First-trimester pregnancy symptoms: What to expect and why

    Updated 19 June 2023 |
    Published 25 February 2019
    Fact Checked
    Medically reviewed by Dr. Sara Twogood, Obstetrician and gynecologist, Cedars-Sinai Medical Group, California, US
    Written by Carly Lewis-Oduntan
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    You might be familiar with many of the first-trimester pregnancy symptoms. But why are they happening, and what exactly is going on in your body during the first few weeks of pregnancy? A Flo expert explains it all.

    Nausea, cramping, and a strange metallic taste in your mouth that you just can’t shake — the first trimester of pregnancy can be a wild ride. And while your health care provider may have given you a trusty list of symptoms to expect, you might be curious as to why they’re happening. With so many fascinating changes, what exactly is going on in your body week by week during your first trimester

    Throughout your pregnancy, your body is working overtime to help to create a tiny new human.  It’s no small feat, and no two pregnancies are exactly the same. 

    “There are some symptoms that can be more common in one trimester than the other, but there’s nothing that’s 100% in the first trimester only,” says Dr. Charlsie Celestine, obstetrician and gynecologist, New Jersey, US. “Everybody’s a little bit different.” 

    To help you figure out which symptoms you might experience in your first trimester — and, more importantly, why — Dr. Celestine explains everything you might expect in your first few weeks of pregnancy. 

    First pregnancy trimester: What can you expect?

    It might start with your boobs feeling swollen or perhaps more tender than usual. A nap in the middle of the day may have become essential rather than a little treat. And your period tracking app might have notified you that your period is late. So, what now? 

    If you think you’re experiencing symptoms typically associated with pregnancy, then the best thing to do is to take a pregnancy test. And if it comes back positive, reach out to your doctor. They will ask about your medical history and any previous pregnancies you’ve had. They’ll also ask you the date your last period started, so they can calculate the exciting part: your due date. Apps like Flo can help you track your cycle and your last period to make that a little bit easier.

    When might you spot the first signs of pregnancy? 

    Ideally, you’ll have your first prenatal appointment within the first 10 weeks of your pregnancy. However, you might have started experiencing first-trimester symptoms long before that. They can begin as early as 10 days after a baby is conceived. Alternatively, you might not have had any pregnancy symptoms yet, aside from missing your period. Everyone is different. 

    At first, you might have noticed implantation bleeding — light spotting of blood that happens when a fertilized egg attaches to the lining of the uterus. This usually happens around day 10 to 14 after you’ve conceived, around the time you’d normally have your period. 

    Unless you’ve been trying to conceive and have been tracking when you ovulate, you might not recognize implantation bleeding for what it is and might think it’s a light period. That’s quite common, although you’ll soon realize it’s not a proper period. Implantation bleeding is never enough to fill a pad or tampon and will typically stop by itself. 

    As your first trimester progresses week by week, there are a number of symptoms you might experience. And they can be an indication of the amazing processes that are happening within your body. 

    Common first-trimester pregnancy symptoms

    Pregnancy symptoms can really vary from person to person and pregnancy to pregnancy. There’s no way you can predict how your first trimester will leave you feeling. One study of 136 people who were trying for a baby found that 50% of people had some pregnancy symptoms within five weeks after their last period. 90% reported some symptoms by the end of eight weeks.

    So, noticing new symptoms with pregnancy is very common. But should you believe the myth that you can guess the sex of your baby based on the headaches, sickness, and cravings you have during your first trimester?

    Some research has shown that people who have extreme nausea and vomiting (a pregnancy condition called hyperemesis gravidarum) are more likely to be pregnant with a baby girl. It’s been suggested that this might be due to differences in your human chorionic gonadotropin (hCG) levels. This is the hormone that you produce starting in the first few weeks of pregnancy thanks to your placenta. However, there is very little medical evidence to suggest your hCG levels can predict if you’re having a boy or a girl

    Despite this, knowing what symptoms to expect can provide some comfort. At least then, you can prepare with pregnancy-friendly pain relief. But you might be curious as to why you’re experiencing these symptoms. 

    So let’s get into it. What are some first-trimester symptoms you might expect, and why do you have them?

    Missed period

    You’ve seen it in the movies and probably spoken to your friends about it, but there’s a reason why a missed period is so often thought of as the most obvious sign that you’re pregnant. 

    After you’ve conceived and the fertilized egg has implanted in your uterine wall, your body continuously releases the hormones progesterone and estrogen. Because of these changes in your hormone levels, your ovaries will stop releasing eggs (ovulation) while your baby grows and your pregnancy develops. This means that your menstrual cycle pauses, and you won’t have another period until after your baby is born. 

    However, a missed period isn’t automatically a sign of pregnancy. You might miss a period due to any number of things. It could be thanks to changes in your hormones and cycle, stress, or changes in your exercise regime and lifestyle. If you could use a helping hand monitoring how regular your cycle typically is and spotting any changes, try using an app like Flo.

