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Guide to Being 31 Weeks Pregnant

What's Going on In Your Body

Length: About 16 inches (head to toe). Weight: More than 3 pounds. Fat: Building up.

Deep in your uterus, a baby is transforming, in the final stages of becoming someone who can live outside your womb. Some of the goings-on this week can include:

  • A rhythmic wake/sleep cycle
  • Dramatic brain development, forming what will eventually be about three trillion brain-body connections
  • Fully operational senses (all five)
  • Continued lung development
  • Reproductive-system development (descending testicles or a visible clitoris)

One of the big ones this week is the formation of baby fat. It's starting to fill in beneath the skin -- so while your little one is still pretty scrawny, he or she is finally starting to plump up, which also has the effect of making baby's skin less saggy. Fetal weight gain from fat will be dramatic over the remainder of your pregnancy.

And as mom facilitates all this growth and development, her partner is playing a different but similarly important role …