If you've had an ultrasound scan with First Encounters before, you may remember seeing the model that we keep in the clinic to show our visitors:

That is a model of a foetus at 20 weeks gestation. We often show it to the expectant parents who come to us for a scan, and almost without exception, they're always surprised to see how small the baby still is at that point. By 20 weeks, the mother's 'baby bump' is usually becoming fairly pronounced, and if you've ever been present during a 3D/4D scan, you'd be forgiven for thinking that babies are rather large indeed by that stage!
 
4D Scan Image
 
Watching your unborn baby on a big TV screen tends to make them seem larger than they actually are!
 
Many an expectant mother has asked us how big her baby is at X weeks, and so we thought we'd put together a handy guide to baby size  and how it changes from conception to birth. We hope that this will give you a clearer idea of your little darling's current size!

How big is my baby at...

  •  ...4 weeks? Less than a twentieth of an inch long and less than a twentieth of an ounce in weight. At this point, your unborn child is just a tiny embryo, no bigger than a poppy seed. 

  •  ...8 weeks? About 16mm (0.63 inches) long, or roughly the size of a single baked bean. That's more than fifteen times larger than the 4-week-old embryo, although the baby's weight has barely changed since then - we're still talking about a small fraction of an ounce at this stage. 

  •  ...12 weeks? 2-3 inches long and about half an ounce in weight. You're currently carrying a foetus that's more or less the same size as a lime.

  •  ...16 weeks? Just under 5 inches long and about 3.5 ounces in weight. You're now in your second trimester, and the baby is about as big as an avocado.

  • ...20 weeks? 6 and a half inches in length, 10 and half ounces in weight. At this stage, your foetus is a mite shorter than a carrot but weighs quite a bit more.

  • ...24 weeks? Roughly 12 inches in length and somewhat over 1 pound weight-wise. Your unborn baby is growing quite rapidly now, and their current size is roughly similar to that of a 500ml bottle of water.

  • ...28 weeks? By now, your baby should measure about 15 inches and weigh a little more than 2lbs. Picture an aubergine and you won't be too far off.

  • ...32 weeks? Nearly 17 inches, with a weight of around 3lbs 12oz. Remember how, at 24 weeks, your baby was about the size of a 500ml bottle of drink? Well, now he or she is closer to a 1.75 bottle.

  • ...36 weeks? 18.66 inches - that's just over 47cm - in length, and the best part of 6lbs in weight. By now, your baby is roughly the size of a melon.

  • ...40 weeks? Now that you're almost ready to give birth, your baby likely weighs 7-9lbs (although this varies quite a lot) and measures between 20 and 21 inches.
If you'd like to take a closer look at your unborn baby, click here to browse the 3D/4D scan packages available at your nearest First Encounters Ultrasound clinic.