Everything you need to know about your first trimester

Becoming a mother is joyous and exciting. But it can also be overwhelming and daunting. During the first trimester (weeks 1-13 of pregnancy), your body undergoes several changes. Although you may not look pregnant yet, you certainly feel it. However, rest assured, any discomfort is temporary and part of the baby-making process. You are growing a tiny human, after all!
 

Hormonal changes during the first trimester

 
The first trimester is marked by a concoction of elevating hormones, which communicate to all areas of the body that you’re pregnant and provide for your growing baby.
 

Oestrogen

 
As you enter your first trimester, oestrogen starts rising to support the endometrial lining for your baby’s development (1). Oestrogen also helps blood flow, which sustains your growing baby, but can also make your breasts tender and achy.
 

Progesterone

 
There’s also an increase in progesterone to prepare the uterine lining for the egg’s implantation. Aside from this, progesterone serves as a muscle relaxant to prevent the uterus from contracting until your little one is ready to be born (2). One downside of this dramatic spike is mood swings and emotional fluctuations.
 

Hormone chorionic gonadotropin (hCG)

 
Your first trimester is characterised by rapidly elevating levels of hormone chorionic gonadotropin (hCG), which supports the growing embryo and signals the body to stop menstruation (3). HCG levels continue to rise until week 10 in pregnancy. This, in part, is behind the morning sickness and nausea that commonly blights the start of pregnancy.
 

Foetal development in the first trimester

 
There’s a lot going on in your first trimester. This period sees your baby’s internal systems take shape, with their brain, spine, cardiac tissues, genitals, inner ear, liver, eyelids, kidneys, pancreas, and lungs developing. By the end of the first 13 weeks, your baby will be around the size of a grapefruit.
 

Common symptoms

 
While no two pregnancies are the same, you may experience the following symptoms during your first trimester.
 

Morning sickness

 
Thanks to the rise in hCG, many women experience morning sickness in the first trimester. Although pregnancy nausea tends to be worse when you first wake up, sickness can flare up at any time of the day. 
 
Sadly, there’s no magic bullet for morning sickness. However, many women find eating little and often, getting plenty of rest, and incorporating more complex carbohydrates (brown rice, sweet potatoes, and wholegrain bread) can help. You may also want to try fresh ginger teas or crystallised ginger when you feel queasy. Vomiting can dehydrate you, so make sure you drink enough water, too.
 
Always consult your healthcare provider if your morning sickness is severe (hyperemesis gravidarum).
 

Tender breasts

 
Caused by fluctuating hormones and swelling milk glands to feed your baby, sore breasts are another pregnancy giveaway.
 
Wearing a gentle and supportive bra may help. You may also want to try a cold compress, opt for loose-fitting clothes, and take regular warm showers to provide some relief.
 

Trouble sleeping

 
Hormonal changes or feeling anxious about your pregnancy can lead to sleep disturbances at this stage of pregnancy.
 
Soaking in an Epsom salt bath before bed and taking supplemental magnesium – a mineral that plays a role in nervous system and psychological function – can support your sleep. Journaling, practising yoga, or meditating could help you unwind and relax before bed.
 
You can learn more about improving your sleep hygiene here.
 

Other symptoms

 

• Mood swings

• Weight gain or loss

• Extreme fatigue

• Headaches

• Lower back and pelvic pain

• Cravings for certain foods

• Food aversions

• Heartburn

• Constipation

 

What nutrients are important during the first trimester?

 
As soon you find out you’re pregnant, eating a balanced, diverse, and whole food diet with a focus on the following nutrients – should become a top priority.
 

Folate

 
Folate refers to vitamin B9, a water-soluble B vitamin naturally found in food. It helps
form the neural tube, which is part of a baby’s nervous system.
 
 
Although you can find folate in green leafy vegetables, beans, and citrus fruits, health officials recommend that all pregnant women should take 400-microgram folic acid daily until the 12th week of their pregnancy (4).
 
Supplementing with folic acid (the synthetic version of folate) during pregnancy – especially before conception and throughout the first trimester – may reduce the risk of neural tube defects, including spina bifida (5).
 
By week 12 of pregnancy, a baby’s neural tubes have sealed, so, in theory, there’s no need to continue taking folic acid. But if your pregnancy multivitamin contains this vitamin, it’s perfectly safe to take it for the rest of your pregnancy.
 
We recommend choosing a prenatal multivitamin that provides folic acid in the most bioavailable form of L-methylfolate, which the body can readily use. 
 

Iron

 
Iron becomes increasingly important in your first trimester. You now need 27mg daily. This mineral contributes to the transportation of healthy red blood cells, which carry oxygen around your body to your tissues, organs, and, perhaps most crucially, your baby (6).
 
Besides increasing dietary iron (red meat, fish, chicken, eggs, beans, nuts, seeds, and dried fruit), many women supplement with iron to support their baby’s growth and development, as well as their energy levels.
 

Iodine

 
Iodine is another critical mineral for your first trimester. Iodine supports the production of maternal and foetal thyroid hormones, which help the development of a baby’s brain and nervous system (7).
 
You can find iodine in fish, dairy, eggs, and some grains. However, it can be hard to meet the increased need for iodine in pregnancy from food alone, especially for those following strict plant-based diets.
 
Supplementing with 150µg of iodine will make a valuable contribution to your recommended daily allowance during pregnancy.
 

Consider taking a prenatal multivitamin

 
Eating a healthy, balanced diet during pregnancy is always a priority. But, sometimes, you run into gaps. A high-quality prenatal multivitamin is an easy and convenient way to ensure your growing baby gets everything they need during the first trimester and beyond.
 
We recommend taking a high-strength fish oil or vegan equivalent derived from plant-based microalgae alongside your prenatal multi. Increasing your intake of the essential fatty acid, DHA (docosahexaenoic acid), supports the visual and cognitive development of your growing baby during the first trimester.
 

Top tips for the first trimester

 

• Eat little and often if morning sickness is affecting you.

• Try to do some gentle movement. Walking and yoga are great.

• Start your pelvic floor exercises.

• Quit smoking and cut out alcohol.

• Cut down on caffeine.

• Get as much rest as you can.

• Start taking a pregnancy multi.

 

Find out more

 
If you found this article on the first trimester useful, you can read our second trimester guide here. Alternatively, please get in touch with our team of expert Nutrition Advisors, who are on hand to provide free, confidential advice.
 

References:

1. (1) Pregnancy hormones: progesterone, oestrogen and the mood swings. NCT (National Childbirth Trust). Available online: https://www.nct.org.uk/pregnancy/how-you-might-be-feeling/pregnancy-hormones-progesterone-oestrogen-and-mood-swings

2. Pascual ZN, Langaker MD, Physiology, Pregnancy. StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559304/

3. Betz D, Fane K, Human Chorionic Gonadotropin. StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532950/

4. (4) Vitamins, minerals and supplements in pregnancy. Available online: https://www.nhs.uk/pregnancy/keeping-well/vitamins-supplements-and-nutrition/

5. (5) Folic Acid Supplementation to Prevent Neural Tube Defects: US Preventive Services Task Force Reaffirmation Recommendation Statement. JAMA. 330(5):454–459. 2023

6. (6) Nutrition During Pregnancy. Available online: https://www.acog.org/womens-health/faqs/nutrition-during-pregnancy

7. De-Regil LM, Harding KB, Peña-Rosas JP, Webster AC, Iodine supplementation for women during the preconception, pregnancy and postpartum period. Protocol. Cochrane Database of Systematic Reviews. Issue 6. Art. No.: CD011761. 2015

 

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