Why Your Baby’s Diaper Leaking: 8 Causes and How to Fix Each One
By Teddyy Editorial Team | Last Updated: May 9, 2026
You’ve just changed your baby’s diaper, and within minutes, you notice a leak. That’s often the moment disappointment kicks in. You chose what was supposed to be the best newborn diaper for your baby, yet now you’re changing everything all over again, from the outfit to the bedsheet. It can really test your patience, especially during an already exhausting day.
Newborn diaper leaking are a frustrating part of parenting that almost every mother experiences at some point. The good news is that leaks usually happen for a reason, and once you identify the cause, they can often be prevented.
In this guide, we’ll explore some of the most common reasons behind newborn diaper leaks and simple ways to fix them.
Wrong Diaper Size: The Most Common Mistake
The first thing to check is whether you’ve chosen the right diaper size for your baby. This is one of the most common mistakes parents make. A diaper that is too small can cause rashes, irritation, and discomfort, while a diaper that is too loose or too big may lead to frequent leaks.
While diaper size charts are helpful, babies don’t all grow in the same proportions. Their body shape matters just as much as their weight when choosing the right fit.
How to Tell if the Diaper Size is Wrong
- Red marks around the thighs or waist may mean the diaper is too tight
- Gaps around the legs can indicate the diaper is too loose
- Frequent leaks are often a sign of an incorrect fit or size mismatch
How to fix it?
- Always check your baby’s current weight and compare it with the diaper size chart.
- If your baby is between sizes, try both to see which fits snugly.
- Sizing can change quickly for younger babies, especially in newborn size diapers, so reassess frequently.
Incorrect Diaper Fit: Small Mistakes Can Lead to Leaks
Even if you’ve chosen the right diaper size, leaks can still happen if the diaper is not fitted properly. Small fitting mistakes often create gaps that allow urine to escape.
Common Diaper Fitting Issues
- Tabs fastened unevenly
- Waistband sitting too low or too high
- Leg cuffs tucked in instead of flared outward
How to Fix It
- After putting on the diaper, gently run your fingers around the leg openings to pull out the ruffles properly
- Make sure the waistband sits comfortably just below the baby’s belly button
- Fasten both tabs evenly to ensure a balanced and secure fit
Whether you are using taped diapers or diaper pants, the principle remains the same: the diaper should fit snugly and securely without being too tight.
Blowouts vs Side Leaks: Not All Leaks Are the Same
A leak can happen due to different reasons, so do not treat them the same way.
Blowouts (back leaks)
These happen in the following situations:
- The diaper is too small
- Your baby has a full bowel movement
- The waistband isn’t high enough
Side leaks
These happen in the following conditions:
- The leg cuffs are not adjusted properly
- The diaper is too loose
- There’s too much movement
How to fix it?
- Size up and check if the waistband fit is higher for blowouts.
- Adjust leg cuffs and go with a snug fit around thighs in case of side leaks.
Your Baby’s Sleep Position Matters More Than You Think
Night-time leaks can feel especially frustrating. Your baby sleeps peacefully through the night, only to wake up with soaked clothes and bedding.
Why Do Night Leaks Happen?
- Babies who sleep on their back may experience leaks from the back of the diaper
- Side sleepers may notice leaks around the legs
- Longer sleep hours mean the diaper needs to absorb more for extended periods
How to Prevent Night-Time Leaks
- Choose highly absorbent diapers designed for overnight use
- Make sure the diaper sits slightly higher at the back for better coverage
- Consider switching to diaper pants, which offer a more secure fit during movement and sleep
A good overnight diaper, such as Teddyy diapers, is designed to provide longer-lasting absorbency and comfort through the night.
Absorbency Limit Reached
Sometimes, leaks happen simply because the diaper has reached its absorbency limit. This is especially common when:
- Your baby is feeding more frequently
- Diaper changes are delayed for too long
- Night-time usage exceeds the diaper’s absorption capacity
How to Fix It
- Change diapers more frequently during the day
- Use high-absorbency diapers at night
- Avoid waiting until the diaper feels overly heavy or saggy
Even the best newborn diapers have a limit, so timely changes are important to keep your baby dry and comfortable.
Brand Fit Differences: Not All Diapers Fit the Same
Two diapers may carry the same size label, but their fit can still vary from brand to brand. Every diaper brand follows a different design and fit structure.
Why Switching Brands Can Help
- Some diapers fit babies with chunkier thighs better
- Some are more suitable for leaner body types
- Some offer better elasticity, stretch, and overall comfort
What You Can Do
If leaks continue even after trying the right size and fit adjustments, it may be time to try a different brand. You may find that one brand’s diaper pants fit your baby perfectly, while another brand in the same size may not provide the same comfort or leak protection.
Skin Creams and Oils Interfering with Absorption
Diaper rash creams or oils can affect the way a diaper absorbs moisture.
Why does it happen?
- Creams create a barrier
- Liquid does not get absorbed quickly
- Leads to overflow and leaks
How to fix it?
- Use only a thin layer of cream.
- Allow it to absorb before putting on the diaper.
- Choose diapers with strong absorption layers.
Newborn-size diapers already have a limited capacity, so this is important.
Bringing It All Together
Diaper leaks can feel like a never-ending cycle, but you can fix it once you understand the cause.
It is about doing a few small things differently most of the time. Checking the fit, adjusting the size and noticing patterns can make your day and night easier.
Sometimes, what works for one baby may not work for another, which is okay. Take some time to figure out what works best for your baby. Leaks will become rare with these simple changes, and you do not have to deal with them repeatedly.
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Frequently Asked Questions
Why does my baby's diaper keep leaking at night?
The reason for night leaks is that the diaper cannot absorb any more or does not fit properly for your baby’s sleep position. Try to use a more absorbent diaper with a snug waistband.
How do I know if a diaper is too small or too big?
A diaper that’s too small leaves red marks and causes blowouts. But a loose diaper leads to gaps and side leaks. Checking your baby’s weight against a diaper size chart helps you choose the right fit.
Why does the diaper leak from the back (blowout) so often?
It happens when the diaper is too small or not pulled up high enough. You can size up on the diaper or adjust the waistband to reduce such problems.
Does diaper brand make a difference in leakage?
Different brands have different fits and absorption levels. Switching brands can sometimes solve leakage problems.
How should I fit a diaper correctly to avoid leaks?
The diaper should sit snugly below the belly button, with evenly fastened tabs and leg cuffs pulled out. There should be no gaps or tight marks.