13 weeks pregnant: Your guide to this week of your first trimester

    Updated 18 August 2023 |
    Published 24 February 2019
    Fact Checked
    Reviewed by Dr. Nazaneen Homaifar, Obstetrician and gynecologist, Inova Health System, Washington, DC, US
    Written by Christina Quaine
    Edited by Sarah Biddlecombe
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    From your baby’s development to why you need to pay attention if your gums are bleeding, here’s the lowdown on being 13 weeks pregnant.

    Genitals! Urine! Lemons! It’s all happening now that you’ve hit 13 weeks. This is the final week of your first trimester, so you’ll soon be heading into your second trimester. And if you’re wondering how many months are 13 weeks pregnant, you’re into your fourth month of pregnancy now. 

    As you mark this milestone, let’s dive into what to expect and look out for this week with the help of a Flo expert.

    Your baby at 13 weeks pregnant

    Their genitals are developing

    Your baby’s testes or ovaries are now fully developed inside, and a penis or clitoris is still growing. That means by the time you have your 20-week ultrasound, your doctor should be able to see the sex of your baby on the screen — although you might find it difficult to figure out what you’re looking at! 

    Their kidneys have developed 

    By now, your baby’s kidneys have also developed. What’s more, your baby is even beginning to produce urine. And their pee plays a vital role in your pregnancy because, by 20 weeks, it makes up most of your amniotic fluid — the liquid that your baby floats around in to protect and cushion them in your uterus. 

    How big is a baby at 13 weeks?

    Length (crown to rump): Around 6.7 cm or 2.6 in.

    Weight: Around 73 g or 2.6 oz.

    Size: Equivalent to a lemon

    All measurements are approximate and vary within the normal range.

    Your body at 13 weeks pregnant

    No more nausea? 

    You may be saying goodbye to pesky first-trimester symptoms like nausea and vomiting right about now. Hurrah! The reason? Research suggests these symptoms might be caused by the effects of the pregnancy hormone, human chorionic gonadotropin, which is produced by your placenta shortly after you conceive. “By this stage of pregnancy, your levels of this hormone have peaked, and they sometimes drop a little bit, too, which can make you feel better,” explains Dr. Jenna Flanagan, obstetrician and gynecologist at Beth Israel Deaconess Medical Center, Massachusetts, US.

    You may be noticing gum changes 

    If you’re finding that your gums are sore, swollen, and/or bleeding, it may be thanks to pregnancy gingivitis (gum disease). Again, this is likely due to hormonal changes during pregnancy. These can make you more likely to get plaque (that sticky layer containing bacteria that forms on your pearly whites) — and that leads to inflammation and bleeding. In fact, around 60% to 75% of pregnant women develop gingivitis, so now is a good time to book a trip to your dentist for a checkup.

    Your questions answered

    Can you feel your baby move at 13 weeks?

    While your baby is certainly active down there in your uterus, it’s too early for you to feel any of their movements. But you won’t have to wait much longer before that first magical moment, as you should first feel movement between around 16 and 24 weeks pregnant. Did you know that the first time you feel your baby move has a name? Yep, it’s called quickening

    Should you have a bump at 13 weeks pregnant?

    You might; you might not — there are no hard and fast rules about this, as every pregnancy is different. “Whether you have a bump yet can depend on different things such as whether you’ve been pregnant before or if you’re expecting more than one baby — in those cases, you might show earlier,” explains Dr. Flanagan.

    What might a 13-weeks pregnant belly look like?

    So what might you expect if you have started to show? “You may have a small baby bump by now as your uterus has grown up and out of your pelvis — so now might be the time to buy some stretchy maternity clothes, like pants,” adds Dr. Flanagan. 

    Is 13 weeks the first or second trimester?

    The American Congress of Obstetricians and Gynecologists defines the first trimester as up until 13 weeks and six days. “Thirteen weeks is a transition point in your pregnancy when, hopefully, you’re over the worst of your symptoms, and you may have more energy,” says Dr. Flanagan.

    Want to know more?

    Download the Flo app for tailored insights throughout your pregnancy

    Your 13 weeks pregnant checklist

    Ensure you’re eating well 

    So, what should be on your pregnancy food list at 13 weeks pregnant? Dr. Flanagan has this advice: “Eat what your body needs. If you’re hungry, eat. If you’re not hungry, you don’t have to force yourself to eat additional calories. Eating small, frequent meals throughout the day is a good idea to keep your energy levels up.” So essentially: listen to your body. You’ve got this! 

    Think about changing your sleeping position

    It might sound weird, but you could also add changing your sleeping position to your pregnancy checklist. This is all about what’s comfortable for you, says Dr. Flanagan. “At this stage, if you feel comfortable sleeping on your back or on your stomach, that’s fine. It’s not dangerous for you or your baby,” she says. “Starting from about 20 weeks, I usually tell people to avoid sleeping flat on their back. That’s because by then, your uterus is heavy enough to press on your abdomen’s major arteries and blood vessels. The result is you can feel light-headed and nauseous because of the decrease in blood flow.” Of course, it can be difficult to control your body’s position when you’re asleep. So if you wake up on your back, don’t panic — simply roll over and go back to dreamland.

    When to see your doctor at 13 weeks pregnant

    At 13 weeks pregnant, you can check in with your doctor about what to expect during your second trimester. Exciting! And remember that you don’t need to wait until your appointments if you have any concerns or questions about your pregnancy. However, at 13 weeks pregnant you should contact your doctor immediately if you experience: 

    This isn’t an exhaustive list and just an example of some of the changes you should look out for. Some of these can be a sign of miscarriage or other health complications, so it’s essential that you speak to your doctor about the best next step for you. And if you’re ever worried about any other symptoms you experience during pregnancy, then don’t hesitate to reach out to your healthcare provider. 

    13 weeks pregnant: The takeaway

    At 13 weeks pregnant, you’re on the final stretch of your first trimester. Nausea and vomiting should (finally!) start to ease by now, and you might even begin to show a baby bump. And what about your little one? Well, at 13 weeks, your baby’s genitals are developing, and they’re even starting to pee. While you’re unlikely to be able to feel their movements at this stage, you won’t have long to wait. So relax and enjoy these few days before you enter your second trimester.


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    History of updates

    Current version (18 August 2023)

    Reviewed by Dr. Nazaneen Homaifar, Obstetrician and gynecologist, Inova Health System, Washington, DC, US
    Written by Christina Quaine
    Edited by Sarah Biddlecombe

    Published (24 February 2019)

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