15 weeks pregnant

How big is your baby at 15 weeks?

About the size of a apple — around 10.1 cm (4 in) long head to bottom, according to the NHS, weighing roughly 114 g (4 oz).

Your baby has gained roughly a quarter of their body weight in seven days — which is why the produce comparisons now move so fast.

A note on the numbers: up to week 19 the NHS measures crown to rump — head to bottom, because the legs are curled. At week 20 it switches to head to heel, which is why the length appears to leap 10 cm in a week. Weights here are the median from the WHO fetal growth charts, which begin at 14 weeks; half of babies weigh more, half less.

What's developing this week

The NHS sums the week up in terms of logistics: your baby is growing quickly and comes with a lot of packaging — the amniotic sac and fluid — plus their own food supply in the placenta.

ACOG's description of weeks 13 to 16 has the detail. The bones are hardening, especially the long bones of the arms and legs. The skin is still thin and see-through but is about to thicken. Toenails form. The neck is defined and the lower limbs properly developed. Hearing starts to develop. And the lungs begin forming the tissue that will one day exchange oxygen and carbon dioxide, though they will not be capable of it for months.

Movement is constant and completely unfelt. The womb is still small enough, and the baby light enough, that kicks do not reach the abdominal wall with any force.

What you might feel

Round ligament pain

The odd jabbing pain at the sides of your bump. The NHS says putting your feet up and resting helps. It is sharp, brief and triggered by sudden movement. Pain that is constant or severe, or comes with bleeding or a temperature, is not this and needs a call.

Itchy skin

Common, and usually just hormones and stretching skin: unperfumed moisturiser, loose cotton clothing, a cool bath. But the NHS adds a caveat that matters — if the itching gets worse, especially at night, talk to your doctor or midwife. Intense itching, particularly at night or on the palms and soles and often with no rash, can be intrahepatic cholestasis of pregnancy, a liver condition that needs treatment. That is a phone call, not a wait-and-see.

More discharge than you expected

There is more blood flowing around your pelvic area, which makes your body produce more of a milky fluid called leucorrhoea that keeps the vagina clean. The NHS says get it checked if it changes colour (it should be clear, white or creamy), smells strongly, changes texture, or brings itching, soreness or pain when you pee. Thrush is the likeliest explanation, and it is treatable — but not with something off a shelf.

Is 15 weeks pregnant 3 months or 4 months?

Week 15 is in month 4, its second week.

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 — "19 weeks and 3 days" — because a few days change what is offered. The anomaly scan window is 18+0 to 20+6 weeks, not "about five months".

What's happening at your appointments around now

In the UK your next routine contact is the 16-week appointment, so this is the week before. Write down anything you want to raise, because these appointments are short and the list evaporates the moment you sit down.

At 16 weeks the midwife discusses the results of the screening tests taken at booking, gives you information about the next scan, checks your blood pressure and tests your urine. NICE plans 10 routine appointments for a first baby and 7 if you have given birth before, with blood pressure and a urine dipstick for protein at every face-to-face one.

Check now whether your anomaly scan is booked. NICE says it should take place between 18 weeks and 0 days and 20 weeks and 6 days; in the US, ACOG describes the equivalent standard ultrasound as usually done at 18 to 22 weeks. If no date has been mentioned, ask this week rather than next.

Is it safe to fly at 15 weeks pregnant?

Yes, in a straightforward pregnancy — and you are inside the window everyone recommends. 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 none that flying causes miscarriage, early labour or your waters to break. ACOG names 14 to 28 weeks as the best time to travel; the NHS names mid-pregnancy.

At 15 weeks the questions are comfort and paperwork rather than safety: nothing restricts you and the bump is not yet in the way.

The risk that is real: blood clots

Pregnancy raises deep vein thrombosis (DVT) risk, and that does not ease in the second trimester. ACOG puts it plainly: any travel of four hours or more 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

• Airline cut-offs are usually 37 weeks for one baby, 32 for twins, so nothing restricts you yet — but from 28 weeks most airlines want a letter from your midwife or doctor, which the NHS warns can cost money and take weeks.
• Do not book over the anomaly scan window. The NHS offers it between 18 and 21 weeks and, at a push, up to 23 — but the window is not infinitely elastic.
• Check what maternity and emergency care exists at your destination, and tell your insurer you are pregnant so that cover includes pregnancy-related care.
• Some travel vaccines and anti-malarial tablets are unsuitable in pregnancy; travel to Zika areas is not recommended.

When to call your midwife or doctor

The second trimester is the quietest stretch of pregnancy for most people, which is exactly why it is worth knowing what is not ordinary. Maternity units are staffed around the clock.

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:

• Heavy vaginal bleeding, or any bleeding with severe abdominal pain
• Abdominal pain you cannot concentrate through
• Fainting or collapse, chest pain, or sudden breathlessness
• A severe headache painkillers do not touch, blurred vision or flashing lights, pain below your ribs, or sudden swelling of your face, hands or feet — the NHS lists these as pre-eclampsia symptoms, most likely from 20 weeks, needing immediate assessment

Call your midwife or maternity unit today, whatever the hour

• Any vaginal bleeding, however light
• A gush or a steady trickle of fluid from your vagina
• Regular tightenings, or persistent low backache and pelvic pressure
• Discharge that changes colour or texture, smells strongly, or brings itching or soreness
• Itching without a rash, especially at night or on your palms and soles — the NHS asks for this to be checked, because it can be intrahepatic cholestasis of pregnancy
• A temperature, feeling generally unwell, or burning when you pee
• Not feeling movement yet is not on this list. At 15 weeks almost nobody has.

You do not need to be certain something is wrong. That is what the number is for.