Pregnancy Week by Week

Pregnancy Week 13 – Your Baby

Size of baby at pregnant 13 week period

Your Baby

If you are now 13 weeks pregnant, your baby is between 2.5 – 3 inches in length, measuring from crown to rump. By the end of this week, your baby will weigh about 1 ounce; what a big growth spurt! Still very small, though, about the size of a kiwi and has plenty of room as he or she floats in the amniotic sac. Soon, the living quarters will become very cramped!

Your baby’s head is still very large (compared to the rest of his or her body), but it’s growth is slowing, as the body is gradually catching up. Your baby can even turn his or her large head from side to side now, because by this week, the neck is fully formed and able to support these movements.

If you have a doctor’s check-up this week, you will get to listen to your baby’s heart beat. You may have already been lucky enough to hear it, if you seen your doctor or midwife during the last couple of weeks. This is surely a very exciting event in your pregnancy! Your doctor or midwife will use a Doppler instrument, which is somewhat similar to a stethoscope (although with a stethoscope, you can’t hear your baby’s heart beat until at least 20th week). This device uses harmless sound waves (like ultrasound), which bounce off of your baby’s heart, to amplify the heart beat so you can hear it out loud. You can even buy Doppler-like devices at some stores now, but you may have difficulty finding the heart beat yourself, which can be alarming. You may be better off sticking to waiting until your monthly prenatal appointments.

At your check-up, your doctor or midwife is able to tell the difference between your baby’s heart beat and yours, because a normal heart rate for you would be under 100 beats per minute, but your baby’s is normally between 120 and 160. If you are carrying twins, it may be difficult to distinguish the two heart rates, particularly if they are very similar. If your doctor or midwife suspects he or she has heard two separate heart beats at two different places in your belly, you will probably get an ultrasound to check and see how many little ones are in there! From now on, your doctor or midwife will routinely listen to your baby’s heart beat at every prenatal visit, since it should be heard consistently now. Hearing the heart beat before now sometimes depends more on luck than anything, because the Doppler would have to be at just the right angle and, depending on if you’re very slender or heavy, it may not be heard.

Week 13, Your Body