What do Twins Normally Weigh at Birth?

When you find out you’re having twins, there’s lots of questions and one of those for us (especially as the pregnancy went on) was how much do twins normally weight at birth? Y

ou’re so used to hearing how much a singleton pregnancy baby weighs at birth but what do twins weigh? Do they weigh the same as singleton babies? We explore the topic and share our findings on what twins normally weigh at birth even including what triplets weigh too!

If you find this topic interesting, you might also find our article on the average week that twins are born.

Why are Twins Born Smaller than Singletons?

Before we explore the topic of the weight of twins at birth, it’s important to talk about why twins can be a bit lighter than a singleton pregnancy and the key factor that contributes to this.

A large part of twins being born at a lower birth weight compared to singletons is due to not running to full-term like most singleton pregnancies do. For this reason, most twins are born preterm and aren’t fully developed which results in the lower birth rate compared to singletons. They unfortunately aren’t given that extra time in the oven (Sorry, I have a love/hate relationship with that saying!) giving them the chance to properly develop and put on similar weight levels you would see with a singleton pregnancy.

Weight Difference in Twins During Pregnancy

According to the sources we reviewed, the average birthweight of twins is quite interesting. In the year of 2017, they noted the following:

  • 19% of twins were born preterm (prior to 34 weeks)
  • 59% of twins were born prior to 37 weeks

The above is quite interesting especially when you compare this to singleton pregnancies. Generally only 9% of singleton pregnancies are born before 37 weeks with 2% born before 34 weeks. A big difference to the 19% seen in twin pregnancies!

While from a birth weight perspective, this is grouped into three different groups with ‘low birth weight’ being less than 2,500 grams or 5 pounds and ‘very low birth weight’ being less than 1,500 grams or 3 pounds 5 ounces. What do the numbers tell us?

  • 55% of twins are born with low birth weight (less than 2,500 grams)
  • 9% of twins are born with very low birth weight (less than 1,500 grams)

As we mentioned earlier in the post, there’s a correlation between being born early (prior to 37 weeks) and a low birth weight. For babies that are born between the 37 week mark, they’re often born with a lower birth rate as they haven’t been given the chance to properly develop and be born with a higher weight like you would see with a singleton pregnancy.

Average Birth Weight of Triplets

Again, according to the same source we shared earlier, triplet pregnancies get even more interesting where generally triplets are born less than half the size of a singleton baby. While in terms of weight, 30% were born with very low birth weight (less than 1,500 grams). Almost 20% more than a twin pregnancy. Interesting!

In terms of when triplets are born when compared to twin pregnancies, this is also quite interesting where:

  • 67% of triplets are born early preterm (born 34 weeks)
  • 98% of triplets are born preterm (before 37 weeks)

Similarly again to twin pregnancies, there’s a trend here again where due to being born early, this also results in triplets being born with a low birth rate compared to singleton pregnancies.  In the case of triplets, it’s almost near certain that they will be born before the 37 week and therefore resulting in being born with a lower birth rate compared to singleton pregnancy.

Summary / Closing

So there you have it – on average, 59% of twins are born prior to 37 weeks and with that, results in 55% of twins being born with low birth rate (less than 2,500 grams) while 9% of twins are born with a very low birth rate (1,500 grams). This low birth weight is largely caused by the fact that twins are born early which means they aren’t able to fully develop like a singleton baby would who would most likely run to a ‘normal’ term of 37+ weeks.

We hope this article on the average birth weight of twins has been useful for you!

Thanks for reading and we hope you found this article useful!

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