure from one inside edge to the opposite inside edge for both length and width, then check the cot maker’s instructions or assembly document. Do not rely solely on a label such as cot or cot bed, since products with the same general description may have different internal dimensions. Compare your measurements with the stated size of a mattress for a baby cot. Keep a note or photograph of the measurements on your phone before shopping. That simple habit prevents repeated measuring and makes it easier to check a delivery against the original specifications.
Firmness and flatness describe different features. A firm mattress resists pressing down rather than allowing a deep impression to remain. A flat mattress has no raised section, hollow, folded area, or curled portion beneath the sheet. Adult preferences for a soft or deeply cushioned bed do not provide a useful guide for a cot. A mattress can feel comfortable to an adult yet be unsuitable for a baby’s sleeping surface. Age labels alone are not enough either. The mattress still has to match the cot base, retain its shape, and remain suitable for use according to the manufacturer’s instructions.
Inspect a mattress being reused before placing it in the cot. Look over the cover in daylight and check the seams, corners, underside, and edges for tears, staining, dampness, mould, or exposed filling. Press several areas with your hand and compare how quickly they recover. A quick glance cannot confirm that the internal material is still in good condition, especially if the mattress has been stored in a loft, garage, or a room with changing humidity. A clean appearance is not proof that it has retained its original support. Replace it if it is permanently distorted, heavily worn, damp, or no longer fits the cot correctly.
Fit the mattress into the cot before putting on the sheet. Push it gently against each side and inspect the entire perimeter, including the corners that are easiest to miss. It should stay in position rather than sliding away from the cot sides, and no edge should curl upward or sit above the intended base level. Run a hand around the join to check for a visible space. Repeat the inspection after fitting the sheet, because a tight corner seam or unsuitable elastic can pull the mattress out of place. If the cot base has adjustable positions, confirm that the supports are engaged and the base is locked before use.
A waterproof protector can help keep liquid away from the mattress core after a nappy leak or spit up, but it must fit the mattress closely and remain smooth. Loose material, gathered folds, or a protector that is too small can alter the sleeping surface. Do not compensate for a poor fit with towels, folded blankets, extra padding, or improvised layers under the sheet. Those additions can create ridges and change how the mattress feels. Use a fitted sheet made for the mattress, and follow its washing instructions. Repeated hot washing or unsuitable drying may affect the fit or damage the fabric.
Cleaning needs a practical plan. If a sheet becomes wet during the night, remove it and check whether moisture has reached the protector or mattress. Do not place the mattress directly against a radiator or use strong heat unless the care instructions specifically allow it. Some materials can be affected by excessive heat, while trapped moisture may remain in seams or beneath a cover. Allow it to dry in a safe, well ventilated place and inspect it in daylight for odour, staining, or damp patches. For more detailed cot mattress care advice, use the instructions supplied with the particular mattress rather than assuming every material can be cleaned in the same way.
Make the fit check part of each bedding change, especially after replacing a protector or moving the cot. Confirm that the mattress is the intended size, level from end to end, and free from a damaged cover, exposed filling, or compressed edge. Check that the fitted sheet stays secure without pulling the mattress toward a corner. Do not try to correct a mattress that is too small, too soft, or permanently misshapen with extra fabric. Remove it from use and refer to the cot documentation when ordering a replacement. A suitable mattress is one that matches the base, remains firm and flat, and can be cleaned without losing its shape.
