Ask the Expert: What Is Trimester Zero and Is It Important to Prepare Your Body Before Trying to Conceive?

Here, we talk with Consultant Obstetrician, Gynaecologist, and fertility expert Venkatesh Subramanian about trimester zero, and why small changes can make a big difference both for getting pregnant and supporting your pregnancy.

If you’re familiar with pregnancy terms, you will probably know that the word ‘trimester’ relates to a three-month period in a human pregnancy (essentially 40 weeks being roughly divided into a 1st, 2nd and 3rd trimester). And now, along with the arrival of a relatively new fourth trimester (the three months after a woman gives birth) we have yet another new trimester - “trimester zero”. If you haven’t heard of this, it’s a term that’s becoming increasingly popular among women discussing fertility and pregnancy online, and it refers to the three months before a woman actively starts trying for a baby. 

If you’re preparing to conceive, the idea behind trimester zero is that what you do before you get pregnant could influence your experience of conceiving, your pregnancy, and also your baby’s early development. 

While there’s currently no robust scientific evidence to prove that adopting the ‘ideal’ pre-conception lifestyle will directly determine your child’s long-term health outcomes, I do agree that preparing your body for pregnancy can improve your chances of conceiving, and can help to support a healthy pregnancy. 

Rather than seeing trimester zero as a pressure-filled checklist, I prefer to view it as an opportunity to evaluate the areas of your lifestyle that might need tweaking. Could it be that you want to improve your sleep habits? Or you feel your diet could be altered, to include a more diverse range of vegetables? A window of time to gently improve your physical and emotional health can be good for your mind and body – and, if you’re conceiving with a male partner, he might want to consider ways to optimise his sperm health, too.

If everyone who took this advice was guaranteed to conceive, and have a healthy pregnancy, then I wouldn’t be seeing people struggle with fertility, or have any problems in their pregnancy. And similarly, we know of many people who don’t change anything in their lifestyle, and conceive immediately. With this in mind, it’s important to remember that many things that are happening in your body are out of your control. Therefore when patients have come to me asking how to approach trimester zero I say don’t focus on perfection - rather think of it as a time for awareness and gentle preparation.

What areas of health should I look at before trying to conceive?

When preparing for pregnancy, I would consider focusing on:

1. Nutrition

A balanced diet rich in fruit, vegetables, whole grains, lean proteins and healthy fats (including omega 3) supports hormone production and egg health. Maintaining a healthy weight can also improve ovulation and fertility outcomes. If you need specific help in understanding the foods that really matter in conception and pregnancy, seeing a nutritionist can often help. 

2. Folic acid and vitamin D

The NHS recommends taking 400 micrograms of folic acid daily for at least three months before conception (which could be referred to as trimester zero). Taking folic acid is a really easy way to help reduce the risk of neural tube defects, such as spina bifida, in early pregnancy, often before you even know you’re pregnant. Vitamin D is important, too. You need 10 micrograms of vitamin D each day to keep bones, teeth and muscles healthy. You’ll find that a quality pregnancy multivitamin will contain these essential vitamins, and you can start taking them before trying to conceive. 

3. Alcohol and smoking

Reducing or cutting out alcohol altogether is advisable when trying to conceive. When it comes to smoking, this can affect both egg quality and sperm quality, so stopping is one of the most beneficial steps you can take for fertility and pregnancy health. There is less research on the effects of vaping, but I would advise stopping this as well, as there is some evidence to suggest that it can affect a woman’s fertility

4. Exercise

Regular exercise supports metabolic health, stress reduction and hormonal balance. There’s no need for extreme training programmes though, as this can negatively impact your fertility by causing your cycles to become irregular, or stop altogether. Consistency is much more important, with regular exercise that feels good for you being my recommendation. 

5. Mental wellbeing

Stress alone does not cause infertility, but chronic stress can affect sleep, appetite and hormone regulation. Creating space for rest and emotional support is just as important as diet and supplements. You should always try to prioritise your mental wellbeing, and if you’re feeling overwhelmed or dealing with emotions that are not normal for you, it’s important to reach out to your doctor if you feel you need support.

6. Your partner’s health

If you’re trying to conceive with a male partner, sperm health plays a significant role in whether or not you’ll get pregnant. Sperm quality can be affected by smoking, alcohol intake, BMI, and certain medications; conversely, certain supplements can help to support development of healthy sperm. If you look at trimester zero as a shared journey, you can help to support each other to tweak certain areas of your lifestyle that might improve your chances of conceiving. 

