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18 Weeks Pregnant: Baby Update

Your baby is developing their sleep and wake cycle—and they don't even need an alarm clock to do so! They may even have a favorite sleeping nook…like on top of your bladder. Babies spend lots of the time in the womb snoozing, but when your little one is awake, you're probably starting to feel it! They're getting bigger and stronger, so kicks—that felt like little flutters a few weeks ago—now pack some punch.

Your baby's eyelids are still fused shut but they have started little blink-like movements. Their nervous system continues to develop, and their nerves are gradually being wrapped in a wonderful protective coating of myelin, a thin fatty layer…like insulation around a copper wire. Fat is also increasingly covering their entire skinny frame. (And, they're developing a very important little collection of “brown” fat.) Like an internal candle, this special fat will be slowly “burned up” to keep them warm after they're born into the chilly world…

Did you know all babies—regardless of sex—start out with labia? But now, little girls have the uterus and fallopian tubes in place. And boys have penises, but the testes have not slid all the way down into their little sack. (For some boys, it will take months—even years—for the testes to descend into the scrotum.)

18 weeks pregnant is how many months?

18 weeks pregnant is more than 4 months along.

Baby’s Size at 18 Weeks

At 18 weeks, your sweet baby is about as big as a sweet potato!

18 Weeks Pregnant: What to Expect

Now that you’re definitely into the second trimester, it’s time to move past sheer survival and on to maximizing your health. You may finally be regaining a taste for veggies and proteins after months of just craving carbs and you’re probably feeling a bit more inclined to exercise, now that you have more energy. 

Another healthy step to start planning is to get vaccinated. Tdap and flu vaccines are recommended for all pregnant people—both have been proven safe for pregnancy. 

Influenza can be much more dangerous to pregnant people and their babies than to those who are not pregnant. So, if you’re pregnant during flu season, your OB or midwife will advise getting a flu shot as early as possible.

You can wait a while on the Tdap. It’s given during the third trimester. (It’s also smart to plan to protect your vulnerable little baby by giving this booster to everyone who will be in close contact with your newborn.) Tdap protects against tetanus, pertussis (whooping cough) and diphtheria. Through you, it will help protect your baby from the pain and danger of whooping cough—until they get their first vaccines at 2 months. In fact, a 2021 study published in Pediatrics found that both the flu shot and pertussis vaccine effectively prevented these diseases in babies under 2 months! 

18 Weeks Pregnant To-Do List

  • Discuss your fears with your care provider: Are you worried about gaining too much weight? Birth defects? Pain during labor? EVERY expecting parent has doubts and concerns, so don’t keep them hidden in the shadows! Make a list of topics to discuss with your provider at your next appointment. The sooner you start talking about your big worries…the smaller they will get.

  • Start writing a birth plan: This is a good time to start talking with your spouse to create a list of your preferences for labor, delivery and those first days as a mom. You might want to include pain management like hypnobirthing, epidural, or laboring in water. And, consider your preferences when it comes to having adoula, delayed cord clamping, skin-to-skin time, keeping the baby with you for a few hours after birth, baby’s eye medication, etc.

    To make it easy, check out our guide to writing a birth plan—which includes free sample birth plans and templates to get you started. Once you’ve drafted your birth plan, bring it in to review with your OB or midwife. (Note: It’s super important to remember that giving birth is something you can plan…but not control. Sometimes medical complications arise and big parts of your plan may have to be thrown out the window. That’s normal…flexibility is an important trait for all parents!)

  • Protect your family…in case of bad things: Make sure to have fire insurance and a smoke alarm. With a new baby will come even more adult responsibilities! Like drafting a will and buying life insurance. Now is the time to start thinking about all the ways you want to make sure your little family is taken care of. While you’re at it, you might want to plan whom you would want to be the guardian of your child...just in case. (You don’t want anyone else making that decision.)

Pregnancy Quote of the Week

"The moment a child is born, the mother is also born. She never existed before. The woman existed, but the mother, never. A mother is something absolutely new." —Rajneesh

17 Weeks Pregnant | 19 Weeks Pregnant

About Dr. Harvey Karp

Dr. Harvey Karp, one of America’s most trusted pediatricians, is the founder of Happiest Baby and the inventor of the groundbreaking SNOO Smart Sleeper. After years of treating patients in Los Angeles, Dr. Karp vaulted to global prominence with the release of the bestselling Happiest Baby on the Block and Happiest Toddler on the Block. His celebrated books and videos have since become standard pediatric practice, translated into more than 20 languages and have helped millions of parents. Dr. Karp’s landmark methods, including the 5 S’s for soothing babies, guide parents to understand and nurture their children and relieve stressful issues, like new-parent exhaustion, infant crying, and toddler tantrums.

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Disclaimer: The information on our site is NOT medical advice for any specific person or condition. It is only meant as general information. If you have any medical questions and concerns about your child or yourself, please contact your health provider.