5 weeks pregnant: symptoms and baby development
The heart starts to beat this week.
First trimesterMonth 25 min read
By Solesia, from public clinical guidanceUpdated
The test is positive, and the news is still new enough to feel unreal. You may check it again, or tell one person and no one else for a while. Inside, quietly, the biggest single change of the whole pregnancy is under way: a cluster of cells is folding into a tube, and by the end of the week that tube is a heart, beating. It is far too small to hear, but it is there. For you, the first real symptom tends to be tiredness, a heaviness that arrives in the afternoon and asks you to lie down, the earliest sign of how hard your body is working.
How big is your baby at 5 weeks
About the size of an apple seed
0.1 in long·under 0.1 oz
Baby development at 5 weeks
At 5 weeks your baby measures about 0.1 inches, the size of an apple seed. They have changed shape since last week: the flat disc has folded into a curved tube, with a head end and a tail end, and a groove along the back is closing over to become the spinal cord and brain. This is why folic acid matters right now, before you have seen anyone.
The heart begins as two tubes that fuse into one. Around now that tube starts to twitch, then to contract in a steady rhythm, pushing blood through vessels that are forming at the same time. It is too small and too early to hear or see on a scan; by next week an ultrasound can sometimes catch the flicker.
On the head end, the first hint of a face is appearing: two spots where the eyes will be and a bump that becomes the nose. Their food still comes from the yolk sac, a small balloon beside them, while the placenta keeps growing into your blood supply and gets ready to take over.
Your body at 5 weeks
Tiredness this week is expected, and it can be heavier than anything you are used to. Progesterone has climbed steeply, your body is building the placenta from scratch, and the amount of blood you carry is starting to rise. None of that shows, which makes it hard to explain to other people. Rest when you can and let the day be smaller than usual.
Breasts that ache and feel heavier are expected too, often the first thing people notice. The glands inside are preparing months ahead of time, and the veins across them may show more clearly. Nausea can begin now for some and not for weeks for others, and both are ordinary.
Your mood may swing in ways that surprise you, from delighted to tearful in an hour. Hormones are the reason, and so is the size of what has just changed. Telling one person you trust often helps more than any tip.
Common pregnancy symptoms at 5 weeks
- Tiredness. Progesterone plus the work of building a placenta. Earlier nights and a short lie-down if you can get one.
- Sore, heavy breasts. Glands developing early. A soft bra, and a size up if the old one pinches.
- Mood swings. Hormones on top of big news. Sleep and one person you can say anything to.
- Needing to pee more. More blood to filter and a uterus that is starting to lean on the bladder. Keep drinking anyway.
- Food that suddenly repels you. Smell and taste sharpen fast. Cold, plain food is easier than hot, fragrant food.
- Light cramping. The uterus growing and settling. Warmth, water and rest.
- More discharge. Thin, white and mild. It protects against infection and is expected from now on.
When to call your provider at 5 weeks
Spotting that stays light is common now. Bleeding like a period, or pain on one side, is worth a call the same day.
Two things are worth a same-day call at any point in pregnancy: bleeding that is more than spotting, and pain that is severe or does not ease. From the second trimester, add fluid leaking and any change in your baby’s usual pattern of movement. You do not need to be sure something is wrong to call; that is what the number is for.
What to do at 5 weeks
- Long-term conditions and regular medicines. If you take anything daily, for thyroid, blood pressure, mood, epilepsy or diabetes, call the prescriber this week rather than waiting for the first visit. Many medicines are fine; a few need swapping early.
- The first prenatal visit. If you have not booked it, do it now for 8 to 10 weeks. Some offices see you sooner if you have had a previous loss or a condition that needs watching; say so when you call.
- Folic acid and a prenatal vitamin. The spinal cord is closing this week and next, so 400 mcg of folic acid a day is the one supplement that cannot wait. Prenatal vitamins usually include it, along with vitamin D.
- Caffeine. Up to about 200 mg a day is fine, about one 12-ounce cup of coffee. Tea, cola and energy drinks count toward it.
Common questions at 5 weeks
Can you hear the heartbeat at 5 weeks?
Not yet. The heart has only just begun to beat and it is a fraction of an inch across. A vaginal ultrasound can sometimes show a flicker from around 6 weeks, and a handheld Doppler usually picks up the sound from 10 to 12 weeks. At 5 weeks there is nothing to hear, and that is expected.
Is it normal to have no symptoms at 5 weeks?
Yes. Symptoms depend on how your body responds to hormones, not on how well the pregnancy is going, and plenty of people feel entirely themselves until 6 or 7 weeks. Some never get nausea at all. Symptoms that come and go from day to day are ordinary too.
Why am I so tired at 5 weeks pregnant?
Progesterone, which has risen steeply, has a sedating effect on its own, and on top of it your body is building an organ, the placenta, and increasing its blood supply. The tiredness usually eases in the second trimester. Iron-rich food, water and early nights help; nothing else really does.
Can I exercise at 5 weeks pregnant?
Yes, and it helps with tiredness and mood. Keep doing what you did before, at a level where you can still talk. The aim is about 150 minutes a week of moderate activity, walking counts. Stay cool, drink water and skip anything with a real chance of a fall or a blow to the belly.
Written from public clinical guidance, including NHS: Week 5, ACOG: How your baby grows, ACOG: Changes in your body, NHS: Tiredness and NHS: Discharge. This page is general information, not medical advice, and does not replace your provider.