PREGNANCY GUIDE · PART 2 OF 3

Second Trimester Guide: Weeks 13 to 28

The anomaly scan, the first movements, the glucose test, and how much weight is actually right for you.

Reviewed by Dr. Grishma Ranjangaonkar, MBBS, DGO, ICOG Fellowship in Gynecological Endoscopy · Eva WomanCare Clinic, Vashi

For most women this is the stretch where pregnancy becomes enjoyable. Nausea lifts, energy returns and the bump arrives. It is also when the two most significant tests of the whole pregnancy happen, and when the practical preparation is easiest to do.

Where the second trimester sits in the forty weeksWeeks 13 to 28. The longest of the three, and for most women comfortably the easiest.

What changes, and why this stretch feels different

The placenta takes over hormone production from the ovaries at around week 12, and that single handover explains most of what improves. hCG, the hormone most closely linked to nausea, falls away. Energy returns. Appetite comes back. For many women the second trimester is the only stretch of pregnancy where they feel straightforwardly well, which is exactly why it is the right window for travel, for dental work you have been putting off, and for the practical preparation that becomes hard later.

The work happening inside shifts too. The first trimester built structures. The second grows them and switches them on. Hearing, swallowing, breathing movements, sleep and wake cycles and the beginnings of fat storage all arrive in these sixteen weeks.

How fast the baby actually grows from hereAt 14 weeks the median is under 100 grams. By 28 weeks it is over a kilogram. The shaded band covers the tenth to ninetieth centile, so nine in ten healthy babies sit inside it.

Week by week, weeks 13 to 28

Weeks 13 and 14 — the turn

Around 8 to 9 cm. Fingerprints are forming. The fetus can suck its thumb and makes facial expressions, though not in response to anything. Vocal cords develop. Your uterus rises out of the pelvis, which is why the constant need to pass urine often eases around now.

You may notice: nausea lifting, energy returning, and appetite arriving suddenly.

Weeks 15 and 16 — hearing begins

Around 11 to 12 cm and roughly 100 grams. The bones of the inner ear are in place, so the fetus starts to register sound, mostly your heartbeat, your digestion and the muffled version of your voice. Legs are now longer than arms. Some women feel the first flutters this fortnight, particularly in a second pregnancy.

You may notice: a small but definite bump, and nasal congestion caused by increased blood flow to the mucous membranes.

Weeks 17 and 18 — fat and reflexes

Around 13 to 14 cm. The fetus begins laying down brown fat, which will regulate body temperature after birth. Myelin starts coating the nerves. Yawning, stretching and hiccuping appear. The anomaly scan window opens at 18 weeks.

You may notice: round ligament pain, which is a sharp catch low on one side when you stand or turn too quickly. It is stretching, not damage.

Weeks 19 and 20 — halfway, and the big scan

Around 15 to 25 cm depending on whether length is measured to the rump or the heel, and roughly 300 grams. Vernix, a waxy coating, covers the skin. The anomaly scan usually happens now. Most first-time mothers feel definite movement somewhere in this fortnight.

You may notice: the bump is unmistakable, and the movements finally feel like a baby rather than digestion.

Weeks 21 and 22 — a pattern emerges

Around 500 grams. Sleep and wake cycles establish, and they will not match yours. Taste buds form. Eyebrows and eyelids are complete. The fetus responds to loud noise from outside with a startle.

You may notice: movements settling into recognisable times of day, usually when you finally sit down.

Weeks 23 and 24 — the viability line

Around 600 grams. The lungs begin making surfactant, the substance that lets air sacs stay open. Around 24 weeks is the point from which survival outside the uterus becomes possible with intensive care, which is why this week is a milestone in obstetric terms. The glucose tolerance test window opens.

You may notice: heartburn, as the growing uterus presses upward on the stomach.

