Welcome to the end of the first trimester! Week 13 is officially the last week of the first trimester, and your baby is really growing now. For many moms, the second trimester is the “happy trimester” when they enjoy glowing skin, a noticeable increase in mood and energy (especially if you experienced fatigue early on), and even increased libido. While this sounds great, and hopefully you’ll have a wonderful second trimester, do remember that every woman experiences pregnancy differently.

Your Body

Even though show time is still months off, your breasts have already begun the hard work of preparing to feed your baby. Right around this time, and definitely in the second trimester, your breasts will begin to produce colostrum. If you’re breastfeeding, this nutrient-dense fluid will be your baby’s first food for the few days of his or her life. Besides being a complete source of nutrition, colostrum is also used to help your baby’s immune system develop. There is a reason it is called “liquid gold”!

week 13 pregnancy week to week

All of that will come later, though. For now, you are still hopefully concentrating on taking care of yourself. Your uterus is now above the level of your pubic bone and you may be able to feel it.

With the symptoms of the first trimester hopefully lessening, now is a good time to take stock of your self-care during pregnancy. Have you been continuing with your prenatal vitamins? Exercising regularly and appropriately? If you’re working, are you able to take short breaks as needed?

Not too long ago, it was common to hear people say, “Well, you’re eating for two now, so go ahead and eat whatever you want!” It’s true that expectant moms are eating for two, but it might be helpful to remember that one of you is still the size of a decent-sized tomato! Throughout pregnancy, experts generally advise that women should get an extra 300 calories a day. That’s only 300 calories. To put that into perspective, a tablespoon of butter has about 100 calories. A banana also has 100 calories. Ideally, this means your 300 extra calories come from healthy sources. Think vegetables, lean proteins, and complex carbohydrates, like full grains.

There’s another good reason to be careful about your diet and weight gain. Gradual weight gain is definitely the way to go to minimize another symptom of pregnancy: stretch marks. Up to 90 percent of women develop stretch marks, and they aren’t strictly related to diet. In fact, hormones including progesterone are known to be a major cause of stretch marks. However, rapid or excessive weight gain can make your stretch marks worse. If you do develop stretch marks, the good news is that they often lessen in appearance after you deliver and over time. There is no magic cream to “cure” stretch marks, but there are things you can do, such as keeping your weight gain gradual and reasonable to lessen them.

Your Baby

your pregnancy week to week 13

Your baby’s fetal age is now 11 weeks. A typically developing baby at this stage will be approximately the size of a medium-sized tomato or lemon. It’s true that about half of this size is the head alone—babies at this stage of development have particularly large, alien-like heads. But don’t worry…his or her body will start to catch up. Within the next two months, your baby’s head will shrink from about half of the crown-to-rump length to one-third.

Around this time, one of the major changes happening is occurring in your baby’s digestive tract. Over the last few weeks, your baby’s intestines have been rapidly growing and even started to function (remember last week, when the small intestine could absorb and process sugar?). However, much of this intestinal growth has taken place outside of the baby’s abdominal cavity, with the intestines actually growing in the umbilical cord. Now, however, the intestines will begin to migrate back into the abdomen where they belong and settle into their proper place. Why do babies develop like this? It’s most likely because of the sheer size and complexity of the intestinal tract. By the time your baby is born, he or she will have 11 feet of intestines carefully packed into a cavity the size of a large apple.

Other interesting developmental changes are occurring. Your baby’s internal sex organs are now advanced. A girl fetus at this age will already have millions of eggs in her ovaries…her whole lifetime supply of eggs. And even though your baby is still months away from his or her first cry, the vocal cords are forming now.

Doctor Tip
“There are no good studies that prove that creams and treatment to prevent stretch marks actually work.”

Read more doctor tips.

Last reviewed by Jennifer Lincoln, MD, IBCLC. Review Date: November 2018


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