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Trimester 2 · Week 25 of 40

Week 25 of pregnancy: Baby's Startle Reflex

Pelvic girdle pain, restless nights and a haemoglobin re-check, while your baby adds fat and reacts to sound more often.

Last updated 28 September 2026

What's happening this week?

Your baby is filling out, with more fat under the skin and a nervous system that is maturing quickly. For you, the bump is now heavy enough to strain your pelvic joints, and nights may feel shorter. Two things are worth doing now. If your pelvis hurts when you walk, climb stairs or turn in bed, mention it early, because pelvic girdle pain responds well to physiotherapy. And make sure your haemoglobin check and second glucose test are part of the plan for these weeks.

Baby's development

Around 25 weeks your baby is adding body fat steadily. As it builds up under the skin, the skin becomes less translucent and the body looks a little less thin. There is still a long way to go: most fat is laid down in the third trimester.

The nervous system is maturing rapidly, and responses to sound are becoming more frequent and spread across more pitches than the low tones a minority of babies first reacted to around 19 weeks. From about 24 to 25 weeks, a blink or startle in response to strong sound and vibration can be seen on ultrasound. Consistent responses in almost every baby follow a few weeks later, so you may notice a sudden movement after a loud noise.

The nostrils open around now. Your baby does not breathe air, but continues the breathing-like movements with amniotic fluid that began in the first trimester. The lungs have only just started making small amounts of surfactant, the substance that stops the air sacs collapsing, and it does not become mature until about 34 to 36 weeks.

Your baby's size

About the size of a head of lettuce

34.6 cm

13.6 in · Length

660 g

Weight

Week 25

Gestational age

Since 20 weeks babies are measured from crown to heel, typically around 34 to 35 cm at this point. The 660 g shown is a little below common ultrasound estimates of about 700 to 900 g, and a healthy baby can weigh roughly a quarter more or less than the middle figure. The lettuce is a loose picture only.

Your body this week

Your uterus now reaches well above your navel. At each visit your doctor or midwife may measure from the pubic bone to the top of the bump: from about 24 weeks, that distance in centimetres roughly matches the number of weeks, give or take 2 cm. It is a rough screening check, and a measurement well off the expected range usually leads to a scan.

The weight of the bump and loosening of the ligaments load the joints at the front and back of your pelvis, and for about 1 in 5 pregnant women this becomes pelvic girdle pain. Your blood volume is still expanding too. Plasma is roughly 29 percent above pre-pregnancy levels in weeks 21 to 27 and rises faster than red cells, so haemoglobin normally dips a little. That natural dilution is different from true iron-deficiency anaemia, which affected just over half of pregnant women in India in the NFHS-5 survey.

Sleep can become harder from here, as a bigger bump, night-time toilet trips, heartburn, leg cramps and restless legs all break up the night.

Symptoms you may notice

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

Pelvic girdle pain: Pain over the pubic bone, lower back, buttocks or groin, worse when walking, on stairs, standing on one leg or parting your legs. Sitting down to dress, keeping your knees together when getting out of a car, and taking stairs one at a time may help. Ask about physiotherapy rather than putting up with it.
Restless legs: An uncomfortable urge to move your legs, usually in the evening or in bed, and one of the common reasons for poor sleep in later pregnancy. Mention it if it keeps you awake, and do not start supplements for it without advice.
Backache: The bump shifts your centre of gravity and strains the lower back. Low heels, a supported sitting position and avoiding heavy lifting help. Backache that comes and goes in waves before 37 weeks can be a sign of preterm labour and needs checking.
Tiredness: Tiredness that feels out of proportion, or comes with breathlessness or dizziness, is worth mentioning, because anaemia is common and treatable.

