When Gail McInnes gave birth to her son, Kieran, she was in for a big surprise. After 41 weeks of pregnancy, a midwife-assisted labour at the Toronto Birth Centre and two hours of pushing, the first-time mom delivered a beautiful baby boy—all nine pounds, 13 ounces of him.
“When he was first placed on my chest after delivery, I remember just being amazed at the size of him,” recalls McInnes. “I couldn’t wrap my head around how he fit inside my belly.” Though the Toronto mom was 10 days past her due date, she wasn’t expecting her newborn to be quite so…hardy. “We were expecting an eight- or nine-pound baby, but he was even bigger than we expected,” says McInnes.
Victoria Studnicki, a mom in Oakville, Ont., was told that her son, Bryson, would likely be around seven pounds, eight ounces, but upon arrival, her baby was just half an ounce shy of 10 pounds. “He was also very long for a baby,” says Studnicki. “We expect him to grow as tall as his dad, who is six foot two.”
While birth weight estimates during pregnancy are inexact, there are methods used to make an educated guess. “To get an estimate of a baby’s weight before birth, four ultrasound measurements are taken into consideration: head circumference, biparietal diameter, abdominal circumference and femur length,” explains Julia Kfouri, an obstetrician at Mount Sinai Hospital in Toronto.
The average newborn birth weight in Canada is about seven pounds, eight ounces, with a range of five pounds, eight ounces to 10 pounds considered “normal.” While newborn birth weights trended upward for decades in Canada and the United States, these numbers have recently levelled off and even decreased slightly in recent years. This might be attributed to an unexplained increase in low birth weight numbers—a higher number of small babies that bring the national average down—while an increase in gestational diabetes and other maternal factors means that we’re hearing about more big babies, too.
What constitutes a big baby, and what does it mean for mom and baby? Medical professionals generally consider a newborn that weighs between eight pounds, 13 ounces and nine pounds, 14 ounces to be big, and Statistics Canada classifies anything over nine pounds, 14 ounces as a “high birth weight.” You may also hear the term “large for gestational age.”
“There’s a difference between a ‘big baby’ when talking between moms and a big baby, medically speaking,” notes Elyanne Ratcliffe, a paediatrician at McMaster Children’s Hospital in Hamilton, Ont. “Medically, I would only probe further if a baby is more than 10 pounds. From a societal perspective, it could be a different number.”
Essentially, a doctor may not be concerned about an infant tracking to be nine pounds or more, but the idea of giving birth to a baby that size still worries many women. Abigail Corbin, a midwife in Milton, Ont., understands why some moms-to-be might panic. “The trend is, the larger the baby, the harder it is to deliver,” she says, “but that’s actually just one factor in many that affect how the birth goes.”
There are a number of factors that contribute to higher-than-average newborn birth weights, including maternal health, genetics and lifestyle. Gestational diabetes and pregestational type 2 diabetes are also risk factors, and both of these conditions are on the rise in North America. Your height, body type and ethnicity, as well as your partner’s height, body type and ethnicity, can also affect birth weight. Simply put, parents’ genes matter.
Maternal weight, in particular, is a complicated factor, notes Kfouri. “How much weight is gained during pregnancy may translate to a risk of a bigger baby, but this doesn’t only apply to women who are overweight at the beginning of their pregnancy,” she says. “Any woman who gains excess weight during pregnancy may have a big baby.” If a pregnant woman is taking in more calories than necessary or has high blood sugar levels, there will be an effect on the baby, as well as the mother.
Take the case of Michela Preddie, a petite and generally fit woman from Cambridge, Ont., who stands five foot four and weighed 135 pounds pre-pregnancy. She gained close to 70 pounds while expecting her first baby, Jack, who was nine pounds, 14 ounces at birth. “I was instructed by my midwife to meet with a nutritionist to ensure that I didn’t gain more weight and to avoid sugar,” says Preddie. She managed her second pregnancy differently and gained about 40 pounds, but her daughter, Ella, still weighed in at nine pounds, eight ounces.
“Lifestyle is a factor,” says Corbin. “If you have a huge weight gain in pregnancy, it’s not surprising that your baby will be big. But sometimes, it’s completely unexplained and a huge surprise. Some of the biggest babies I’ve seen have come out of women you would least expect to give birth to them.”
Ratcliffe agrees. “The relationships between maternal factors, fetal health and newborn size are probably more complex than what we currently recognize,” she says.
Studnicki recalls that Bryson was a happy, bright baby who slept well and walked early.
McInnes had a similar experience with Kieran, a great sleeper with a sweet temperament. “He was a very happy, easygoing, giggly baby,” she says.
While we might hear, anecdotally, that big babies are less fussy, hit milestones earlier and sleep better because they don’t feed as frequently as smaller infants do, our experts agree that there is no scientific evidence to support these claims. Sure, your big baby might be a jolly little guy. But he’s not guaranteed to be any more easygoing than his smaller baby buddy down the block.
Every baby is different, says Ratcliffe. “It’s also good to be aware of the difference between causation and correlation,” she adds.
I was inclined to believe some of these “big baby” myths myself. My firstborn was a mere five-and-a-half pounds at birth and fed constantly, often waking every 90 minutes during the first few weeks. I’d jump up to feed her, worried that she would wither away otherwise. Though she was a happy baby, she didn’t sleep through the night until close to her first birthday. Her brother was born the following year, weighing seven pounds, 12 ounces—not a “big baby,” by most standards, but huge in comparison to his sister. He slept three- or four-hour stretches from day one and hit every infant milestone early. Was his size a factor? Apparently not, but I can see why the fallacy persists.
While many big babies sleep well, many do not (and plenty of small babies are enviable sleepers). The same logic applies to disposition, infant milestones and newborn feeding habits.
Stephanie Cousens, a mother of three in Burlington, Ont., found this to be true. All of her kids were between eight pounds, 12 ounces and nine pounds, seven ounces. Her third and biggest baby, Anastasia, fed no less and no more than her other two children. “Throughout the day, she wanted to breastfeed every two hours, so that’s exactly what I did,” she says.
Dayna McCarthy, another mom in Burlington, Ont., had a similar experience with her three children, born between seven pounds, 10 ounces and eight pounds, 15 ounces. “They were all hungry, and I can’t say I noticed a difference,” says McCarthy.
Ratcliffe notes that newborn babies have a physical need to eat frequently, regardless of how much they weighed at birth or whether they seem scrawny or chunky. “It’s not until they’re older that, physiologically, they can maintain their blood glucose,” she says. “In early life, they also need to feed often to stay hydrated.”
We might also look to the fact that women commonly have larger babies every time they give birth. Knowing this, it’s reasonable to surmise that bigger babies are often (though not always) born to more experienced moms. If experience leads to confidence and less new-mom stress, it could be a valid factor.
“I was way more laid-back the third time around,” says McCarthy. “I didn’t pay any attention to milestone charts, worry about when she crawled or walked or stress about how much she ate. I also perceived her as less needy than my first two babies. I already knew that all babies are very different. They are resilient and eventually achieve their milestones—there's no need to compare them.”
In the end, your baby’s personality and development will have little to do with the number of pudgy rolls on their adorable legs, and their birth weight will be reflective of factors both within and beyond your control. There may be no official link between your baby’s size and behaviour, but there’s one thing that most parents can agree on: A squishy, squeezable baby is super-cute.