3 weeks pregnant

How big is your baby at 3 weeks?

Smaller than 0.2 mm across — a ball of cells called a blastocyst. Human blastocysts measured in an Italian IVF laboratory averaged 0.14 mm across at the early stage and 0.19 mm once fully expanded. By week 4 the NHS puts the embryo at about 2 mm, roughly ten times bigger.

It is measured across because it is a sphere, with an outer layer of cells (the trophectoderm) and an inner cell mass.

What is happening at 3 weeks?

This is the week a pregnancy actually begins. In a textbook 28-day cycle an egg was released at about the end of week 2. If sperm met it, it has been fertilised, and over the following days it travels along the fallopian tube, which connects the ovary to the womb, growing into a blastocyst.

Then it has to implant in the lining of the womb. In a US study of 221 women who collected daily urine samples, published in the New England Journal of Medicine, implantation — detected by hCG first appearing in urine — happened 6 to 12 days after ovulation in pregnancies that lasted at least six weeks, and on day 8, 9 or 10 in 84% of them. On the textbook calendar that is mostly the start of week 4, occasionally the end of week 3.

Once it has implanted, the growing placenta begins to make hCG, the hormone tests look for. Healthdirect, Australia's national health information service, says low levels can usually be found in the blood about 6 to 10 days after ovulation.

3 weeks pregnant symptoms: cramping and discharge

You are unlikely to feel anything at 3 weeks. Most pregnancies have not implanted yet, and the NHS week-by-week guide says that to start with you may not have any symptoms at all. Cramping, bloating, sore breasts or extra discharge this week cannot tell you whether you have conceived; PMS or pregnancy symptoms and two week wait symptoms explain why.

Some people notice light spotting as the fertilised egg burrows into the womb lining; the NHS lists it among early symptoms and says to see your doctor if you bleed in pregnancy. Given when implantation usually happens, it is more likely in week 4 than week 3. Implantation bleeding vs a period sets out the differences.

Can a pregnancy test be positive at 3 weeks?

Very unlikely. A test cannot detect a pregnancy before it implants, and most have not implanted by the end of week 3. Healthdirect says home pregnancy tests usually detect hCG about 2 weeks after conception, and that testing too early can give a false negative.

Even the day your period is due — the start of week 5 in a 28-day cycle — is not foolproof. A later analysis of the same US study, published in JAMA, found 10% of pregnancies had not yet implanted on the first day of the missed period, so even a perfect test could detect at most 90% that day, rising to 97% a week later. Healthdirect's advice: if a test is negative on the first day after your missed period, wait a week and retest if you still think you might be pregnant.

Our pregnancy test date calculator gives the earliest sensible day, and faint line on a pregnancy test explains in-between results.

3 weeks pregnant hCG levels

There is no normal hCG level for 3 weeks. Before implantation there is no pregnancy hCG at all, and healthdirect's guide to hCG levels by week does not start until 4 weeks, where its range begins at zero. Healthdirect stresses that the table is a guide only and that every woman's levels are different.

What matters more than one number is how levels change: healthdirect notes that low levels, or levels that rise more slowly than expected, may be due to an ectopic pregnancy or a higher risk of miscarriage.

Can you see 3 weeks pregnant on an ultrasound?

No. A ball of cells under 0.2 mm that has not implanted cannot be seen on a scan, and even after implantation it takes time. In a Canadian fertility-clinic study of 35 women with normal pregnancies scanned through the vagina, the pregnancy sac could not be seen while hCG was below 1,100 IU/L. The yolk sac was never visible before day 36 of pregnancy, and a heartbeat never before day 41 — 5 weeks and 6 days.

Your belly will not change this week either. What each early scan can show, and who is offered one, is covered in early pregnancy scans.

Is 3 weeks pregnant 1 week after conception?

Roughly, yes. The NHS dates pregnancy from the first day of your last period, and the standard calculation ACOG describes assumes ovulation on day 14 of a 28-day cycle. So 3 weeks pregnant is about one week since conception.

If you are counting from the day you conceived — from a known ovulation date, say — add two weeks to get the number your midwife or doctor will use. Three weeks after conception is about 5 weeks pregnant, a different stage with different advice. After IVF, ACOG says the due date comes from the embryo's age and the transfer date instead.

Is 3 weeks pregnant 1 month?

Week 3 is the third week of month 1. Month 1 runs from week 1 to week 4, so you reach one month at the end of next week. There is no official weeks-to-months map, and a calendar month averages about 4.3 weeks, so two apps can disagree about which month you are in.

How common is very early pregnancy loss?

In the same daily-urine study, 25% of the 189 pregnancies detected by hCG ended in early loss, before six weeks after the last period. The risk was higher the later a pregnancy implanted: 13% of those that implanted by day 9 after ovulation ended early, rising to 82% of those implanting after day 11. A loss this early is sometimes called a chemical pregnancy.

Frequently asked questions

Can you get a positive pregnancy test at 3 weeks?

Very unlikely. A test can only detect hCG once the blastocyst has implanted, and in most pregnancies that happens 8 to 10 days after ovulation, around the start of week 4. Healthdirect says home tests usually detect hCG about 2 weeks after conception, so the day your period is due is the earliest sensible time to test.

What does cramping at 3 weeks pregnant mean?

Mild cramping this week cannot tell you whether you have conceived, because most pregnancies have not yet implanted. Severe or one-sided pain is different. If you might be pregnant and have tummy pain low down on one side with bleeding or shoulder-tip pain, the NHS says to contact a GP or NHS 111 straight away.

What does a baby look like at 3 weeks?

Not like a baby. It is a blastocyst: a ball of cells with an outer layer and an inner cell mass, measuring around 0.14 to 0.19 mm across in an IVF laboratory study. It is far too small, and too early, for a scan or photograph to show, so "3 weeks pregnant" pictures online are diagrams.