Health Library
Health Library

    1 week pregnant: Your guide to this week of your first trimester

    Updated 28 June 2023 |
    Published 24 February 2019
    Fact Checked
    Reviewed by Dr. Nazaneen Homaifar, Obstetrician and gynecologist, Inova Health System, Washington, DC, US
    Written by Kate Hollowood
    Edited by Sarah Biddlecombe
    Flo Fact-Checking Standards

    Every piece of content at Flo Health adheres to the highest editorial standards for language, style, and medical accuracy. To learn what we do to deliver the best health and lifestyle insights to you, check out our content review principles.

    From your period to hormonal changes, here’s the lowdown on being 1 week pregnant.

    Whether you’re trying for a baby or not, wondering if you might be pregnant can be a stressful time. You might be aware of classic pregnancy symptoms like nausea and a missed period, but how can you tell if you’re pregnant after what’s considered to be your first week of pregnancy? Spoiler alert: The truth is that you can’t, because pregnancy symptoms don’t actually exist this early on. That's because conception hasn’t taken place at this stage, meaning you’re not actually pregnant yet, which can be more than a little confusing!

    Keep reading to learn more about what’s likely to be happening in your body at 1 week pregnant, with insight from Dr. Jenna Flanagan, academic generalist obstetrician and gynecologist, Massachusetts, US. 

    Your pregnancy at 1 week

    Let’s start with a look at how the weeks of your pregnancy are counted. Technically speaking, at 1 week pregnant, you’re not actually pregnant yet. This means that you can’t tell if you’re pregnant in your first week of pregnancy — you would only be considered 1 week pregnant in hindsight. 

    Confused? We hear you. Let’s break this down a bit. Gestational age and fetal age are actually two different things. Your gestational age — or how long you’ve been pregnant — is calculated from the start of your last period. In comparison, the fetal or conceptional age is the actual age of your baby. So when we talk about being 1 week pregnant, we’re referring to your gestational age. 

    “Pregnancy is dated by the first day of the previous menstrual cycle prior to diagnosis of pregnancy,” explains Dr. Flanagan. “Therefore, the first week of pregnancy is before ovulation. This is the first week of the follicular stage (the phase of the menstrual cycle when an egg is maturing), which happens before an egg is released from the ovary and fertilization happens.” 

    Counting your pregnancy week by week in this way can definitely feel confusing at first. But don’t worry, if you do become pregnant, it will feel more natural as you go on. And don’t forget that you can also figure out when your baby might arrive using our handy due date calculator.

    It’s worth noting that if you have irregular cycles (which means your cycle length varies by more than seven to nine days), then dating your pregnancy from your last period can be tricky. As Dr. Flanagan explains, “If the cycles are irregular, often dating by the first day of the last menstrual cycle can be inaccurate or misleading.” Why? “Because ovulation occurs at vastly different times in people who have irregular cycles,” she says.  

    Don’t worry, though. This simply means you may need to confirm your exact pregnancy dates through an early ultrasound scan once you’re a bit further along in the first trimester. “Blood hormone levels can give a general idea of which week of pregnancy you’re at,” explains Dr. Flanagan. “But an early ultrasound can then confirm the dating of the pregnancy. This typically occurs between 5 to 7 weeks.” However this ultrasound can also be done slightly later, up to 13 weeks of pregnancy.

    Your body at 1 week pregnant

    Too early for pregnancy symptoms

    As you’re not technically pregnant yet, it’s too soon for any early signs of pregnancy. But that doesn’t mean there isn’t anything happening! This week, your body will be shedding the lining of the uterus through your vagina, causing the bleeding that you know as your period. 


    For the next few days, you might continue to experience symptoms of premenstrual syndrome (PMS) from your previous cycle, such as tiredness, bloating, headaches, and mood swings. We know how draining these can be, but it might bring a little comfort to know that if you do experience them, you’re certainly not alone. In fact, more than 90% of women say they get some PMS symptoms, which are caused by falling levels of estrogen and rising levels of progesterone after ovulation.  

    Want to know more?

    Download the Flo app for tailored insights throughout your pregnancy

    Your questions answered

    When do pregnancy symptoms start?

    Pregnancy symptoms tend to start between 4 and 6 weeks. One of the earliest signs of pregnancy is having a missed period, but this can be difficult to recognize if you have an irregular cycle. It’s also possible to mistake implantation bleeding for your period, which can happen at 3 weeks pregnant, or around 10 to 14 days after conception.

    While it’s possible to conceive and not experience many of the typical early symptoms of pregnancy, it’s always a good idea to know what to keep an eye out for. With that in mind, other early pregnancy symptoms to look out for further down the line include things such as tender or swollen breasts, fatigue, needing to pee more often, and nausea with or without vomiting. 

    If you experience any of these, it’s natural to wonder whether they’re a sign of PMS or pregnancy. Just to confuse matters even further, PMS symptoms also include things like breast tenderness and tiredness. If you’re finding it all a bit, well, bewildering, then remember that many women feel the same way. It can help to continue to track your cycle using an app like Flo, and to try to relax and be patient — as hard as this can be. 

