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Trimester 1 · Week 5 of 40

Week 5 of pregnancy: Tiny Heart Forming

The heart tube and neural tube form now. Learn the warning signs of an ectopic pregnancy and how much chai or coffee keeps you under the caffeine limit.

Last updated 28 September 2026

What's happening this week?

The embryo is only about 1 to 2 mm long, but a great deal is happening. The layers that will build every organ appear, the neural tube starts to form, and a simple heart tube begins to beat. For you, early signs such as sore breasts and tiredness may be building. Two things are worth doing now: learn the warning signs of an ectopic pregnancy, and take stock of how much tea, coffee and cola you drink, since caffeine should stay under 200 mg a day.

Baby's development

Week 5 marks the start of the embryonic period, which lasts until about 10 weeks. Early this week the flat disc of cells goes through a process called gastrulation and reorganises into three layers. Every organ and tissue in the body will develop from these three layers.

Along the back of the embryo, a strip of cells called the neural plate folds up to form a tube. This neural tube will become the brain and spinal cord. Its two ends close over the following days, into early week 6, which is exactly the window that folic acid taken before and in early pregnancy is meant to protect.

At the same time a primitive heart tube forms. At around 22 days after fertilisation, which is roughly the end of week 5, it begins to contract. It is a single tube rather than a four-chambered heart, and it will loop and divide over the coming weeks. The early gut tube starts to form too.

On a transvaginal scan, a small pregnancy sac is often visible from about four and a half to five weeks, and a yolk sac from around five to five and a half weeks. Flickering cardiac activity is usually not seen until about 6 weeks, so a scan this early that shows only a sac is common.

Your baby's size

About the size of a sesame seed

1-2 mm

0.4 in · Length

< 1 g

Weight

Week 5

Gestational age

The 1–2 mm figure is a typical length for an embryo at this stage, drawn from embryology references rather than a scan. Even a transvaginal scan may show only a sac and yolk sac now, so your own embryo may not be measurable yet. The sesame seed is a rough sense of scale, nothing more.

Your body this week

hCG is climbing quickly, roughly doubling every two to three days, and progesterone is high. Together they keep the womb lining in place and are behind tender breasts, tiredness, bloating and needing to pass urine more often. Nausea usually starts somewhere between 4 and 7 weeks, so it may begin this week or not for a little while yet.

Your womb has begun to grow, but nothing shows from the outside. Some people notice mild, period-like twinges low in the tummy without any bleeding, and a light white vaginal discharge is normal. Pain that is one-sided, severe or getting worse is different and needs urgent assessment.

Many people feel both excited and anxious at this stage, especially because a scan cannot yet show much. If you have had a miscarriage or an ectopic pregnancy before, tell your doctor early, so they can plan care and any early scan in a way that feels right for you.

Symptoms you may notice

Every pregnancy is different - you may have some, all or none of these.

Breast tenderness: Breasts may feel full, tingly or sore, and the skin around the nipples can darken. A soft, supportive bra, including at night, can make this more comfortable.
Tiredness: High progesterone is a common cause. Rest when you can and keep meals regular. Tiredness with dizziness or fainting needs checking.
Early nausea: It may start now or in the next couple of weeks, at any time of day. Keeping a plain snack within reach helps many people.
Passing urine more often: Linked to hCG and extra blood flow to your kidneys. Pain or burning when passing urine is not normal and should be checked the same day.
Mild twinges: Light, period-like aches without bleeding are commonly described. One-sided pain, pain that keeps getting worse, or pain with dizziness needs urgent care.

Medical care and tests

Scan to check where the pregnancy is
Only if needed
Sooner if you have pain or bleeding
An ectopic pregnancy is one that implants outside the womb, most often in a fallopian tube. A home test is positive either way, so it cannot tell you where the pregnancy is. A transvaginal scan can confirm the location, and your doctor may arrange one early if you have pain or bleeding.
Booking your first antenatal visit
Routine
Any time now; within 12 weeks in India
Arrange it now if you have not. Indian guidance asks for the first visit within 12 weeks and ideally as soon as pregnancy is suspected. UK guidance aims for booking by 10 weeks, and US guidance suggests a first assessment before 10 weeks. The visit covers your health history, blood pressure and a set of blood and urine tests.
Folic acid
Routine
Daily, to the end of week 12
Keep going. The neural tube is closing now and over the next few days, so this is precisely the period the tablet is meant to cover.

