5 weeks pregnant

How big is your baby at 5 weeks?

About the size of a sesame seed — around 2 mm (0.08 in) long, according to the NHS.

You may notice the NHS gives roughly 2 mm for both week 4 and week 5. That is not worth worrying about. Measurements this early are approximate, embryos vary, and being a few days out on your dates makes a far bigger proportional difference now than it will at 30 weeks.

A note on the numbers: in the first trimester babies are measured crown to rump — head to bottom, not head to heel, because the legs are curled. Weight is not reliably estimated this early, so any site quoting grams or ounces before about 14 weeks is guessing.

What's developing this week

This is the week the heart starts. The NHS describes the tiny heart beginning to form and beating for the first time around now — at this stage a simple tube that folds and starts pulsing, not a four-chambered heart. Nothing is audible yet and nothing would show on a scan.

The nervous system develops in parallel: the brain and spinal cord take shape as the neural tube closes. The face is beginning, with a tiny nose and small eyes that stay closed until around 28 weeks. Blood vessels and the umbilical cord are forming, and the placenta is being built.

What you might feel

Week 5 is when most people find out. A period is late, a test is positive, and the ground moves. The NHS lists as common now: extreme tiredness, a metallic taste, sore breasts, nausea at any time of day, mood swings, new food likes and dislikes, a heightened sense of smell, needing to pee more often, milky white discharge, light spotting, and cramping like period pain.

Two things worth naming. Cramping that feels like a period is extremely common at 5 weeks and is usually the womb changing, not a warning — but pain that is one-sided or severe, or comes with bleeding, needs a call. And the NHS notes around 1 in 5 pregnant people feel anxious or stressed during pregnancy. If finding out has left you frightened rather than delighted, you are in ordinary company, and it is worth telling your midwife.

Is 5 weeks pregnant 1 month or 2 months?

Week 5 is the first week of month 2. You have completed one month and are working through the second.

There is no official weeks-to-months map. A calendar month averages about 4.3 weeks, not 4, so 40 weeks is a little over nine months — and two apps can disagree about which month you are in. The most widely used mapping:

• Month 1 — weeks 1 to 4
• Month 2 — weeks 5 to 8
• Month 3 — weeks 9 to 13
• Month 4 — weeks 14 to 17
• Month 5 — weeks 18 to 22
• Month 6 — weeks 23 to 27
• Month 7 — weeks 28 to 31
• Month 8 — weeks 32 to 35
• Month 9 — weeks 36 to 40

Your maternity team will not use months. Everything is booked by week and day — "11 weeks and 3 days" — because a few days change what is offered.

Miscarriage risk at 5 weeks

You are still before the first evidenced milestone. Tommy's estimates early miscarriage — loss before 12 weeks — at 10 to 20 in every 100 pregnancies, with most miscarriages happening in that window. The RCOG describes first-trimester miscarriage as common, around one in five.

You will find week-by-week miscarriage percentage tables all over the internet. Tommy's, which funds the UK's national miscarriage research centre, says openly that beyond the well-evidenced drop after 12 weeks, reliable week-by-week risk research does not really exist. We give you what is evidenced instead.

The milestone you are approaching is real: Tommy's cites research showing that once a pregnancy passes 6 to 7 weeks and has a heartbeat, miscarriage risk drops to around 10 per cent. You are within a fortnight of that point.

The most common cause of early miscarriage is a chromosomal problem that happens by chance. Not lifting something, not a glass of wine before you knew, not stress or exercise. Tommy's states it directly: miscarriages very rarely happen because of something you did or did not do.

Light spotting at 5 weeks is common and often turns out to be nothing. It still deserves a phone call, because being checked is the only way to tell the difference.

Is it safe to fly at 5 weeks pregnant?

Yes, in a straightforward pregnancy. The RCOG is unambiguous: occasional air travel is not harmful in an uncomplicated pregnancy. There is no evidence that cabin pressure or humidity harm you or the baby, and no evidence that flying causes miscarriage, early labour or your waters to break.

Two specifics at 5 weeks. The RCOG notes that pregnancy sickness combined with motion sickness on a flight can make nausea considerably worse — and week 5 is often when sickness begins. And most obstetric emergencies happen in the first and third trimesters, so the practical question is not whether flying is dangerous but whether you would have access to care where you are going.

The risk that is real: blood clots

Pregnancy raises deep vein thrombosis (DVT) risk from the earliest weeks. ACOG puts it plainly: any travel of four hours or more — car, train, bus or plane — doubles DVT risk, and pregnancy adds to that. Under four hours the RCOG says you are unlikely to need special measures. Over four hours:

• Loose clothing, comfortable shoes, an aisle seat, regular walks about the cabin
• In-seat exercises roughly every 30 minutes
• Water steadily; cut down on caffeine
• Graduated compression stockings — not ordinary flight socks, and sized for you by a midwife or doctor

With other clot risk factors you may be advised to have heparin injections around the flight.

Practical points

• No airline restricts travel this early — cut-offs sit around 36 to 37 weeks for one baby, 32 for twins.
• Check what maternity and emergency care exists at your destination.
• Tell your insurer you are pregnant; cover should include pregnancy-related care.
• Some travel vaccines and anti-malarial tablets are unsuitable in pregnancy; travel to Zika areas is not recommended.

The NHS notes many people prefer not to travel in the first 12 weeks simply because of nausea and tiredness, and suggests mid-pregnancy. ACOG names 14 to 28 weeks. Neither calls early travel unsafe.

When to call your midwife or doctor

Early pregnancy is full of sensations that turn out to be nothing. These are the ones worth a phone call.

Get emergency help now

Call your local emergency number (999 in the UK and Ireland, 911 in the US and Canada, 000 in Australia, 111 in New Zealand) or go to an emergency department if you have bleeding with any of the following, which the NHS lists as needing immediate assessment:

• Severe abdominal pain you cannot concentrate through
• Pain in the tip of your shoulder
• Feeling sick, faint or dizzy, or losing consciousness
• Heavy bleeding that soaks through a pad quickly

Sudden sharp abdominal pain with dizziness, faintness or looking very pale can indicate a ruptured ectopic pregnancy, needing same-day surgery. Around 1 in every 90 UK pregnancies is ectopic, and the NHS notes symptoms usually appear between weeks 4 and 12 — where you are now.

Call your midwife, early pregnancy unit or health line today

• Light bleeding or spotting, with mild or no pain
• One-sided pain low in your abdomen or pelvis
• Brown, watery discharge that is new for you
• Pain when you pee or open your bowels
• You cannot keep food or fluid down for 24 hours, your urine is very dark or absent for 8 hours, you feel severely weak or faint, or you are vomiting blood or losing weight — the NHS triggers for pregnancy-sickness help, which is treatable

You do not need a booking appointment first, and you do not need to be certain something is wrong.