    Spotting 

    You might not have expected it, but you might experience some spotting (light bleeding) during your first trimester. This could be for a couple of different reasons. 

    As we mentioned above, if you notice light bleeding or brown discharge (creamy, white discharge mixed with blood) 10 to 14 days after you’ve conceived, then it could be implantation bleeding. 

    If you experience spotting at any other time, this isn’t because of implantation. However, it could be caused by penetrative sex and changes to your cervix, which could cause a little bit of bleeding. It might also be caused by bleeding behind your placenta.

    Understandably, you might be concerned if you notice blood (like spotting) in your underwear, especially after finding out that you’re pregnant. Generally, light spotting stops on its own, and as long as there’s no other pain, discharge, or burning when you pee, it probably isn’t something to be too worried about. But if you’re also experiencing cramps, bleeding quite a lot, or if you’re simply concerned and would like to put your mind at ease, it’s always wise to reach out to your health care provider. 

    Light cramping

    You might notice some mild cramps in the early stages of pregnancy. This is fairly common and often harmless; it’s likely just the embryo attaching to your uterine wall. There’s a lot going on in there, remember! However, if the cramping goes on for a few days, becomes more painful, or you’re worried, speak to your doctor. 

    Tender boobs 

    Tender boobs or sensitive nipples are another early sign of pregnancy, and this one can be pretty easily explained. After you’ve conceived, your body releases a surge of the hormones estrogen, progesterone, and prolactin — the last of which helps your body to create breast milk. These hormones can impact the way your boobs look and feel. You might feel tenderness and tingles and may notice that your nipples and areolas (the skin around your nipples) look darker. 

    Nausea and vomiting

    Morning sickness may be a term you’ve frequently heard used in the media or perhaps your doctor’s office. But it’s actually a very inaccurate misconception. During your first trimester, you might feel nauseous (or actually vomit) morning, noon, and night. It’s estimated that around 70% of people experience pregnancy nausea and vomiting, and it can start as early as week four. 

    No matter how common pregnancy nausea is, it doesn’t make it any less unpleasant. Some studies have linked nausea during your first trimester to your hormones. As we mentioned above, your body produces hCG in the first few weeks of pregnancy. It’s produced by your placenta.  

    Research has found that people with higher levels of hCG are more likely to experience nausea and vomiting during their first trimester. However, there’s still fairly limited information out there as to why that is. 

    If you’re vomiting multiple times throughout the day and struggling to keep your food and drink down, then it could be a sign that you’ve developed hyperemesis gravidarum (also known as HG). HG is essentially extreme nausea and vomiting during pregnancy and only affects between 1% and 3% of pregnant people. Many people with HG require medical attention. 

    Extreme nausea can be incredibly difficult to live with. You might feel that you can’t enjoy your first trimester or do any of the things you were so looking forward to. It’s important to know you’re not alone. Organizations like the HER Foundation and Pregnancy Sickness Support are raising awareness about hyperemesis gravidarum and support people experiencing it.  

    Tiredness

    Alongside not feeling well, you might be able to blame those midafternoon naps on hormone changes, too. Fatigue in pregnancy can be real.

    During the first trimester, your baby is growing and changing much faster than you might think. Stanford University describes this as the time the “most dramatic changes and development happen.” And there are a lot of changes going on in your body that can cause fatigue. 

    Ready for the science behind it? To support the incredible development of your baby, progesterone levels rise dramatically. That ensures that your uterus lining is thick and healthy so your embryo can attach properly, and it also relaxes the muscles in your uterus so they don’t contract until you give birth. 

    However, all of these hormonal changes can affect how tired you feel. That’s because progesterone doubles as the brain’s calming hormone — it helps you to sleep. As your progesterone levels rise and stay high in the first trimester of pregnancy, that’s why you’re so tempted to reach for the blanket by 7 p.m. 

    Headaches

    Headaches are fairly common during the first trimester of pregnancy. After conception, your estrogen levels rise, and the change in your hormone levels can bring on a headache. Similarly, if you’ve been feeling nauseous or dehydrated, you may get a headache. 

    Headaches are never pleasant, and if you’ve noticed you’ve become much more susceptible to them during your first trimester, there are some things you can do to ease the pain: 

    • Drink plenty of fluids and try to stay hydrated. 
    • Try to get at least eight hours of sleep at night.
    • Rest and relax — you could try a pregnancy yoga class, for example.

    If you experience strong headaches that you just can’t shake, then speak to your health care provider about pregnancy-safe over-the-counter medication that may help. 

    Needing to pee a lot more

    One symptom that often goes untalked about is the constant need to pee. You find out you’re pregnant, then BAM! Suddenly you can’t make it through a movie without pressing pause for at least three bathroom breaks. 

    Not everyone experiences this in the first trimester, but for those who do, it can be explained by the fact that you have a lot more blood rushing around your body. As your blood supply increases, your kidneys have to work extra hard to filter it and remove any impurities. These leave your body in the form of urine, so the more blood you produce, the more you’re going to need to pee.