If you’re over 35, have irregular periods, a history of endometriosis, polycystic ovary syndrome (PCOS), previous pelvic infections, or a family history of early menopause, an early fertility assessment may provide valuable insight.

A fertility check might include:

• Hormone blood tests
• An ultrasound scan to assess ovarian reserve
• Thyroid function testing
• Semen analysis for a male partner

For many couples, however, there’s no need to investigate before trying, but you might simply want some reassurance that everything seems OK. If you’re under 35 and healthy, I’d recommend trying for a year before seeking medical advice. If you’re over 35, then I would advise only waiting for six months.

I would advise, also, that all men consider doing a sperm test in conjunction with a specialist consultation to ensure there are no issues. If anything is identified, it can be so helpful to go forward with the right advice and guidance on what to do.

Can trimester zero prep prevent morning sickness and exhaustion in early pregnancy?

This is one of the most common misconceptions around trimester zero prep.

There is currently no strong evidence that getting your body ready in trimester zero will make you immune to morning sickness or tiredness in the first trimester.

Morning sickness is thought to be largely driven by hormonal changes, particularly rising levels of human chorionic gonadotropin (hCG - the pregnancy hormone) and oestrogen in early pregnancy. These hormones are essential for supporting the pregnancy, but they can also trigger nausea and vomiting. Extreme tiredness is similarly linked to hormonal shifts and the huge amount of physiological work your body is doing in the early weeks of pregnancy.

Even if you’ve followed all pre-conception health advice to the letter, you might experience significant morning sickness, and this will not be something you can control. Reassuringly, nausea in early pregnancy is often associated with healthy hormonal activity. Preparing beforehand may help you feel stronger going into pregnancy,  but it cannot eliminate natural biological processes.

What are the basics I should focus on?

If the idea of trimester zero advice feels overwhelming, let’s return to the foundations:

• Take 400 micrograms of folic acid daily
• Eat a balanced, nutrient-rich diet
• Maintain a healthy weight
• Exercise regularly 
• Reduce or avoid alcohol
• Stop smoking
• Review any medications with your GP
• Ensure vaccinations are up to date

These are low-effort, evidence-based steps recommended by the NHS that I would also stand by, and they are not based on any social media trends.

I’ve done everything “right” but haven’t conceived after a year of trying. What’s wrong?

One of the hardest aspects of trying for a baby is accepting that some things are outside of our control.

You can eat well, exercise regularly, take your supplements and avoid alcohol, and still not conceive as quickly as you’d hoped – or at all. That can feel deeply disappointing and frustrating.

There are many possible reasons why pregnancy hasn’t occurred yet, including:

• Reduced ovarian reserve (which naturally declines with age)
• Irregular ovulation
• Blocked fallopian tubes
• Endometriosis
• Thyroid imbalance
• Sperm quality 
• Unexplained infertility

Age is one of the most significant factors affecting egg quantity and quality. Fertility naturally declines from your early 30s and more sharply after 35. But even in younger women, difficulties can arise.

If you’ve been trying for a year (or six months if over 35), seeking advice is not a sign of failure: it’s a proactive step forward. Don’t ever feel that it’s unnecessary for you to seek advice early on, if that’s what you want to do. No one experience of trying for a baby is the same, so do what feels right for you.

Could some extra insight help me to conceive?

A fertility check at our clinic can provide clarity, identify potential barriers, and offer tailored advice specific to you and your partner. Sometimes results are entirely normal, and that alone can be reassuring to hear. In other cases, early intervention around an issue we’ve identified can dramatically improve your chances of conceiving.

Fertility assessments can help you plan your next steps by checking key factors that affect fertility and pregnancy. You’ll get clear results from advanced diagnostics, expert guidance on what they mean, and supportive, reassuring care throughout.

I understand that this can be an emotionally complex journey, and always try to give you evidence-based guidance without judgement or pressure.

What should I do first in trimester zero?

In my mind, trimester zero shouldn’t be a test that you can pass or fail. Rather, I view it as a time for preparation, and pre-conception care is like preparing the soil before planting: it can help you conceive, and give your pregnancy the strongest start. 

Whether you’re just beginning to think about trying for a baby, or you’ve been trying for some time without success, having a conversation about your fertility can empower you with knowledge and options.

If you would like a comprehensive fertility check or pre-conception consultation, we’re here to support you.

Make an appointment at our London clinic 

To find out more about our fertility support and pregnancy care,  telephone us on (020) 7244 4200 or make an appointment  online.