How To Choose Disposable Underpads: A Complete Guide To Sizes And Materials

Many people make mistakes when choosing underpads: they choose thick products but still experience leakage; they buy cheap products that cause skin stuffiness; sizes that are too large waste money, while sizes that are too small are insufficient. Whether for postpartum confinement, home care of the elderly, postoperative bed protection, or daily temporary contamination protection, choosing an underpad essentially means choosing “size fit + reliable structure + meeting performance requirements.” By understanding the following points, you can choose a suitable product without relying on sales volume.

I. Choose the Size First: Match the Scenario; Do Not Overbuy Large Sizes or Waste

The core function of an underpad is contamination isolation and protection. Bigger is not always better; matching the use scenario is the most practical and economical. Mainstream specifications and corresponding scenarios are as follows:

1. 40 cm × 60 cm Local Protection Type

Applications: labor and delivery preparation / postpartum lochia, postoperative examination padding, mild intermittent leakage in the elderly, changing pad for children, temporary urine barrier for pets.

Advantages: small single-piece volume, portable storage, low unit cost, no burden for frequent changes; small-area padding is just sufficient and does not waste material.

2. 60 cm × 90 cm Mainstream Home-Care Type

Applications: daily care for bedridden individuals, nighttime use, moderate incontinence with relatively large urine volume, padding during heavy postpartum flow.

Advantages: sufficient protective coverage; not easy to move off the pad when turning over; balances protection area and cost-effectiveness; the preferred specification for long-term home care.

3. 80 cm × 150 cm Full-Bed Protection Type

Applications: severe incontinence, long-term bedridden patients unable to turn over independently, full-bed padding.

Advantages: full coverage of the entire bed, completely preventing bed sheets from becoming soiled. Disadvantages: high unit cost; use in a small area may result in unnecessary waste.

Purchasing tips: For daily small-volume or intermittent use, choose 40 × 60 cm first; for long-term bedridden use and nighttime use, choose 60 × 90 cm first; choose the largest size only for full-bed care.

II. Then Examine the Material: Break Down the Five-Layer Structure Layer by Layer to Distinguish Quality at a Glance

A qualified disposable underpad has a five-layer composite structure. The material of each layer directly determines the user experience and protective performance. From the topsheet to the bottom layer, they are:

1. Skin-Friendly Topsheet: Spunbond Nonwoven

This is the layer in direct contact with the skin. The key considerations are softness, liquid-guiding ability, and safety.

Preferred: spunbond nonwoven + diamond embossing; soft to the touch and not prone to fuzzing. The embossed pattern can guide liquid downward rapidly and reduce liquid retention on the topsheet. Products without migratable fluorescent whitening agents are preferred to reduce the risk of irritation to fragile postpartum skin and sensitive skin.

Pitfalls to avoid: Low-cost products often use inferior thin fabrics that easily pill, stick to the skin after absorbing water, and may even have an odor.

2. Liquid-Guiding Layer: Absorbent Airlaid Paper

A key transitional layer. Its function is to evenly distribute liquid flowing down from the topsheet throughout the absorbent core, preventing liquid from concentrating at a single point, which can cause local saturation and side leakage.

Underpads lacking a liquid-guiding layer often show a condition in which “the center is already soaked while the edges are still dry,” greatly reducing protection efficiency.

3. Absorbent Core: Fluff Pulp + Superabsorbent Polymer (SAP)

This is the core functional layer of the underpad. The key to water-locking ability is not thickness but the content of superabsorbent polymer (SAP).

Fluff pulp: responsible for rapid drainage and diffusion of liquid, allowing liquid to spread throughout the core.

SAP: rapidly swells into a gel upon contact with liquid, firmly locking in water and greatly reducing rewet under pressure.

Common misconception: Many people believe that the thicker the product, the better the absorption. In fact, a thick product may simply contain more cheap fluff pulp with very little SAP; it becomes wet again when pressed, and the surface remains sticky. A thin product with a reasonable SAP ratio can also achieve low rewet and high dryness.

4. Water-Barrier Buffer Layer

Helps share liquid pressure, further reduces the risk of liquid penetration, and improves the overall water-locking stability of the core. It is a standard structure in mid- to high-end products.

5. Waterproof Back Layer: Breathable PE Backsheet

Its function is to block liquid from penetrating to bed sheets and mattresses.

