A Letter to Past Me: Stop Panicking About Normal Baby Weight

Dear Tom from two years ago, currently sweating through a grey marl t-shirt in Room 4 of the local NHS clinic.

You're sitting in a plastic chair that's somehow both sticky and cold, balancing two identical infant car seats on your knees. Twin A is screaming with the raw, sustained fury of a displaced emperor, while Twin B is asleep, completely dead to the world, drooling slightly onto a pristine white muslin. You're staring at the digital scales in the corner of the room like they're an unexploded bomb. You're terrified.

You sit there staring at the other parents, wondering what a normal baby weight at birth actually looks like, because the tiny human in the pram next to you appears to be the size of a six-month-old golden retriever, while your two look like slightly damp, angry pigeons. You're convinced you're doing it all wrong. You're mentally tallying every milliliter of formula and every agonizing minute spent hooked up to the breast pump, certain that the health visitor is about to revoke your parental license.

I'm writing to you from the future (they're two now, they survive, they currently eat old chips off the pavement when I'm not looking) to tell you to please, for the love of everything holy, stop obsessing over the grams.

The great fluid dump of week one

Right now, your brain is entirely consumed by the drop. Nobody warned us about the drop, did they? They hand you these fragile little creatures, you take them home, and within four days, the midwife comes round, pops them in a terrifying hanging sling that looks like a medieval torture device, and tells you they’ve lost nine percent of their body mass.

You nearly passed out. I remember you gripping the kitchen counter, frantically doing percentage calculations in your head, convinced they were starving to death under your watch. What the doctors cheerfully fail to emphasize to sleep-deprived, weeping new parents is that newborns arrive absolutely pumped full of water (like a biological water balloon, really) and they spend the first week aggressively peeing it all out.

Our paediatrician, Dr. Harris—a man who perpetually looked like he needed a strong cup of tea and a fortnight in Mallorca—later explained that this initial plummet is just basic biology, not a reflection of my catastrophic failure as a father. It's entirely expected for them to drop up to ten percent of their initial mass, and as long as they claw their way back up to that starting line by week two, everything is fine. You don't need to order digital baking scales from Amazon to weigh them before and after every feed. I repeat: cancel the Prime delivery.

The absolute tyranny of the little red book

We need to talk about the percentiles in the red health record book, because they're currently destroying your life. You have turned into a deranged amateur statistician.

The health visitor plotted Twin A on the 50th percentile, meaning she's squarely in the middle of the pack, a perfectly average British baby. But Twin B—sweet, tiny, bird-like Twin B—was plotted on the 9th percentile. You looked at that graph and immediately spiraled into a panic, assuming she was fading away into nothingness. You spent three consecutive nights awake at 3am, staring at the ceiling, wondering how you could force-feed more calories into a creature whose stomach is the size of a walnut.

Here's what I wish I understood then: the actual number on the percentile chart doesn't matter in isolation. If a baby is on the 9th percentile, it just means that in a room of 100 babies, 91 of them would beat her in a pub fight. That's all. Dr. Harris told me that the only thing doctors actually care about is the curve. If she starts on the 9th percentile and happily trundles along the 9th percentile line for the next year, she's thriving. She is just a small person. (Spoiler alert: my wife is 5-foot-nothing; we were never going to breed linebackers).

The only time anyone gets remotely concerned is if a baby is merrily cruising along the 50th percentile and suddenly plummets down to the 10th over a short period. That’s a red flag. But simply existing as a small baby? That’s just genetics.

That terrifying four month bulk up

There's going to be a period soon where it feels like all they do is eat, sleep, and ruin their outfits. It’s relentless. But it makes sense when you look at the sheer physics of what their bodies are trying to accomplish.

During one of our exhausted check-ups, Dr. Harris casually mentioned that most babies double their birth weight by 4 months. I remember blinking at him slowly, trying to process the maths. If I doubled my weight in four months, I'd be a medical marvel and probably dead. For them, it's just a Tuesday.

This rapid expansion phase is exhausting, and it tragically overlaps with the exact moment their teeth decide to start making a painfully slow exit through their gums. They will be ravenous for milk, but their mouths will hurt too much to drink it comfortably, resulting in a lot of angry crying from everyone involved.

This is precisely when you need to lean into distractions. I vividly remember the afternoon I finally caved and bought the Plush Monster Rattle Teething Toy in slate grey. Honestly, it saved what little was left of my sanity on a rainy afternoon when Twin A decided her own fist wasn't crunchy enough to soothe her gums. It’s just an organic cotton crocheted head on a wooden ring, but because it’s untreated wood, it has that perfect, hard resistance they crave. She gnawed on that poor monster’s face for three straight months. It survived being dropped in puddles, thrown at the cat, and washed in the sink, and it never fell apart.

