Your embryo is now the size of a sesame seed — around 4mm — and the pace of development this week is extraordinary. The structure that will define your child's entire existence is being laid down right now: the neural tube.
My midwife told me at my booking appointment that the neural tube closes in week five or six. I'd been taking folic acid religiously but I hadn't really understood why until she explained what it actually does. It felt so important, so urgent. Like I finally understood what I was protecting.
The neural tube is a narrow channel of cells that will close over the coming days and become your baby's brain and spinal cord — the entire central nervous system. It runs from what will be the top of the head to the base of the spine. The closing begins in the middle and zips outward toward each end. If it closes completely and correctly, the result is a healthy brain and spinal cord. This is why folic acid is most critical right now, in these precise weeks — it significantly reduces the risk of neural tube defects like spina bifida. If you haven't been taking it, start immediately.
Alongside the neural tube, the foundations of the heart are taking shape. A simple tube-like structure — not yet a recognisable four-chambered heart — is beginning to beat. It may be visible on a very early ultrasound at week 6 or 7, though not always at week 5. The absence of a visible heartbeat on an early scan at this stage does not mean something is wrong; it simply means the scan may have been too early.
The three germ layers from last week are rapidly differentiating into specific structures. The face, in the most rudimentary sense, is beginning to form — two dark spots that will become eyes, a small depression that will become the mouth, and the earliest hints of ears and nose.
Week 5 is, for most people, when pregnancy stops being a fact and starts being an experience. hCG — the pregnancy hormone that's been quietly doubling every 48–72 hours since implantation — is now at levels where its effects become very difficult to ignore. The most famous effect is nausea. The most underrated is what it does to your sense of smell.
Superhuman sense of smell — one of the most striking and least discussed symptoms of early pregnancy. Smells that were previously neutral or pleasant can become violently nauseating. The biological theory is that heightened smell sensitivity protected early humans from consuming things harmful to pregnancy. In practice it means your morning coffee, your partner's deodorant, or the smell of a specific food may suddenly become unbearable.
Profound fatigue — distinct from ordinary tiredness in quality as well as degree. Your body is directing enormous energy into building the placenta and supporting rapid embryonic growth. Progesterone, which promotes sleep, is also rising sharply. The exhaustion of early pregnancy is physiological, not psychological. Rest is the only treatment.
Increased urination — rising hCG and progesterone increase blood flow to your kidneys, causing them to filter more efficiently. You will notice more frequent trips to the toilet, even though your uterus is not yet large enough to press on your bladder.
Week five was when it hit me. I went from vaguely tired and slightly queasy to horizontal, unable to eat anything that wasn't plain crackers, unable to be near the kitchen when anything was cooking. It felt extreme. My midwife told me that how bad the nausea is doesn't correlate to how the pregnancy is going. That was genuinely useful to hear.
It is worth knowing clearly: nausea severity is not an indicator of pregnancy health. A pregnancy with severe nausea is not healthier than one with mild nausea. An absence of nausea does not indicate a problem. hCG levels vary considerably between individuals, and the brain's sensitivity to them varies further still. What you experience is not a measure of anything except your own individual biology.
There is a particular cruelty to week 5 that is almost never acknowledged in the cheerful pregnancy content you will encounter. This is the week when the physical symptoms ramp up — when you start to feel, genuinely and sometimes severely, unwell — and yet it is also the week when almost nobody knows you are pregnant. You are carrying something enormous and invisible, feeling terrible in ways you cannot explain to most people, and doing all of it in secret.
The contrast between the enormity of the news and the ordinariness of daily life can feel vertiginous. Sitting in a meeting feeling nauseous, declining wine at dinner with an invented excuse, cancelling plans because the exhaustion is real but unexplainable — these small acts of concealment have an emotional weight that compounds over weeks. This is worth naming.
