Baby Development: The Third Month

At the third month of pregnancy, your baby has reached more milestones in development. Here are some of the developmental changes your baby undergoes in weeks 9-12.

Length and weight

By week 9, your baby measures .9-1.2 inches from crown to rump. By week 10, your baby is now officially a fetus. He/she now measures 1.25-1.68 inches and weighs a little less that 2/10 of an ounce.

By the 11th week, your baby is about the size of a large lime – measuring about 1.75 to 2.4 inches from crown to rump, and weighing about 3/10 of an ounce.

At the end of the 3rd month (week 12), your baby measures 2.5-4 inches from crown to rump and weigh about 3/10 to an ounce.

Arms and legs

Your baby’s arms and legs are longer now. During week 9, the fingers might appear swollen where the pads are forming. After two weeks the fingernails are already showing identifying characteristics. By week 12, he/she will be fully formed, finger and toenails included.


At the third month, your baby can now move his/her body and limbs. By his/her 10th week, he/she is already able to kick and swallow, though you won’t be able to feel it yet, but his/her movements can be visible during your ultrasound. By the end of this month, your baby can already open and close his/her fists and mouth.

Development of other body parts

Your baby’s head is now more erect and his neck is stronger and more developed. His/her bones start to harden. By your 10th week, the most critical part of your baby’s development has already passed.

The eyes are still covered by skin, but this will eventually split to form eyelids. His/her external ears are also formed. The ‘swooshing’ sound of your baby’s heartbeat is stronger and can already be heard using a Doppler stethoscope.

His/her external genitalia already start to differentiate and have distinguishing characteristics. But it’s still hard to tell his/her gender without genetic testing.

At the end of the third month, your baby is fully formed. All he/she has to do is continue to grow and develop. He/she already has arms; hands, fingers, feet and toes, and the beginnings of teeth start to form. Your baby’s circulatory and urinary systems should be working fine and his/her liver is already producing bile.

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