PREGNANCY GUIDE · PART 1 OF 3

First Trimester Guide: Weeks 1 to 12

What is forming, what you will feel, what to eat, what to avoid, and the signs that need a call today.

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

The first trimester does the least visible work and the most important. Almost every major structure in your baby is built between weeks five and ten, usually before the first appointment. This guide walks the twelve weeks in order, with the symptoms explained rather than just listed.

Where the first trimester sits in the forty weeksWeeks are counted from the first day of your last period, so you are already considered two weeks pregnant at conception and about four weeks pregnant when the first test turns positive.

What is actually happening inside

The first trimester does the least visible work and the most important. In twelve weeks a single fertilised cell becomes a fetus with a beating heart, a brain, a spine, limbs, a face and every major organ already in place. Almost all of that happens between weeks five and ten, which is why this is the window where alcohol, smoking, certain medicines and uncontrolled diabetes do the most damage, and why folic acid has to be started before you notice anything at all.

It is also why the first trimester carries the highest chance of miscarriage. Around one in five recognised pregnancies ends this way, and the great majority are caused by a chromosomal error present from the moment of conception. Nothing you lifted, ate, felt or forgot causes them.

What forms when, weeks 4 to 13The bars show the window in which each structure develops. Notice how much of it is finished before many women have had their first appointment.

Week by week, weeks 4 to 12

Sizes below are averages from ultrasound measurement, and the spread between healthy pregnancies is wide. Your own scan is the only measurement that means anything for you.

Week 4 — the test turns positive

The embryo is a ball of cells, roughly the size of a poppy seed, that has just implanted into the lining of the uterus. Implantation is what starts hCG production, which is what a home pregnancy test detects. Some women notice light implantation spotting around now and mistake it for an early period.

You may feel: nothing at all, or mild cramping and sore breasts. Most women feel nothing.

Week 5 — the neural tube forms

The neural tube, which becomes the brain and spinal cord, is forming and closing. This is exactly what folic acid protects, and why it is recommended from before conception rather than from the first appointment. The heart is a simple tube that has begun to fold.

You may feel: the first tiredness, and the beginning of nausea for some.

Week 6 — the heartbeat starts

The embryo is about 4 mm, the length of a grain of rice, and the heart starts beating, usually visible on a transvaginal scan from around now. Arm and leg buds appear as small paddles. The face begins as dark spots where the eyes will be.

You may feel: nausea, sore breasts, needing to pass urine more often, and a level of tiredness that surprises people.

Week 7 — the brain grows fast

About 10 mm. Brain tissue is growing at an extraordinary rate, and the head is disproportionately large as a result. The umbilical cord is formed and working. Kidneys are in place and will soon begin producing urine.

You may feel: peak nausea for many women, along with a heightened sense of smell that makes it worse.

Week 8 — from embryo to fetus

About 16 mm. Fingers and toes are present but still webbed. Upper lip, nose and eyelids are forming. From the end of this week the term changes from embryo to fetus. Most first antenatal visits happen somewhere between now and week 10.

You may feel: bloating, constipation, mood swings, and food aversions that appear overnight.

Week 9 — movement begins

About 23 mm. The fetus starts to move, though far too faintly for you to feel it. Elbows can bend. External genitalia are forming but not yet distinguishable. Essential organs are all present in basic form.

You may feel: the uterus is now roughly the size of a large orange, though nothing shows from outside.

Week 10 — the critical window closes

About 31 mm. The most vulnerable period for major structural development is finishing. Fingers and toes have separated. Tooth buds are forming. From here the work shifts from building to growing.

You may feel: nausea often starts to lift for some women, though for many it runs on to week 14 or beyond.

Week 11 — the NT scan window opens

About 41 mm. The head is still around half the total length. The fetus can open and close its fists and is beginning to swallow amniotic fluid. The nuchal translucency scan can now be done, and the window runs to 13 weeks and 6 days.

You may feel: a little more energy returning, and the first hint of a waistline change.

Week 12 — the end of the first trimester

About 54 mm, or roughly the size of a lime. All major organs are formed. Fingernails are appearing. Reflexes are developing, so the fetus will move if prodded during a scan. The risk of miscarriage drops sharply from this point.

You may feel: noticeably better, in most cases. This is the week many women choose to tell people.

The symptoms you are most likely to get

Almost everything on this list is caused by the same two things: a very rapid rise in hCG and progesterone, and a large increase in blood volume. Knowing the mechanism makes most of the symptoms less alarming.

