13 weeks pregnant: Your baby is the size of a peach

Wave goodbye to the first trimester at 13 weeks pregnant! Uncover what this pivotal week holds for you and your rapidly growing baby.

Welcome to your second trimester and hello baby bump! What else is happening in week 13 of your pregnancy?

Your body at 13 weeks pregnant

Your placenta is now well established and oxygen and nutrients from your bloodstream are flowing across it to your baby. The placenta is an amazing organ – created especially for pregnancy – which acts as a substitute lung, liver and kidney for your baby. You’ll start to have a small bump!

Your baby at 13 weeks pregnant

During the first trimester, most of your baby’s energy was devoted to development; from now on, she (or he!) will concentrate more on growing. In the next 10 weeks or so, your baby’s weight will increase from around 28g to nearly 400g and her length – now about 7.5cm from crown to rump will more than double.

What’s happening now

Your baby’s neck is getting longer and her chin’s becoming more pronounced, making her look more human. She’s now about the size of a peach, and soft, downy hair (lanugo) is growing on her upper lip and eyebrows. Your baby’s external genitalia have now developed enough for an experienced ultrasonographer (ultrasound operator) to tell whether you’re having a girl or a boy.

Sleeping like a baby

It’s difficult to measure babies from head to feet at this stage of development because they tend to be curled up in the foetal position for most of the time. For this reason, they are generally only measured from the crown (top of the head) to the rump (bottom) until about the sixth month of pregnancy, when their legs uncurl and stretch out.

Did you know?

If you’re having identical twins, they can cuddle and ‘kiss’ each other from 13 weeks.

Great umbilicals!

Your baby’s intestines, which initially developed in a large swelling in the umbilical cord outside her body, now withdraw into her abdomen.