Weeks 25 and 26 — eyes open

Around 800 to 900 grams. The eyes open for the first time. Lung development continues rapidly. The fetus responds to your voice with a change in heart rate, which is the first evidence of recognition rather than reflex.

You may notice: back pain as your centre of gravity shifts, and swelling in the feet by evening.

Weeks 27 and 28 — into the third trimester

Around 1 kilogram. Brain tissue develops fast and the smooth surface begins to fold. Regular breathing movements practise the muscles. Eyelashes are present. From 28 weeks you are in the third trimester and appointments become more frequent.

You may notice: breathlessness, leg cramps at night, and Braxton Hicks tightenings that come and go without pattern.

The anomaly scan, in detail

Usually done between 18 and 22 weeks, this is the most thorough look anyone will take at your baby before birth. It takes 30 to 45 minutes and it is a systematic examination, not a photo session, which is why the sonographer goes quiet and why the room can feel tense even when everything is fine.

The brain and skull, including the shape and the fluid spaces inside.
The face, in particular the upper lip, looking for a cleft.
The spine, in long section and in cross section along its whole length.
The heart: four chambers, the outflow vessels and the rhythm. This is the longest part.
The abdominal wall, stomach, kidneys and bladder.
The arms, legs, hands and feet, and the count of long bones.
The placenta and its position relative to the cervix, the cord vessels, and the volume of amniotic fluid.
Growth measurements: head circumference, abdominal circumference and femur length.

What it can and cannot do A good anomaly scan detects most major structural problems, but not all of them, and it says nothing about intelligence, autism or most genetic conditions. Some things are simply not visible at 20 weeks and appear later. A normal scan is genuine reassurance about structure. It is not a guarantee of a perfectly healthy baby, and anyone who tells you otherwise is overselling it.

The one question you cannot ask By law under the PCPNDT Act, 1994, nobody in India may tell you the sex of your baby. The sonographer will not, the report will not say, and the room may have a notice on the wall. This is not obstruction, it is a criminal statute, and it applies to every registered centre in the country.

Feeling the baby move

First-time mothers usually feel definite movement between 18 and 22 weeks. If you have been pregnant before you may recognise it as early as 16. An anterior placenta, meaning one lying on the front wall of the uterus, cushions the movements and can delay it by two or three weeks, which is a normal variation and not a problem.

Early movements feel like bubbles, a muscle twitch or wind. They come and go for several weeks before becoming consistent. What matters in the second trimester is that movements are appearing and gradually increasing, not that they follow any pattern. Formal kick counting belongs to the third trimester, once a pattern has established.

The glucose test and gestational diabetes

Gestational diabetes is common in India, more common than in most Western populations, and South Asian ethnicity is itself a risk factor independent of weight. It usually produces no symptoms at all, which is the entire reason it is screened for rather than waited for.

The test is done between 24 and 28 weeks, or earlier and repeated if you have risk factors. You drink a measured glucose solution and blood is taken at set intervals. It is unpleasant rather than difficult. Follow the fasting instructions exactly, because a test done wrong has to be repeated.

Raises your risk	Why
South Asian ethnicity	Insulin resistance appears at a lower body weight than in European populations
BMI above the Indian cut-off of 23	Excess adipose tissue increases insulin resistance
A family history of type 2 diabetes	Shared genetic susceptibility
PCOS	Insulin resistance is part of the condition itself
A previous large baby, over about 3.5 kg	Often a sign of undiagnosed glucose problems last time
Gestational diabetes in a previous pregnancy	It recurs in a substantial proportion of pregnancies
Age over 30	Glucose tolerance declines gradually with age

If it is picked up, the great majority of cases are managed with diet and monitoring alone, and a minority need medication. Managed well, outcomes are close to normal. Left undetected it raises the risk of a very large baby, birth complications and later type 2 diabetes for you. Our BMI calculator uses the Indian cut-offs, which are the ones that apply here.