I had a work presentation in week five. I nearly threw up twice during it. Nobody knew. I just sat there presenting slides, thinking: there is a person forming inside me right now and I am pretending everything is completely normal. It was the strangest I have ever felt.
If you are still in a state of shock, unreality, or ambivalence from last week, that is entirely normal and does not need to resolve on any particular schedule. Feelings about early pregnancy do not follow a linear progression toward settled contentment. Some people feel acutely happy. Some feel anxious. Some feel both simultaneously. Some feel little of anything for weeks, and then it arrives all at once.
The secrecy of early pregnancy is one of the most isolating parts of the whole experience. If there is one person — a close friend, a sibling, your GP — that you can be honest with during these weeks, that support tends to be disproportionately valuable. You do not have to wait until 12 weeks to tell anyone.
These guides cover the themes of week 5 in full — each one connects directly to where you are right now.
This is likely the week when the pregnancy stops feeling abstract. Last week was a fact. This week it becomes visible — in the exhaustion, in the nausea, in the way certain smells produce a reaction that is impossible to fake or ignore. Your partner is not exaggerating. What they are experiencing is real, significant, and in many cases genuinely debilitating.
The challenge for partners in week 5 is that the person they love is suffering, and there is very little that can be done to fix it. There is no medication that makes pregnancy nausea disappear (though there are things that help), no action that resolves the exhaustion, no way to speed up the weeks until it eases. What is available is presence, patience, and practical adaptation.
- Take over the cooking. The smell of food cooking is one of the most common nausea triggers. If you are the one preparing meals, ask what — if anything — sounds tolerable. Bland, cold foods tend to be better than hot, aromatic ones.
- Don't be offended by food refusals. If your partner suddenly cannot eat a meal they previously loved, this is not about the meal or about you. The aversion is involuntary and will pass.
- Let them rest without guilt. Falling asleep at 8pm or spending a Sunday horizontal is not laziness. The fatigue of early pregnancy is physiological. The most helpful thing you can do is make rest easy rather than complicated.
- Cover for them socially. If people ask why your partner isn't drinking at a gathering, or why they left early, having a ready excuse ready protects the secret without putting the burden entirely on them to manage it.
- Ask how you can help — and mean it. There may not be much. But being asked, and being believed, matters more than any specific action.
Take folic acid today if you haven't already — and take it every day. The neural tube is closing right now, this week. 400mcg daily of folic acid reduces the risk of neural tube defects by up to 70%. It is available over the counter at any pharmacy for a few pounds, and it is one of the most evidence-backed interventions in the whole of pregnancy care.
If you have already started, keep going until at least week 12. If you are taking a pregnancy multivitamin, check that it contains at least 400mcg folic acid — most do, but it is worth checking. If you have a family history of neural tube defects, or are taking certain medications including some anticonvulsants, speak to your GP — a higher dose (5mg) may be recommended.
Small, frequent meals. Large meals can trigger or worsen nausea. Grazing every 2–3 hours on bland, easy foods (toast, crackers, rice, plain pasta) is more manageable than three full meals.
Cold food over hot. Hot food has stronger aromas, which can trigger nausea. Cold or room-temperature food is often better tolerated.
Ginger. Ginger (tea, biscuits, lozenges, capsules) has modest but real evidence for reducing pregnancy nausea. It is safe in normal food quantities.
Fresh air. Simple but effective — stale or warm air tends to worsen nausea. A cool, well-ventilated space often helps.
If none of this works, ask your GP. There are safe, effective anti-nausea medications that can be prescribed in pregnancy. You do not have to simply endure it.
If your nausea is severe — or if you're finding it difficult to function, eat, or drink — raise this at your booking appointment and don't wait:
Pregnancy nausea is severely undertreated in the UK. Many people do not know that safe, effective anti-nausea medication can be prescribed, or feel reluctant to ask for it. Your midwife can assess whether medication is appropriate and refer you for additional support if needed. You are not wasting their time. Severe nausea is a medical symptom, not a character test.