On Thursday, the largest ever baby born naturally in Spain was delivered of a British mother, Maxine Marin who – in a footnote that I will never stop finding annoying – was said not even to need an epidural. Baby Maria, at a massive 6.1kg (13lb 7oz), is said to be in perfect health. She is a beautiful thing, with one of those wise-baby faces and a full head of hair; she looks about six months old.

This comes exactly a week after the appearance of the heaviest baby – Jasleen – ever to be born in Germany. Her mother had untreated gestational diabetes, which leads to large babies, so the baby's condition isn't so good, though nor is it life-threatening.

While two swallows don't make a summer, and two giant babies do not confirm a giant baby trend, obstetricians nevertheless detect an upward curve. Daghni Rajasingam, consultant obstetrician and Royal College of Obstetricians and Gynaecologists spokeswoman, says: "We are having, on average, larger babies being born. There are several reasons for it, the biggest of which is the global epidemic of obesity and diabetes. If you're obese you have a higher risk of having a large baby anyway, even if you don't have diabetes.

"This idea of having a bonnie baby, and that being a good thing, is an old wives' tale. Babies who are born bigger have a higher risk themselves of being obese, developing diabetes and heart problems. You want an appropriate-sized baby, is the thing."

What's appropriate? What's normal? What's macrosomic (or, if you prefer, "large")? The numbers have come down a bit – you're now screened for gestational diabetes if you've had a previous birth of 4kg, or 8lb 13oz (it used to be 4.5kg). But the key issue for people with near-hand experience of a large baby is probably not the threshold of what constitutes "large", but rather, "how do I get it out?"

Sheena Byrom is chair of the Royal College of Midwives (RCM) campaign for natural birth. "I do see more and more big babies, yes. But it doesn't have to mean a more difficult labour. There is only one thing that's harder with big babies, and I mean really big, when the shoulders get stuck. But it's very rare, and it doesn't have to happen, if women stay mobile during labour." Byrom tries not to use the word "big" with pregnant women, preferring "healthy". "If you're told by your midwife or doctor that you're going to have a big baby, fear sets in, and then childbirth will not be as smooth." But then, if you're not told, there's a chance you will have a surprise giant baby.

A woman six weeks from her due date with her second child had a first baby of 4.7kg (10lb 6oz).

"The scan isn't a very good predictor. I was 10lb 1oz when I was born, so I knew he was going to be big, but they kept saying: 'Yeah, yeah, we'll see how it goes.' My mum said have a c-section. She even did a little note to go to my consultant."

She got a note from her mum! But had her son naturally anyway … "He didn't get stuck, he just took a long time to come out. I actually burst all the blood vessels across my shoulders."

She said she wanted to remain anonymous, and I said I understood. But actually, I don't understand, and if I were her, I'd want someone to make a statue of me.

Of course, huge babies aren't entirely a 21st-century phenomenon. Val Mellors had three boys, the first 10lb (the other two smaller) 33 years ago. "When I'd had him, there was a hospital inspector visitor woman doing the rounds, and she asked me why I was in. I said: 'It's a maternity unit. I've just had a baby.' And she said: 'But why are you back?'" And that persisted, throughout her son's childhood – he was young but tall for his year, and teachers would always judge his age by his height rather than his actual age. "But I loved having a large baby. I always felt that he was really robust."

Mervi Jokinen, a midwifery adviser at the RCM, says: "It's inevitable in one's mind that one might fear a big baby. In my time as a midwife, sometimes when you said: 'You should really stop smoking during pregnancy, one of the reasons is low birth weight,' they would say: 'Well that's what I want anyway.'"

Just as many of us can never walk past a baby without having a look, people can never have a look at a giant baby without making an especially congratulatory remark.

Mellors remembers: "People would always say how healthy and bouncy he looked. Then they would say: 'It's lucky he's not a girl.'"