Symptom	Why it happens	What actually helps	Call if
Nausea and vomiting	Rising hCG, made worse by a heightened sense of smell	Small frequent meals, dry carbohydrate before getting up, ginger, vitamin B6 if your doctor agrees	You cannot keep fluids down for 24 hours, or you are losing weight
Exhaustion	Progesterone is sedating, and your body is building a placenta from scratch	Sleep when you can, iron-rich food, and accepting that this is temporary	It comes with breathlessness or dizziness, which can mean anaemia
Sore, heavy breasts	Hormonal preparation of the milk ducts	A well-fitted supportive bra, including at night	One breast is red, hot or painful in one spot
Frequent urination	More blood to filter, and the uterus pressing on the bladder	Do not cut fluids, cut caffeine instead	It burns or stings, which suggests infection
Constipation and bloating	Progesterone slows the whole digestive tract	Fibre, water, walking, and iron taken with vitamin C rather than tea	There is pain with it, or any bleeding
Food aversions and cravings	Not fully understood, but strongly linked to smell	Eat what you can keep down and worry about balance in the second trimester	You are craving non-food items such as mud or chalk
Mood swings	Hormones, exhaustion, and the size of the news	Saying it out loud to someone, and sleep	Low mood lasts more than two weeks or you feel unable to cope

Morning sickness, and when it stops being normal

The name is misleading. Around eight in ten women get some nausea, it can arrive at any hour, and evening is a common time for it. It typically starts around week 6, peaks around week 9, and eases between weeks 12 and 16. A minority carry it much longer, and a small number never get it at all, which is also completely normal and not a sign that anything is wrong.

Eat before you feel hungry. An empty stomach makes nausea worse, which is why it is often worst first thing.
Keep dry biscuits or roasted chana by the bed and eat a little before you sit up.
Separate fluids from food by about half an hour, and sip rather than gulp.
Cold food smells less than hot food, and smell is the main trigger for most women.
Ginger has reasonable evidence behind it. Ask before taking any anti-nausea medicine, including ones sold without prescription.

When nausea is no longer just nausea Hyperemesis gravidarum is persistent vomiting that stops you keeping fluids down and causes weight loss and dehydration. It is not a severe version of normal morning sickness to be endured, it is a condition that needs treatment, sometimes with fluids given in hospital. Signs to act on: no urine for eight hours or very dark urine, dizziness on standing, losing weight, or vomiting everything for a full day.

What to eat, and the supplements that actually matter

You do not need extra calories in the first trimester. What rises sharply is your requirement for specific nutrients, at exactly the point when nausea is making balanced eating hardest. If you can only manage a few things, prioritise the supplements and let the diet catch up in the second trimester.

What	Why it matters now	Where it comes from
Folic acid	Reduces neural tube defects. The tube closes by about week 7, so this is the one supplement that works best before you know	A daily tablet, usually started before conception and continued through the first trimester. Dose is higher if you have diabetes, epilepsy or a previous affected pregnancy
Iron	Blood volume rises by almost half. Anaemia is very common in Indian pregnancies and causes much of the exhaustion	Supplement as prescribed, plus green leafy vegetables, dates, jaggery and pulses. Take with vitamin C, not with tea or coffee
Calcium and vitamin D	Skeletal development draws on your stores, and deficiency is widespread in urban India	Supplement as prescribed, plus dairy, ragi, sesame and some sunlight
Protein	Tissue building for both of you	Dal, paneer, eggs, curd, soya, chicken and fish that is low in mercury
Iodine	Needed for fetal brain development, particularly in the first trimester	Iodised salt, which is the reason it is iodised

One supplement to be careful with Do not take a general multivitamin on top of your prenatal tablets without asking. High-dose vitamin A, in the retinol form found in some supplements and in liver, can harm a developing baby. Prenatal formulations are designed around this. Random additions are not.

What to avoid, and what you can stop worrying about

The genuine list is short. Most of what gets added to it is folklore, and carrying twenty unnecessary restrictions makes it harder to hold the five that matter.

Alcohol. No amount has been shown to be safe, and the first trimester is when the brain is forming.
Smoking, including passive smoking at home. It restricts blood flow to the placenta.
Raw or undercooked eggs, meat and fish, and unpasteurised milk or paneer made from it.
High-mercury fish. In India that mainly means shark, swordfish and king mackerel. Rohu, katla, pomfret and prawns in normal amounts are fine.
Any medicine, including painkillers, ayurvedic and homeopathic preparations, until you have checked. Paracetamol is generally the safe option for pain and fever, but ask about anything else.
Cat litter and raw garden soil without gloves, because of toxoplasmosis.

Things you can stop worrying about, because they do not cause miscarriage: normal exercise, sex in an uncomplicated pregnancy, ordinary lifting, reaching above your head, travelling, working, hot weather, papaya in normal amounts, and whatever you did in the two weeks before you knew.

Tests and appointments in the first trimester

The first visit usually happens between weeks 6 and 10. Expect it to be long, because most of the baseline work is done in one sitting.