Medical care and tests

Haemoglobin check
Routine
Each antenatal visit in India; around 24–28 weeks elsewhere
In India haemoglobin is checked at every antenatal visit and compared with your first result. Below 11 g/dl counts as anaemia, with 7 to 11 considered moderate and under 7 severe. If you are anaemic you are usually given a treatment dose of iron and rechecked after about a month.
Second glucose test for gestational diabetes
Routine
24–28 weeks
India tests every pregnant woman twice: at the first visit, then again in this window if the first result was normal, at least 4 weeks apart. You drink 75 g of glucose in water, fasting or not, and blood is taken 2 hours later. A high result leads to diet advice, blood sugar monitoring and sometimes medicine.
Mid-pregnancy antenatal visit
Routine
14–26 weeks in India; 25 weeks in the UK for a first baby
Blood pressure, weight, urine and bump size are checked; the UK 25-week appointment also covers movements and mental health.
Physiotherapy for pelvic pain
Only if needed
When pain starts
If pelvic pain limits walking or sleep, a physiotherapist can assess you and teach ways to move with less pain. Ask whether your hospital can refer you.

Test timing differs between hospitals and countries, so follow your own doctor's schedule.

Nutrition this week

Iron deserves a second look now, because your blood volume is still rising and anaemia is very common in India. Build meals around rajma, kala chana, lobia, masoor and leafy greens such as palak, methi, bathua or sarson; if you eat them, eggs, fish and meat also provide iron.
Add a vitamin C food to the same meal to help absorption: lemon over dal, guava or orange after lunch, or amla chutney with roti.
Keep taking the iron-folic acid tablet daily as prescribed, and keep tea and coffee about an hour away from it and from meals.
If the tablet upsets your stomach, tell your doctor or ANM rather than stopping; they can advise on what to try.

Movement and exercise

Keep up gentle, regular activity unless you have been told otherwise. Walking, swimming, stationary cycling and prenatal yoga all count towards the usual target of about 150 minutes a week.
With pelvic girdle pain, shorten your stride, avoid movements that part your legs widely and choose flat walks over stairs for a while. Stop anything that makes the pain sharper.
Avoid long spells lying flat on your back; do floor exercises on your side or propped up on cushions.

Things to keep in mind

Ask family to take over heavy jobs such as lifting water buckets, gas cylinders or wet laundry.
A pillow between your knees at night helps many people with hip and pelvic pain.
If your job keeps you on your feet, ask whether you can sit for part of the day, as prolonged standing is best avoided.
Jot down what is disturbing your sleep, such as cramps, restless legs or heartburn, so you can describe it clearly at your next appointment.

When to contact your doctor

Call your doctor or midwife the same day if you have

Burning or stinging when passing urine, or cloudy or smelly urine.
A fever of 38°C or more.
Pain, swelling or warmth in one calf.
A headache that will not go away, or sudden swelling of the face, hands or feet.
Any light bleeding or spotting.

Get emergency care now if you have

Your baby's movements slow down, change or stop: contact the maternity unit straight away, even at night.
Heavy bleeding, or severe or constant abdominal pain.
Regular tightenings, period-like pain, pelvic pressure or fluid leaking from the vagina before 37 weeks.
Severe headache with blurred vision or flashing lights, or pain under the ribs on the right.
Chest pain, sudden breathlessness or fainting.

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

Is my haemoglobin where you would like it, and do I need a different iron dose?
When should I have my second glucose test?
Could my pain be pelvic girdle pain, and can you refer me to a physiotherapist?
Is my bump measuring as expected for my dates?

Week 25 checklist

Book or confirm the 24–28 week glucose test
Take your iron-folic acid tablet, away from tea
Ask about physiotherapy if your pelvis hurts
Try a pillow between your knees tonight
File your latest haemoglobin result

Frequently asked questions

Is pelvic pain at 25 weeks normal?

Some aching as the joints loosen is common. Pain at the front or back of the pelvis that is worse when walking, on stairs or when parting your legs may be pelvic girdle pain. It does not harm the baby and physiotherapy can ease it, so mention it early. Severe or constant pain, or pain with bleeding or fever, needs checking the same day.

Why is my haemoglobin lower than at my first visit?

In mid-pregnancy the liquid part of your blood expands faster than the red cells, so haemoglobin normally falls a little. In India a result below 11 g/dl is counted as anaemia, and iron deficiency is very common. Your doctor may then raise your iron dose and recheck after about a month.

Can my baby hear me at 25 weeks?

Babies respond to sound more often from now on, and some blink or startle at strong noise and vibration. Reliable responses in nearly all babies come at about 27 to 28 weeks. Talking or singing to your bump is a pleasant habit if you enjoy it, but no special music or programme is needed.

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.