Duo for Delivery: How Fast Do Twins Grow?

July 18, 2017



So you’re having twins? No doubt you have been scouring the internet and bookstore trying to get your hands on all the pregnancy things to figure out what is going on inside your body. It really is incredible to learn about how your body changes and how your babies are growing! Then you talk to a few older ladies in your neighborhood who start telling you some interesting old wives tales. Things like how you carry being indicative of sex, indigestion clueing you in that your baby is hairy, and conception position impacting your gender chances.  Oddly enough, the old hairy baby/heartburn thing appears to have a correlation according to researchers at John Hopkins University. There are so many bits of information to consider!

Sifting through the ‘alternative facts’ and the truth isn’t always easy. One of the interesting questions you may come across is how fast are your two growing before they are due? Do they grow at the same rate as their singleton amigos or are they on a slower or faster track? Is 40 weeks still the gestational time frame for twins? Let’s dig in and find out.

Though these might seem like straightforward questions, the answers are not quite so simple. Most experts seem to agree that growth for twins slows down at about 30 weeks as the twins compete for nutrients and space. Research has shown that up until about 28 to 30 weeks, twins grow at the same rate as their singleton counterparts. In the early stages, growth is the same according to University of Nottingham. Dr. Barbara Luke, author of the book “When You’re Expecting Twins, Triplets, or Quads: Proven Guidelines for a Healthy Multiple Pregnancy,” confirms that “[r]esearch has shown that the overall pattern of growth before birth for well-grown multiples does not differ from that of singletons until late in pregnancy, when the rates of growth for multiples slow down."

Depending on the type of twin pregnancy you are having, your twins may differ in size during a normal twin pregnancy. Generally, practitioners don’t become too concerned until they see a difference of more than twenty percent and particularly for twins that are sharing a placenta. The more important thing is to see a consistent growth curve for that particular twin.

So if they are slowing down in growth towards the end of your pregnancy, when exactly do they reach full gestation? A ‘full term’ singleton baby is born between 39 and 41 weeks. Anything before 37 weeks is considered pre-term. Some research has indicated that 37 weeks would be the optimal gestation for twins. Other research suggests that 38 weeks would be optimal time for delivery.

A key thing to consider is that typically lung and brain maturation occurs in the 37 to 40 week period. There was a widespread belief that lungs matured more rapidly in twins due to stress hormones and this does not seem to be the case. And although 35 weeks is the average time for the delivery of twins (factors such as space and amniotic fluid come into play), if possible waiting a few more weeks would be optimal for a normal twin pregnancy to avoid respiratory issues. This may not be possible for many twin pregnancies, so relax and cook those little biscuits as long as your body is able to. We are so fortunate to have teams of amazing neonatal practitioners ready to intervene at a moment’s notice. With each passing day, science learns new things and advances best practices. It’s incredible what we now know about the chubby little cherubs you are cooking up. Enjoy this amazing adventure!.