Most pregnancies do not need a scan at 5 weeks. A scan is arranged sooner when there is pain, bleeding or another reason to check where the pregnancy is; your doctor will decide what is right for you.

Nutrition this week

Keep caffeine under 200 mg a day, the limit used by the NHS and ACOG. Higher intakes are linked with low birth weight and miscarriage.
ICMR-NIN estimates a 150 ml cup of tea at about 30–65 mg of caffeine and brewed coffee at about 80–120 mg. In practice, about two small cups of chai, or one filter coffee plus one chai, keeps most people under the limit. A strong decoction, repeated cutting chai and cola all add up.
Instant coffee, cola, energy drinks and chocolate count too, so include them in your daily total.
Drink tea and coffee between meals rather than with them, as ICMR-NIN advises.
Replace some cups with nimbu pani, buttermilk, coconut water or plain water to help you reach more than 2 litres of fluids a day.

Movement and exercise

You can keep exercising at a moderate level. If you can hold a conversation while moving, the intensity is usually about right.
Brisk walking, swimming and prenatal yoga suit most people at this stage. Avoid hot yoga and exercising in the midday heat.
Stop and seek advice for bleeding, dizziness, faintness or pain during or after exercise. One-sided pain in particular should be checked urgently rather than walked off, even if it eases when you rest.

Things to keep in mind

Share the ectopic warning signs with your partner or a family member, so someone else knows when to call for help.
Shoulder-tip pain, felt where the shoulder meets the arm, can seem unrelated to pregnancy. With tummy pain early in pregnancy it can signal a ruptured ectopic pregnancy and needs emergency care.
Count your caffeine for a day or two to see where you stand.
Avoid saunas, steam rooms and hot tubs, especially in the first 12 weeks.
Tell any doctor, dentist or pharmacist that you are pregnant before treatment or new medicines.

When to contact your doctor

Call your doctor or midwife the same day if you have

Light bleeding or spotting, even without pain.
Cramping that is stronger than a period or does not settle.
Burning or stinging when you pass urine, or cloudy urine.
A temperature of 38°C or higher.
Vomiting so much that fluids will not stay down.

Get emergency care now if you have

One-sided lower tummy pain with dizziness, fainting, shoulder-tip pain, or feeling pale and very unwell.
Heavy bleeding, soaking a pad in an hour or less, or passing clots.
Severe or constant tummy pain.
Fainting or collapse.

In India, call 108 for an ambulance, 102 for free transport for pregnant women in many states, or 112 for any emergency - or go straight to your nearest hospital with a maternity unit.

If something feels wrong, trust that feeling and call - you never need to wait for your next appointment.

Questions to ask your doctor

When is my first scan, and will it check where the pregnancy is?
What should I do if I get pain or bleeding before then?
How much tea or coffee is reasonable for me?
Is my folic acid dose right for my situation?

Week 5 checklist

Save the ectopic warning signs where you can find them
Tally one day's caffeine from chai, coffee and cola
Book or confirm your first antenatal visit
Keep taking folic acid
Tell your pharmacist you are pregnant

Frequently asked questions

What are the warning signs of an ectopic pregnancy?

Warning signs include one-sided pain low in the tummy, vaginal bleeding and pain in the tip of the shoulder. Dizziness, fainting, or feeling pale and very unwell alongside any of these can mean an ectopic pregnancy has ruptured, which is an emergency. A home test is positive in an ectopic pregnancy too, so it cannot rule one out. Get medical help urgently if you notice these signs.

Can I drink chai while pregnant?

Yes, in moderation. The aim is to keep total caffeine under 200 mg a day. ICMR-NIN estimates a 150 ml cup of tea at about 30 to 65 mg, so about two small cups of chai a day keeps most people within the limit, leaving little room for coffee or cola. Stronger brews and bigger cups contain more, so count those as extra.

Is it normal to see nothing much on a scan at 5 weeks?

Yes, it can be. At 5 weeks a transvaginal scan may show only a small sac, or a sac with a yolk sac, and flickering cardiac activity is usually seen from about 6 weeks. If your dates are uncertain, you may be earlier than you think. Your doctor may suggest a repeat scan after a short interval to check progress.

This page is general information, not a diagnosis or a substitute for care from your own doctor or midwife. Pregnancies differ, and timings here are typical ranges rather than deadlines. Read our medical disclaimer and editorial policy.