    When should I take a pregnancy test?

    The best time to take a pregnancy test is the first day of your missed period. This is because at-home pregnancy tests work by detecting the pregnancy hormone human chorionic gonadotropin (hCG), which your body starts to produce around 6 days after fertilization. 

    However, tests can become more accurate a few days after the first day of your missed period, with your hCG levels doubling about every two days in the first few weeks of pregnancy (yes, really!). It can be super frustrating having to wait until then, but it’s the best way to get the most accurate result and avoid getting a false negative — we promise!

    If your cycle is irregular, it can be best to do the test at least 21 days after you had unprotected sex. But don’t hesitate to ask your health care provider for advice if you feel you need more guidance. 

    Should I feel different?

    As we’ve seen, pregnancy symptoms at 1 week don’t technically exist, as you’re not actually pregnant yet. So you shouldn’t feel any different from how you might normally feel at the start of your cycle. Of course, if you’re trying to conceive this month, you may feel a sense of anticipation, excitement, or even anxiety. You might feel a whole mix of emotions! Just know that all of those feelings are completely normal, and you’re definitely not alone. 

    1 week pregnant checklist

    Experts recommend taking at least 400 mcg of folic acid a day for one month before you get pregnant and up until you are 12 weeks pregnant. This is because folic acid decreases the risk of your baby developing a neural tube defect, which can affect their developing brain, spine, or spinal cord.

    Ideally, experts say you should start taking folic acid three months before you plan to get pregnant. “Starting a prenatal vitamin and folic acid prior to actually conceiving is important because the generation of the spinal cord occurs very early in the pregnancy,” explains Dr. Flanagan. “The goal is to have an adequate folic acid store before this development occurs, otherwise the pregnancy is at higher risk for neural tube defects (the neural tube is the primitive spinal cord that develops during the third and fourth week of the pregnancy, prior to many people knowing that they are pregnant).”

    However, if you haven’t started taking folic acid yet, or if you find out you’re pregnant unexpectedly, don’t worry. You can’t plan for everything in life! Just start taking the supplement as soon as you can. 

    When to consult a doctor at 1 week pregnant

    At 1 week pregnant, you’re not technically pregnant yet, so you don’t need to see a doctor this week. You should first get in touch with your health care provider as soon as you get a positive pregnancy test, which likely won’t happen until you’re about 4 weeks along. 

    1 week pregnant: The takeaway

    You’re at the start of a new cycle, which means there’s a new chance you might get pregnant. It’s natural to feel anxious or excited — or even both at the same time! While you don’t have any pregnancy symptoms to look out for just yet, getting your period marks the start of a process that could lead to pregnancy. The best thing you can do for now is stay in tune with how you’re feeling and, if you can, try to relax.


    “Doing a Pregnancy Test.” NHS, Accessed 24 May 2023.

    Edwards, Kenia I., and Petr Itzhak. “Estimated Date of Delivery.” StatPearls, StatPearls Publishing, 2022.

    Curran, Mark A. “Fetal Development.”, Accessed 24 May 2023.

    “Follicular Phase.” Cleveland Clinic, Accessed 24 May 2023.

    Gao, Mingzhou, et al. “Global and Regional Prevalence and Burden for Premenstrual Syndrome and Premenstrual Dysphoric Disorder: A Study Protocol for Systematic Review and Meta-Analysis.” Medicine, vol. 101, no. 1, Jan. 2022.

    “How and When to Take Folic Acid.” NHS, Accessed 24 May 2023.

    “Implantation Bleeding: Common in Early Pregnancy?” Mayo Clinic, 19 Apr. 2022,

    “Menstrual Cycle.” Cleveland Clinic, Accessed 24 May 2023.

    “Menstrual Cycle: Animation.” NHS, Accessed 24 May 2023.

    “Methods for Estimating the Due Date.” The American College of Obstetricians and Gynecologists, May 2017,

    “Neural Tube Defects (NTDs): What They Are, Causes & Prevention.” Cleveland Clinic, Accessed 24 May 2023.

    “Nutrition during Pregnancy.” The American College of Obstetricians and Gynecologists, May 2023,

    “Planning Your Pregnancy.” NHS, Accessed 24 May 2023.

    “PMS (Premenstrual Syndrome).” NHS, Accessed 24 May 2023.

    “Pregnancy Test: When to Take, Types & Accuracy.” Cleveland Clinic, Accessed 24 May 2023.

    “Premenstrual Syndrome (PMS).” Mayo Clinic, 25 Feb. 2022,

    “Signs and Symptoms of Pregnancy.” NHS, Accessed 24 May 2023.

    “Symptoms of Pregnancy: What Happens First.” Mayo Clinic, 3 Dec. 2021,

    “Your NHS Pregnancy Journey.” NHS, Accessed 24 May 2023.

    History of updates

    Current version (28 June 2023)

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

    Published (24 February 2019)

    In this article

      Try Flo today