Weight gain: how much is actually right

Most weight gain happens in the second and third trimesters, and the right total depends almost entirely on where you started. The ranges below are the international ones, based on the WHO BMI categories. There is a genuine complication for Indian women: the Asian-Indian cut-offs classify overweight from a BMI of 23 rather than 25, so a woman sitting at 24 is in the normal band by the table below and in the overweight band by Indian criteria. In practice most doctors here aim at the lower end of the relevant range. Yours will set a target for you.

Starting BMI	Category	Total gain over the pregnancy	Roughly per week in trimesters 2 and 3
Below 18.5	Underweight	12.5 to 18 kg	About 0.5 kg
18.5 to 24.9	Normal by WHO cut-offs	11.5 to 16 kg	About 0.4 kg
25 to 29.9	Overweight	7 to 11.5 kg	About 0.3 kg
30 and above	Obese	5 to 9 kg	About 0.2 kg

Where the weight actually goes At term, the baby is usually 3 to 3.5 kg of it. The rest is placenta, amniotic fluid, a larger uterus, larger breasts, a blood volume up by almost half, extra fluid in the tissues, and fat stores laid down to fuel breastfeeding. Very little of it is what people mean when they say putting on weight.

Energy needs rise by roughly 350 calories a day from the second trimester, which is one substantial snack rather than a second meal. Iron, calcium, protein and fibre all matter more than the calorie count.

The aches, and what actually helps

What	Why	What helps
Round ligament pain	Ligaments supporting the uterus stretch as it grows, and catch when you move suddenly	Move more slowly when standing or turning. Bend towards the pain. Warmth helps
Back pain	Centre of gravity shifts forward and the hormone relaxin loosens the pelvic joints	Flat supportive shoes, sleeping on your side with a pillow between the knees, and core-safe prenatal exercise
Heartburn	Progesterone relaxes the valve at the top of the stomach and the uterus pushes upward	Smaller meals, nothing within three hours of lying down, propping the head of the bed up. Ask before taking antacids
Nasal congestion and nosebleeds	Blood flow to the mucous membranes increases substantially	Saline spray, humidity. Avoid decongestant sprays unless your doctor approves them
Leg cramps at night	Not fully explained, but circulation and mineral balance both play a part	Stretch the calf before bed, stay hydrated, and mention it so calcium and magnesium can be checked
Swollen feet and ankles	Fluid retention and pressure on the veins returning blood from the legs	Elevate the feet, avoid standing still for long periods, and move regularly
Bleeding gums	Hormones increase gum sensitivity and blood flow	Soft brush, keep flossing, and see a dentist. Dental work is safe and the second trimester is the best window

Swelling that is not routine Sudden swelling of the face or hands, rather than gradual swelling of the feet, is different. Combined with a bad headache, visual disturbance, or pain under the ribs on the right, it can indicate pre-eclampsia and needs same-day assessment. This is the main reason your blood pressure and urine are checked at every visit.

Travel, work, exercise and sleep

Travel is generally most comfortable now. Most airlines carry passengers to about 36 weeks. On long journeys, move hourly, drink water and consider compression stockings, because pregnancy raises clot risk.
Exercise: about 150 minutes a week of moderate activity. Walking, swimming and prenatal yoga suit most women. Avoid contact sport, fall risk and lying flat on your back for long stretches after roughly 16 weeks.
Sleep on your side from around 20 weeks, ideally the left, which improves blood flow through the main vein returning blood to your heart. A pillow between the knees does more than any pregnancy pillow marketed at you.
At work, raise heavy lifting, long periods standing, night shifts and chemical or radiation exposure with your employer. Everything else usually carries on as normal.
Dental treatment, including x-rays with abdominal shielding, is safe and best done now rather than deferred.

