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The Fourth Trimester Is A Thing & Every Mom Needs To Know About It

by Jill Di Donato

When you're expecting, there's no dearth of questions running through your mind. But one that is making headlines of late had me scratching my head, and it might have you scratching yours as well. What is the fourth trimester, and how come I didn't learn about this in biology class?

Not to worry; the fourth trimester isn't when your baby can opt for an extended stay in your uterus. In fact, parenting author Sarah Ockwell Smith told The Huffington Post UK that the fourth trimester and marks your baby's transition "from womb to world." Phew, right? Actually, not so much.

Although the first three months of your infant's life will fill you with awe, Smith said that for many babies, life outside the uterus is a frightening place, and one they are "ill-prepared" for. As she explained, the womb is warm, cozy, and provides the baby inside with constant contact to the mother. Life in utero offers babies an aquatic environment with the constant muffled and soothing noise of the mother's heartbeat and digestive system (yup, those sounds are comforting to a developing fetus). Plus, a baby in utero never feels the sensation of huger or thirst, according to NBC Today. In fact, leading expert on fetal and newborn learning, Dr. Bill Fifer told Today that by week 20 of development, a baby in utero can actually taste some of the mother's cravings, which might lead to a development of favorite foods later in life. So in other words, life inside the womb is pretty great, offering a baby more than top-notch real estate, but also emotional comfort.

The fourth trimester is an interesting concept that has parenting experts speculating on the idea that the baby's brain might not be fully developed at birth, which might explain why some babies are colicky or cranky if not held, according to Parents. However, there are things that doctors and parenting experts have identified to help your baby adjust to life outside the womb during the fourth trimester. Dr. Harvey Karp, a nationally renowned expert in child development wrote a book called The Happiest Baby on the Block in which he outlined some theories to help soothe the transition from womb to world. They include the playing white noise, swaddling, holding a baby on her side, sucking on a pacifier, and swinging the baby back and forth.

As you and your baby adjust to the fourth trimester, there are definitely resources to help you and your baby get acclimated to this new time. And know, that the fourth trimester only lasts the first three months of your baby's life, according to the same article in Parents, so it's a developmental stage your baby will outgrow.