Fit deserves attention before any other feature. Measure the internal length and width of the sleeping space, not the outside of the frame, and write the figures down before ordering. A correctly sized mattress should lie level with no obvious gap at the sides or ends. Run a hand around the perimeter after fitting it, checking that the corners sit down rather than lifting or bowing. A mattress intended for a standard cot may not suit a cotbed once the frame is extended. Check the product dimensions against the document supplied with the cot if you still have it.
Firmness refers to how much the sleeping surface gives under pressure. It is not a measure of whether an adult finds the mattress comfortable. Press the centre and each edge, looking for consistent support and a prompt return to shape. Foam and spring constructions can respond differently, while thickness and the surrounding cover also affect the feel. A permanent hollow, a soft patch or a core that has become misshapen is a reason to replace the mattress. Do not attempt to level an old one with folded blankets, towels or a loose topper beneath the sheet.
Breathability is often mentioned in product descriptions, but the word should not distract from the basic sleep surface. It generally concerns how air and moisture move through or around materials. A cover that feels airy does not make an unsafe sleep position safe, and it does not justify adding a pillow, cushion or positioning aid. Place the baby on their back and keep the cot clear of loose items, following established UK safe sleep guidance. The mattress must remain flat, firm and correctly fitted, whatever materials are used in its construction.
The cover will face milk spills, nappy leaks and regular washing, so inspect its care instructions before buying. A removable washable cover can make routine cleaning easier, while a waterproof layer may help protect the inner core. Neither feature should leave the surface wrinkled, slippery or difficult to fit with a sheet. Follow the stated washing and drying method because excessive heat or unsuitable drying can affect coatings and dimensions. Keep a spare fitted sheet in the nursery. After a night time accident, that small habit avoids leaving bedding in a heap while the cot is needed again.
A mattress passed between siblings needs more than a quick glance in the storage cupboard. Examine it in daylight for mould, lingering odours, broken stitching, stains, damaged edges and any dip in the core. Indoor storage does not guarantee that it is still suitable. If liquid has soaked through the sheet, remove the bedding promptly and check whether the inside is damp. Washing the outer cover cannot reliably clean a wet or damaged inner. Read broader baby bedding guidance if useful, but assess the actual mattress rather than relying on a general care claim.
Before placing the order, read the dimensions, intended cot type, construction, cover details and care label together. Marketing language about comfort or airflow should not replace a physical safety check. Once the mattress arrives, remove its packaging, allow it to settle as directed and inspect every edge. Fit the sheet snugly so it cannot bunch beneath the baby, then check the surface again after laundering. Inspect the mattress periodically, especially after a leak or a move. If it no longer lies flat, has lost its shape or leaves a noticeable gap, replace it rather than modifying the cot setup.
