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Your First Trimester: Everything to Expect

Updated: Oct 12, 2023

Your pregnancy journey will fly by. You may be wishing it away, as you’re just so desperate to meet your little one at the end of the journey – but you’ll look back at it and wish you’d savoured every minute. Even that pesky first trimester!

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So, what can you expect from your first trimester? Well, human pregnancy is split into three, distinct, periods called trimesters, and each one lasts for 12 weeks in a normal run pregnancy. Of these, the first one – running from conception to week twelve (approximately three months) is the one that tends to have the most impact on people. When you think about it, that makes sense. Afterall you’re going from being not pregnant to well … pregnant!

Sure, the last trimester and the birth of your baby can be pretty surprising, particularly when baby finally arrives, but by that time, you are usually ready for just about anything. When it comes to surprises and a steep learning curve, the first trimester is hard to beat. But don’t panic! We’ve got you covered, so you can be prepared to make your first trimester as comfortable and breezy as possible!

It’s very common to not be instantly be aware that you’re pregnant, unless you’ve been meticulously planning it, it could be several weeks before you know. You may have even started to feel some of the symptoms that are normal during your first trimester. What happens in these first few weeks are your baby will have grown from a tiny egg, to as much as two inches long. By 5 weeks old your little one will just about have a detectable heartbeat and if you choose to go for an early reassurance scan – you’ll be able to hear it. But it isn’t just your baby that will be going through some changes, your own body is going to experience a whole raft of ups and downs, ins and outs and general shifts to adapt to carry your little for the next 9 months. If this is your first pregnancy, relax and find sanity in the knowledge of all the other women that go through the same thing, it will be a roller-coaster, especially the first trimester, but it will be so worth it when you get to hold your baby at the end.

Some changes you might experience

So, what can you expect in your first trimester? Well, for a start your body is going to begin to adapt to the fact that you are going to have a baby, and there will be a certain number of physical changes that will occur. Some of these will slowly creep up on you while others might happen suddenly and might actually be your first indication that you are pregnant in the first place. So, what are the common physical changes that a woman’s body undergoes when you become pregnant?

Morning sickness

Definitely one of the first and definitely one of the most notorious! This can be one of the first indications of pregnancy and is bought on by the chemical and hormonal changes that your body undergoes as it starts to prepare for the growth of your baby inside you. Morning sickness is a nauseous feeling, usually accompanying actual vomiting, that occurs during pregnancy, and usually quite early on in it too.

Despite its name, morning sickness can actually strike at any time of the day or night but is predominately experienced in your waking hours. Morning sickness isn’t usually a problem and will ease away as your body adapts to the hormonal changes. You don’t usually need to see a doctor unless it becomes severe and turns into Hyperemesis gravidarum and its symptoms, including dehydration, electrolyte imbalance, and decreased urination.


During early pregnancy, levels of the hormone progesterone increase significantly and a side effect of this is you can feel sleepy at any time of the day. To counter this, you should aim to rest and relax as much as you can. A specialist and well considered healthy diet and light exercise might help increase your energy, but don’t overdo it.

Increased urination

Pregnancy will increase the frequency – and possibly the amount – that you want to pee. This is caused by the overall amount of blood in your body increasing during pregnancy, which causes your kidneys to process extra fluid, and that just ends up in your bladder. You should also ensure that you drink plenty of water in your pregnancy, so have a bottle of water with you as much as possible. Meanwhile, round the other side, you may experience a good deal of constipation, caused by higher than normal levels of the hormone progesterone, which can slow the movement of food through your digestive system. You can ease this by drinking more water – increasing the need to pee, but also alleviating the constipation – you could also consider fruit juice, and prune juice in particular.

You might also experience tender, swollen breasts as they start to expand, and a good deal of heartburn. Some of the hormones end up relaxing the valve system between your stomach and oesophagus and can allow stomach acid to leak into your oesophagus, causing the heartburn sensation. We promise it’s not all bad though!

On top of those physical conditions, you are likely to experience heightened emotional states as the chemical cocktail of hormones course through your bloodstream. You are likely to experience mood swings, irritability, sadness, and anxiety, mostly driven by hormonal changes but also a product of the subliminal realisation that you are bringing a new life into a world that is full of surprises!


The Science-y Bit!

Once an egg is fertilised and attaches itself in your uterus – essentially the start of your pregnancy – your placenta develops and starts to flood your body hormones that are essential to your baby’s growth. As one of the main hormones, human chorionic gonadotropin (hCG) rises sharply in the first trimester as the new life is kick-started, but finally dips and levels off at around four months into the pregnancy.

The hCG has the main role of keeping the embryo firmly implanted in the uterine lining and promoting its accelerated growth. On the downside, it may make you feel especially tense and prone to mood swings. On top of this, both progesterone and oestrogen help sustain the pregnancy and cause the build-up of the system of blood vessels that help the baby grow.

These will be evident throughout the entire nine months of pregnancy, and on the whole, they don’t upset the system as much as hCG.

How to Handle your First Trimester

One of the best coping strategies is to relax and take things as they come. Realise that you are going to be all over the shop with hCG, oestrogen, and progesterone, and try not to react to what you may see as irritations. You can help this by explaining to those around you that you are pregnant and that you are likely to have mood swings. Hopefully, this means that they will be considerate and help you maintain a mental balance. And also go grab you that tub of Ben & Jerry’s at midnight because you’re craving it!

Secondly, you can help by taking care of yourself and maintaining your health throughout your pregnancy. Take regular low impact exercise, such as walking and follow a good diet to both cope with the negative feelings and intensify the positive ones. Data also shows that eating omega-3 fatty acids may improve mood symptoms in pregnant women, so tuck into the fresh fish.

Both the physical and emotional side effects should pass pretty quickly as your body adjusts to hormones and you become less anxious about the world in general and focus on your new baby.

You will be starting to have ultrasound scans with your midwife, GP or maternity team, to check the growth of your new baby in the first trimester. These scans will be:

  • The Dating and Viability Scan. This is done between the 6th and the 9th week, and is used to confirm pregnancy, and observe the condition of the gestational sac and cardiac activity for normal function.

  • The Abdominal Scan. This scan is carried out around the 10th week, and the ultrasound device probes the lower stomach to get a good view of the growing baby. This is simply a routine scan.

  • The Nuchal Translucency Scan. This is carried out sometime between the 11th and the 13th week and is done to evaluate any congenital anomaly or birth defects if present. This is sometimes referred to as the early morphology scan or NT scan.

  • Transvaginal Scan (TVS). This may be carried out as a back-up scan to the dating scan and is simply used to get a better or cross-reference image of the baby.

Scans are generally routine, and you will be able to keep images of your baby.

It’s only natural that you’ll feel very different as your body adapts for your baby, no don’t panic! Your first trimester is a time to start embracing the fact that you are having a baby, and that can be enormously uplifting. You will have loads of organising to do and the first trimester is a great time to start doing them as you are likely to become more lethargic as your pregnancy progresses and you really won’t feel like decorating the nursery as you enter your third trimester. This is the time that you should be chatting to your Midwife and other mums, to get a greater understanding of the pregnancy ahead of you.

Your first trimester is probably going to be the most profound of the three trimesters since you will notice a huge difference in your body, unlike anything that has happened before, but embrace it with your partner and family and enjoy the coming months.

If you can’t wait to meet you little one and are interested in our scanning services to spend time with your baby, just want a check-up, or are interested in an early pregnancy scan – contact us today or book a complimentary consultation.

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