An average baby has at birth around 3.2 kg (7 pounds, 1 ounce). The heaviest baby ever was born in the US in 1879: 23 pounds, 12 ounces (10.7 kg), but he died 11 hours after being born, as too much or too little above/below the average value decreases fitness. The heaviest baby also to survive was born in 1955 in Italy: 22 pounds, 8 ounces (10.15 kg) at birth.
In September this year a woman from southern Russia gave birth to a 17-pound, 1 ounce (7.7 kg) girl.
But in the case of the twins there is another story: twins deplete severely the mother's organism, so you can imagine that they rarely reach the average weight for a newborn.
Now the British Beth Ryder, 35, of Mount Pleasant, Rawtenstall, Lancashire, has just given born to a pair of twins weighing 19lb (8.55 kg). The boy, Theo, weighs 10lb9oz (4.8 kg) while the girl, Millie, has "just" 8lb 3oz (3.7 kg), being the heaviest mixed sex twins ever born in UK and the pair was born at Burnley General Hospital in Lancashire last week.
The previous holders of the title were Thomas and Grace Houghton-Burnett, weighing 10lb1oz (4.5 kg) and 8lb2oz (3.6 kg), born in 2002.
Ryder has another four children and all had over 9lb (4.05 kg) at birth. Ruder, a student nurse, had herself 11lb13oz (5.4 kg) at birth and her sister Claire 12lb2oz (5.5 kg).
"Large babies run in the family so I knew that they were going to be pretty big. But none of us expected them to be quite so large." she said.
Such a pregnancy was a real burden for Ryder.
"I was absolutely enormous in the weeks running up to the birth and it was so uncomfortable," she said.
Her other children weighed at birth as follows: Emma (17) 9lb9oz (4.1 kg), Leah (8) 10lb11oz (4.8 kg), Lauren (5) 9lb11oz (4.1 kg) and Callum (3) at 12lb1oz (5.4 kg).
But, as scientists explained before, weight at birth is not correlated with weight of the adult individual: Ryder's children are average sized.