Winter babies vs summer babies

Does it really make a difference when my baby is born?

Believe it or not, whether your child is born in winter or summer may affect her at certain times of her life. It's called the season-of-birth effect, although it has nothing to do with astrology!

No one understands fully why this is the case. But what you'll eat during pregnancy will probably change from season to season. This in turn may affect the amount and type of nutrients your baby receives in the uterus (womb) (Watson and Macdonald 2007).

Levels of vitamin D may also play a part. Your vitamin D levels vary depending on the time of year, what you eat and your exposure to UV rays in sunlight. Vitamin D is thought to play a vital role in regulating our immune systems and in developing our bones.

Seasonal temperature changes and exposure to winter viruses may also explain differences between babies born in the spring, summer, autumn and winter.

Is it healthier to be born at a certain time of year?

It's really hard to say, as so many factors will influence how healthy your baby is as she grows. But research does show that children born between June and October are likely to be slightly taller and have bigger bones than winter-born children (Sayers and Tobias 2008). The reason is thought to be related to vitamin D exposure during pregnancy.

Researchers measured levels of vitamin D in women when they were 37 weeks pregnant. Those with the most exposure to the sun had the highest levels of vitamin D in their blood. Their children had bigger bones and were 0.5cm taller on average than children born in the darkest months.

Babies born in autumn and winter are more likely to develop food allergies (Mullins et al 2011, Vassallo et al 2010). No one knows exactly why, but sunlight exposure during pregnancy and vitamin D levels may play a role.

Asthma is also more common in autumn-born children. During winter, we stay indoors with the windows shut and the heating on. So one possible reason is increased exposure to allergens, such as house dust mites, during the first few months of life (Knudsen et al 2007).

When it comes to vision, babies born in summer are more likely to be short-sighted than children born in winter. This may be because of increased exposure to natural light during pregnancy and the first few months of life. Even when your baby's in your uterus, she'll be able to see light as a rosy glow through your belly. From as early as 26 weeks your unborn baby's eyes will open and she'll begin to see.

Children born in spring and summer are also more likely to suffer from seasonal depression or Seasonal Affective Disorder (SAD), than those born in winter (Natale et al 2007, Tonetti et al 2012). Again, this may be to do with how exposure to more natural light in early life programmes the nervous system.

How will the season my baby's born in affect me?

Given the weather in the UK, it may be slightly easier to deal with certain milestones if your baby is born in the summer.

Those early weeks with your new baby may seem easier to cope with. Strolls in the park, or being able to sit in the garden, can relieve you of that feeling of being cooped up inside with a small baby. It may be easier to socialise and meet other new mums when it's light and warm outside.

Of course, babies do have a habit of not arriving to schedule, but any mum will tell you that it's easier to organise birthday parties in the warmer months. When you've a horde of small children to entertain, being able to throw a party at the local park or at the beach is a great option.

Another possible advantage to having a summer baby is potty training. Your toddler may be ready to give potty training a go from the age of two. Letting your toddler run around without layers when it's warm can take some of the strain out of dealing with accidents. Having said that, most toddlers run to their own timetable when it comes to potty training, so season of birth may make little or no difference.

Although some mums find having a summer baby easier, others love having their baby in the winter, as they feel as though they have received an extra Christmas present!

Summer or winter, there's no evidence to show that your baby's season of birth affects what type of mum you'll be.

Which babies sleep better: summer or winter babies?

We don't know whether summer or winter babies sleep better as babies. However, by the time your child becomes a teenager, if she's a spring and summer-born child, a couple of studies have found that she's more likely to stay up late (Natale et al 2009, Tonetti et al 2011).

Spring-born children also tend to enter deep sleep later in the night than autumn-born children, who tucked themselves up much earlier.

One possible reason for these findings is that our internal body clocks (circadian rhythms) may be affected by our exposure to sunlight at birth.

Babies born in the spring are exposed to increasing amounts of sunlight in their early months, while summer-born babies are exposed to the greatest amounts. As a result, they may take longer to feel tired, making spring and summer babies more likely to stay up late.

Can my baby's birth date affect how well she does at school?

It's true that children born in the autumn and winter in the UK tend to perform better in primary school tests. However, this is not because they're cleverer. It's simply because children born in the summer are the youngest in their year group when the school term starts in September.

The advantage in the classroom of autumn-born children is noticeable early on, but it becomes less obvious as they grow.

Outside of school, one study did find that winter-born children tend to score higher in reasoning and physical development tests as babies and seven-year-olds, than children born in summer (McGrath et al 2006).


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Mullins RJ, Clark S, Katelaris C, et al. 2011. Season of birth and childhood food allergy in Australia. Pediatric Allergy Immunology 22:583–589

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Natale V, Adan A, Fabbri M. 2009. Season of birth, gender, and social-cultural effects on sleep timing preferences in humans. Sleep 32(3):423-6

Sayers A, Tobias JH. 2008. Estimated maternal ultraviolet B exposure levels in pregnancy influence skeletal development of the child. J Clin Endocrinol Metab 94(3):765–771. Online first: 30 Dec

Tonetti L, Fabbri M, Martoni M, et al. 2011. Season of Birth and Sleep-Timing Preferences in Adolescents. Chronobiology International 28(6):536-540

Tonetti L, Fabbri M, Martoni M, et al. 2012. Season of birth and mood seasonality in late childhood and adolescence. Psychiatry Res 30;195(1-2):66-8. Online first: 15 Aug

Vassallo MF, Banerji A, Rudders SA, et al. 2010. Season of birth and food allergy in children. Ann Allergy Asthma Immunol 104(4):307-13

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