Dating scan, which confirms the pregnancy is in the uterus, checks the heartbeat, counts how many there are, and sets your due date more accurately than any calculation.
Blood group and Rh factor, which decides whether you need anti-D injections later.
Complete blood count, which is largely about anaemia.
Thyroid function, because untreated hypothyroidism affects fetal brain development and is common in Indian women.
Screening for HIV, hepatitis B and C, and syphilis, all of which can be managed to protect the baby if known about.
Blood sugar, and a urine test for infection and protein.
The NT scan between 11 weeks and 13 weeks 6 days, combined with a blood test, which screens for chromosomal conditions.

Our pregnancy tests guide explains what each of these is looking for and what the results mean, including the screening tests that only give you a probability rather than an answer.

Warning signs that need a call today

Do not wait for your next appointment Heavy bleeding, or bleeding with cramping. Severe one-sided abdominal or shoulder-tip pain, which can indicate an ectopic pregnancy and is an emergency. Fever above 38 degrees. Fainting or severe dizziness. Burning on passing urine with fever or back pain. Vomiting everything for more than 24 hours. Any of these warrants a phone call the same day, not a wait-and-see.

Light spotting, on the other hand, occurs in around one in four pregnancies and most of those continue normally. Report it, but do not assume the worst. Mild one-sided twinges as the uterus grows and the ligaments stretch are also very common and usually mean nothing.

The part nobody prepares you for

The first trimester is often the hardest emotionally and the one you are least allowed to talk about, because many women have not told anyone yet. You feel unwell, you are exhausted, nothing shows, and you are carrying both excitement and the knowledge that this is the riskiest stretch. That combination is genuinely difficult and it is not a sign that you are ungrateful or unready.

Telling one or two people early, rather than waiting for the twelve-week mark, is worth considering. The convention of secrecy exists to spare you having to explain a loss, but it also means going through the worst of it without support. That is a trade-off you are allowed to make differently.

Fetal size figures are averages from routine ultrasound measurement and vary widely between healthy pregnancies. The fetal weight chart is from the WHO Fetal Growth Charts (Kiserud et al., PLOS Medicine 2017, CC BY 4.0). This guide is general information and does not replace advice from your own doctor.

Work out your dates, and read on

Due Date Calculator

Your due date from your last period, a scan, a conception date or an IVF transfer, with the realistic range around it.

Pregnancy Tests Guide

Every scan and blood test across the forty weeks, what each looks for, and what a screening result actually means.

Second Trimester Guide

Weeks 13 to 28. The anomaly scan, first movements, the glucose test and weight gain.

Pregnancy Myths and Facts

Twenty-three claims you will be told in India, checked against the evidence.

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.

Book your first antenatal visit

The first visit sets your dates, checks for the things that are easiest to treat early, and gives you somebody to ask. If you have had a positive test, somewhere between six and ten weeks is the right time to come in.

First trimester questions we hear most

I have no symptoms at all. Is that a bad sign?

No. Around two in ten women get little or no nausea, and symptom intensity does not track with how the pregnancy is going. Symptoms also come and go, and a day when you suddenly feel fine is not a warning. What matters is the scan and the heartbeat, not how rough you feel.

When exactly does morning sickness stop?

For most women it eases between weeks 12 and 16, having started around week 6 and peaked around week 9. A meaningful minority carry it into the second trimester and a small number the whole way. If it is stopping you keeping fluids down, that is a different condition called hyperemesis and it needs treating rather than waiting out.

I had a glass of wine before I knew I was pregnant. What now?

This is one of the most common worries we hear and the honest answer is that the first two weeks after conception operate on an all-or-nothing basis, before the placenta connects. Tell your doctor so it is on record, stop now, and do not spend the pregnancy on it. What matters is what happens from here.

Is spotting in the first trimester dangerous?

Light spotting happens in roughly one in four pregnancies and most of those continue normally. It can be implantation, a sensitive cervix, or nothing identifiable. Report it so it is documented and so anyone Rh negative gets the right injection. Heavy bleeding, bleeding with cramping, or one-sided pain is different and needs a call the same day.

How accurate is my due date?

A first-trimester dating scan is accurate to within about five days, which is far better than counting from your last period, especially if your cycles are irregular. If the scan date and the calculated date disagree by more than about a week, the scan wins. Our due date calculator shows both, along with the range either side.

Can I keep working, travelling and exercising?

In an uncomplicated pregnancy, yes to all three. Around 150 minutes of moderate activity a week is what current guidance recommends. Travel is usually most comfortable in the second trimester, mainly because you feel better. What changes is contact sport, anything with a fall risk, and heavy exposure to chemicals or radiation at work, which is worth raising with your employer.

What is the actual chance of miscarriage?

Around one in five recognised pregnancies ends in miscarriage, the large majority in the first trimester and the large majority caused by a chromosomal error present from conception. That number drops sharply once a heartbeat is seen on a scan, and again after twelve weeks. Nothing you lifted, ate or felt causes them, which is worth saying plainly because most women assume otherwise.