In Depth Baby Product Reviews Led by a Pediatrician

Your Fetus' Maturing Systems

Your little one's systems are busy kicking into high gear
Your Fetus' Maturing Systems
A medical model of a 12 week old fetus in utero
Credit: Sebastian Kaulitzki ©
Saturday September 28, 2019

Week 12 marks something of a milestone for your fetus; your little one is about 2 inches from head to bottom, and she weighs around one-half of an ounce, having more than doubled in size in the last three weeks! She is about the size of a lime or small plum. While all fetuses follow the same developmental pathways, it is around this week (heading into the second trimester) that each fetus will begin growing at its own pace based on genetics and other factors.

Around this week, the development of new systems and parts will stop, and the maturation process will begin. During this time of growth, the organs will mature rapidly with kidneys that can excrete urine to the bladder, muscle contractions of the digestive system complete with the migration of the intestines from the umbilical cord to the abdomen, and hormone production in the pituitary gland. The bone marrow is also making white blood cells now that will help fight the germs the baby encounter once they move to the outside world.

Reference Sources

  1. American Pregnancy Association - Pregnancy Week 12
  1. Mayo Clinic - Pregnancy week by week
  1. WebMD - Your Pregnancy Week by Week 9-12

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