Preferred: A softened microporous PE backsheet can block water while retaining a certain degree of breathability, reducing stuffiness and heat. It does not feel hard, and turning over does not produce a rustling plastic friction sound.

Pitfalls to avoid: Inferior backsheets feel strongly plastic, are hard, brittle, and easily broken, and are completely non-breathable; long-term use can easily cause skin redness from stuffiness.

III. Core Performance Indicators: Do Not Look Only at Thickness; These Data Are More Critical

When choosing, do not be misled by claims such as “ultra-thick” or “ultra-large absorption.” Focus on these quantifiable measured indicators, which have higher reference value:

1. Saturation Absorption Capacity

Meaning: The maximum amount of liquid that a single underpad can hold.

Reference: A conventional 40 × 60 cm product holds approximately 250–300 mL and is suitable for small-volume intermittent liquid; a 60 × 90 cm product holds approximately 500–800 mL and is suitable for medium-to-large liquid volumes.

Recommendation: Choose according to the liquid volume of the use scenario. Bigger is not always better; excessive redundancy only increases cost.

2. Rewet

Meaning: The amount of liquid that returns to the topsheet when pressure is applied after absorption. It is the core indicator determining topsheet dryness; the lower the value, the better.

Reference: The basic national standard requirement is ≤10 g; better-performing products can achieve ≤7 g.

Importance: With underpads that have high rewet, the skin remains in contact with moisture for a long time, which can easily cause redness and discomfort. This is especially important for long-term bedridden individuals.

3. Absorption Speed

Meaning: The time required for a single liquid addition to be completely absorbed by the core.

Reference: Conventional products complete absorption in about 30 seconds. The faster the speed, the less likely liquid is to flow and leak on the topsheet.

4. Topsheet pH

Meaning: The acidity and alkalinity of the underpad topsheet.

Reference: 5.5–6.5 is optimal. Weak acidity is close to human skin pH, mild and low-irritation, and suitable for postpartum and sensitive-skin users.

5. Hygiene Standards

Must comply with GB 15979 Hygienic Standard for Disposable Sanitary Products. The total bacterial count, fungi, and pathogenic bacteria indicators must meet the standards for safer use.

IV. Precise Selection for Different Groups: Match the Right Product and Avoid Mistakes

1. Pregnant and Postpartum Women (Labor Preparation / Confinement): Choose 40 × 60 cm first, with emphasis on a soft topsheet, low rewet, and no fluorescent whitening agents. Suitable for postpartum lochia, delivery rooms, and confinement beds; frequent changes are not a financial burden.

2. Elderly with Mild Incontinence / Daily Home Use: Use 40 × 60 cm during the day for flexible changes; upgrade to 60 × 90 cm at night or when urine volume is relatively large, with emphasis on even absorption and a non-slip backsheet.

3. Postoperative Bedridden / Long-Term Care: Choose 60 × 90 cm and larger sizes first, with large absorption capacity and low rewet, to reduce changing frequency and lower the risk of prolonged skin moisture.

4. Temporary Examination / Multi-Purpose Barrier Pad: Choose a basic cost-effective 40 × 60 cm product. It can be used for gynecological examinations, dressing changes, pet urine barriers, etc.; disposable after use, with low cost.

V. Five Tips to Avoid Pitfalls When Purchasing

Thicker is not better: Thick products are often filled with fluff pulp and have low SAP content; they are prone to rewet under pressure and are stuffier and bulkier.

Do not look only at unit price: Ultra-low-price products often have cut corners in the core, easily broken backsheets, and inferior topsheets; they leak and irritate the skin, resulting in more loss than gain.

Do not use one piece for too long: After liquid saturation, water-locking ability decreases and rewet increases. It is recommended to change promptly once the absorption capacity is reached.

Be wary of absolute claims: Be cautious of expressions such as “zero rewet,” “super absorption,” and “100% leak-free.” These are prohibited absolute terms and are difficult to achieve in practice.

Storage precautions: Store unopened underpads in a cool, dry place and avoid prolonged direct sunlight to prevent aging and cracking of the backsheet.

VI. Usage Tips

This product is a disposable sanitary product and must not be washed or reused.

Place it as flat as possible. During vigorous activity, the corners may be appropriately fixed to reduce displacement.

For sensitive skin or broken skin, a small-area trial is recommended first. Discontinue immediately if itching or redness occurs.

Underpads are daily hygiene and nursing products and are not intended for use as medical devices.