    If you notice any discomfort while you’re using the bathroom or the urgency to go is severe, then you should reach out to your health care provider. 

    Acne

    You might have thought that you’d seen the end of acne when you finished puberty, but pregnancy acne is a very real phenomenon. It’s caused by an increase in oil (also called sebum) on your skin as a result of — you guessed it — hormones! 

    With everything else that’s likely going on during your pregnancy, acne can feel like the last thing you need. Let’s be honest — it’s not fun. If you’re concerned about how your skin texture has changed throughout your pregnancy, then don’t be afraid to reach out to your health care provider. 

    Mood swings

    Mood swings are another symptom that you might link to premenstrual syndrome but can really impact you when you’re pregnant. This is because both your cycle and pregnancy are full of hormonal changes

    A 2021 study noted that pregnant women “often experience the highest euphoric, irritable, and depressed moods in early pregnancy.” Yeah, it can be a roller coaster. This is due to the fact that your body is adapting to much higher levels of estrogen and progesterone. Plus, you may be grappling with a whole host of other pregnancy symptoms. It’s natural for it to get you down. 

    If you’re struggling with low moods during your pregnancy, look for support from loved ones or your doctor. You’re going through a major life change, and they may be able to offer you some help or at least a shoulder to lean on.

    Unexpected pregnancy symptoms in the first trimester 

    Along with the more common early signs of pregnancy we’ve covered above, your first trimester may also be filled with some weird and wonderful symptoms that you weren’t expecting. Such as …

    Nasal congestion 

    Have you been blowing your nose a lot more or noticed you can’t breathe through your nose as clearly as you used to? You’re not alone. Congestion or a blocked nose is thought to affect up to 20% of pregnant people. 

    This could be related to the fact that as your blood volume has increased, the glands in the tissue that lines your nasal passage become more active. As a result, you might feel like you have a stuffier nose. Bet you weren’t expecting that from pregnancy.

    If you start to feel pressure in your face or have a fever and flu-like symptoms, speak to your health care provider.

    Metallic taste in your mouth 

    Are you wondering why your cherished first cup of coffee in the morning now tastes like a bag of coins? This could be one of the more surprising changes that happen during your pregnancy. 

    Research has found that many people experience a change in their sense of taste or smell during pregnancy. One study found that all of the pregnant people they spoke to noticed some change. The medical name for this is dysgeusia. It’s caused by your rising hormones as your body adapts to your new pregnancy. As they start to settle down, you should notice your taste returning to normal, too.

    When do first-trimester pregnancy symptoms stop? 

    Finding out you’re pregnant can be incredibly exciting. But if you’re tackling headaches, nausea, and changes in your mood, you might be curious as to when your first-trimester symptoms will stop. 

    Everyone is different here,” says Dr. Celestine. “Some feel their first-trimester symptoms until the delivery of the baby, but for the majority of people, these improve or resolve by the second trimester (around week 14).

    When should you seek medical help? 

    Your first trimester is a time of massive change and excitement. But if you feel on high alert week by week to every new twitch, pain, and wave of nausea, that’s also totally understandable. You won’t see your baby for the first time until your first scan and may find you need a bit of extra reassurance before then.

    If you’re worried about the severity of your pregnancy symptoms — or lack thereof — know that your health care provider is always there.

    “The symptom I always tell people to seek help [for] is severe pain,” advises Dr. Celestine. “I like to say, ‘If you’re doubled over in pain, or if the pain is stopping you from doing activities, then it’s severe.’ Or if you have vaginal bleeding — like a period flow of blood — that’s concerning, so we’d need to check that out.”

    • Other symptoms to look out for include: 
    • A fever exceeding 100.4 F (38 C)
    • Fainting and dizziness
    • Continuous vomiting or diarrhea 
    • Sudden swelling of one of your legs or arms, causing ​​it to feel heavy and ache (look out for red or warm skin in the affected area)

    First-trimester pregnancy symptoms: The takeaway 

    The first trimester is a monumental time. “Your body is building a human being from scratch,” says Dr. Celestine. And it’s a big deal. So while the symptoms aren’t always the most pleasant, and you may not be feeling your best all of the time, generally, it’s just what your body needs to do to keep growing your baby.

    Thankfully, most people report feeling better during the second trimester. So if nothing else, you’ve at least got something to look forward to just around the corner. If at any point you’re worried about your first-trimester symptoms or you need some reassurance, don’t be afraid to reach out to your health care provider. They’ve heard it all before and will be well equipped to put your mind at ease. 

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    History of updates

    Current version (19 June 2023)

    Medically reviewed by Dr. Sara Twogood, Obstetrician and gynecologist, Cedars-Sinai Medical Group, California, US
    Written by Carly Lewis-Oduntan

    Published (25 February 2019)

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