We also tried the Panda Teether around the same time. It’s perfectly fine—food-grade silicone, totally safe, easy to chuck in the dishwasher when it inevitably gets covered in mysterious floor lint. But for whatever reason, Twin B was deeply suspicious of the panda's face. She would hold it at arm's length, give it a withering look, and throw it out of the pram. It ended up being a very expensive bath toy. Babies are fickle critics.

If you're looking for things that will actually survive the twin apocalypse and not leach terrifying chemicals into their rapidly growing bodies, it's worth having a browse through the Kianao organic baby collection. Just save yourself the headache and buy two of whatever you get, because sharing is a concept they'll fundamentally reject until they're at least thirty.

What a full nappy honestly tells you

I know you want a definitive formula to prove they're gaining weight properly. You want a spreadsheet. You want a daily readout. But you need to put down the digital baking scales, look at the actual living creature in front of you, and have a strong cup of tea.

You don't need to weigh them daily. It will only make you crazy. Instead, you just need to become uncomfortably obsessed with their bodily fluids. The best, most reliable indicator that your baby is taking in enough calories and growing as they should is how many wet nappies you're hauling out to the bin every day.

After the first week, if they're producing five or six heavy, wet nappies in a 24-hour period, they're hydrated. If they're pooping regularly (and believe me, you'll know), things are moving through the system. I spent so much time agonizing over whether they took 3 ounces or 4 ounces at a feed, when I should have just been looking at the output. If it’s coming out in respectable volumes, it means it went in.

Look at their general demeanor. When they finish a feed, do they look like a drunk man who has just polished off a massive kebab—relaxed, floppy, and satisfied? Are they starting to grab at things, look at your face, and hit those basic physical milestones? Then they're fine. They're perfectly, boringly fine.

When to honestly bother the doctor

I'll allow you to worry in very specific circumstances, because I know you won't stop entirely.

If they become terrifyingly lethargic—not just sleepy, but difficult to wake up for feeds. If their nappies are bone dry for hours on end. If they're dropping off their established curve entirely, or if every single feed is a screaming, arching battle of wills that ends in projectile vomiting across the living room rug. That’s when you call the GP. That’s when you bypass the frantic late-night internet searches and honestly ask a medical professional about reflux or allergies or milk protein intolerances.

But right now? In this sticky clinic room? They're okay. Twin A is screaming because she’s hot, and Twin B is asleep because she’s tired. They're going to grow at their own weird, chaotic pace. Throw the little red book in a drawer, trust your gut, and maybe buy a backup teether to keep in your pocket.

I highly think keeping the Squirrel Teether permanently attached to the pram bag. When the four-month growth spurt hits and they turn into ravenous, teething goblins, you’ll thank me.

Yours in permanent exhaustion,

Tom

The Real Questions Every Stressed Parent Asks

Why does my baby look so skinny compared to my friend’s baby?
Because genetics are wild, and babies aren't standardized factory parts. My twins share the exact same DNA and one looks like a bouncer at a nightclub while the other looks like a delicate Victorian poet. As long as your GP is happy with their personal growth curve, ignore the Michelin-tyre baby at your local playgroup. It's not a competition.

Should I wake them up to feed them so they gain more?
Unless your doctor specifically looked you in the eye and told you to do this because of medical concerns (which they sometimes do in the very early weeks), absolutely don't wake a sleeping baby. Sleep is when they literally secrete growth hormones. I used to poke Twin B awake to force milk into her, and all I got was an angry, exhausted infant who refused to eat anyway.

Is the 50th percentile the "goal" for normal weight?
No, and this misunderstanding cost me a year of my life. The 50th percentile isn't an A+ grade on a test. It's just the median average. The 10th percentile is completely normal. The 90th percentile is completely normal. The only goal is your baby staying roughly on whatever line they started on.

How accurate are the clinic scales anyway?
Honestly? One time the health visitor weighed Twin A, frowned, stripped off her onesie, weighed her again, and she had somehow gained 200 grams naked. The baby was wiggling, the scale was old, and someone bumped the table. Take the clinic numbers as a rough estimate, not the gospel truth, and definitely don't try replicating it at home with your kitchen scales while they’re screaming.

Does formula make them gain weight faster than breastmilk?
Dr. Harris told me that breastfed babies tend to chunk up really fast in the first two or three months, and then their weight gain slows down. Formula-fed babies sometimes have a steadier, more consistent climb. We ended up doing a messy mix of both because of the twin logistics, and frankly, they both ended up on exactly the same growth curve by their first birthday. Just feed them however keeps everyone sane.