Warning signs in the second trimester

Call the same day Any vaginal bleeding. A gush or steady trickle of fluid. Regular tightenings before 37 weeks, particularly more than four in an hour. Severe or persistent headache, flashing lights or blurred vision. Pain under the ribs on the right side. Sudden swelling of the face or hands. Fever above 38 degrees. Burning on passing urine, which in pregnancy can progress to a kidney infection quickly. A clear reduction in movements once you have been feeling them regularly.

Fetal weight figures are from the WHO Fetal Growth Charts (Kiserud et al., PLOS Medicine 2017, CC BY 4.0). Weight gain ranges follow the widely used international recommendations by pre-pregnancy BMI category; your own target should come from your doctor. This guide is general information and does not replace individual medical advice.

Tools and guides for this stage

BMI Calculator

Indian and international cut-offs side by side, which decides your weight gain target.

Pregnancy Tests Guide

The anomaly scan and the glucose test explained properly, along with everything else.

First Trimester Guide

Weeks 1 to 12, week by week, if you want to go back over what happened.

Third Trimester Guide

Weeks 29 to 40. Kick counting, baby position, labour signs and the hospital bag.

Pregnancy Nutrition Guide

How much extra to eat, the nutrients that matter, and why tea timing decides your iron levels.

Pregnancy Warning Signs

Sorted by urgency: what means go now, what means call today, and what can wait for your next visit.

Due for your anomaly scan?

The window runs from 18 to 22 weeks and it is the most detailed look anyone takes at your baby before birth. If you are approaching it, or your glucose test is due, book in and get both done in the right window rather than late.

Second trimester questions we hear most

I am 21 weeks and have not felt the baby move. Should I worry?

Not yet, and there is usually a straightforward explanation. First-time mothers commonly feel nothing definite until 22 weeks, and an anterior placenta, meaning one lying on the front wall of the uterus, cushions the movements and can delay it by two or three weeks. Mention it at your next visit so it is documented and so the placental position can be confirmed. What matters more is the pattern once movements do start.

What exactly does the anomaly scan check?

It is a systematic examination of the brain, face, spine, heart, abdominal organs, kidneys, bladder and limbs, along with the placenta, cord and fluid volume, plus growth measurements. It takes 30 to 45 minutes and the sonographer will be quiet for much of it because they are concentrating. A normal scan is real reassurance about structure, but it cannot detect everything, and it says nothing about most genetic conditions.

Can I refuse the glucose tolerance test?

You can decline anything, but this is one worth doing. Gestational diabetes usually causes no symptoms whatsoever, South Asian women are at higher risk at lower body weights, and undetected it raises the risk of a very large baby and a difficult delivery. Most cases that are picked up are managed with diet alone. Declining means finding out the hard way, if at all.

How much weight should I have put on by now?

It depends on where you started, which is why there is a table rather than a number. For a woman in the normal BMI range, roughly 0.4 kg a week through the second and third trimesters, adding to 11.5 to 16 kg over the pregnancy. Indian cut-offs classify overweight from a BMI of 23 rather than 25, so many doctors here aim at the lower end. Ask yours for your target rather than working from a chart.

Is it safe to fly in the second trimester?

For an uncomplicated pregnancy, generally yes, and this is the most comfortable window to do it. Most airlines carry passengers up to about 36 weeks and their rules are usually stricter than the medical picture requires. The real considerations are clot risk on long flights, managed by moving, hydrating and compression stockings, and how far you would be from care.

Why do I get a sharp pain in my side when I stand up?

That is almost always round ligament pain. The ligaments holding the uterus in place are stretching as it grows, and they catch when you move quickly. It is sharp, brief, usually one-sided, and worse when you stand, turn or sneeze. Moving more slowly and bending towards the pain both help. Pain that is constant, severe, or comes with bleeding or fever is different and needs a call.

Can I find out if it is a boy or a girl?

No. Determining or disclosing fetal sex is a criminal offence in India under the PCPNDT Act, 1994. Every registered scan centre is bound by it, the report will not contain it, and no legitimate clinic will tell you. Be wary of anyone who offers.