The first 12 weeks of pregnancy are crucial. From managing morning sickness to understanding your first scans, here's your complete guide to the first trimester.
Congratulations — You Are Pregnant!
The first trimester (weeks 1–12) is one of the most significant periods of your pregnancy. Your body is undergoing profound changes, and your baby is developing at an astonishing pace — from a single fertilised cell to a fully formed foetus with heartbeat, limbs, and organs.
Week-by-Week Highlights
Weeks 1–4: The Foundation
Fertilisation occurs and the embryo implants in the uterine lining. Most women do not yet know they are pregnant. A home pregnancy test usually becomes positive around week 4–5.
Weeks 5–8: Early Development
The embryo's heart begins beating (around week 6). Nausea, fatigue, and breast tenderness often begin. Your first ultrasound (dating scan) is ideally done at 6–8 weeks.
Weeks 9–12: Becoming a Foetus
All major organs are formed. The embryo is now called a foetus. The nuchal translucency scan (combined with blood tests) is done at 11–13 weeks to screen for chromosomal conditions.
Common First Trimester Symptoms
- Morning sickness: Nausea (and sometimes vomiting) affects about 70–80% of pregnant women. Despite the name, it can occur any time of day.
- Fatigue: Your body is working hard. Rest as much as possible.
- Breast tenderness: Hormonal changes make breasts feel fuller and more sensitive.
- Frequent urination: Your kidneys are working harder and your uterus is growing.
- Food aversions and cravings: Common and usually harmless.
- Mild spotting (implantation bleeding): A small amount of light spotting around week 4 can be normal.
Essential Tests in the First Trimester
1. Blood group and Rh typing
2. Complete blood count (anaemia check)
3. Blood sugar (HbA1c)
4. Thyroid function (TSH)
5. Rubella immunity
6. HIV, hepatitis B, syphilis screening
7. Dating ultrasound (6–8 weeks)
8. Nuchal translucency + combined first trimester screening (11–13 weeks)
Nutrition in the First Trimester
Foods to eat:
- Iron-rich foods: spinach, lentils, lean meats
- Folate-rich foods: green leafy vegetables, fortified cereals
- Calcium: dairy, sesame seeds, tofu
- Protein: eggs, pulses, fish, chicken
Foods to avoid:
- Raw or undercooked meat and eggs
- Unpasteurised dairy
- High-mercury fish (swordfish, shark)
- Excessive caffeine (limit to <200mg/day)
- Alcohol — there is no safe level in pregnancy
Supplements to Take
- Folic acid (400–800 mcg/day): Essential for neural tube defect prevention, ideally started before conception
- Vitamin D: If levels are low
- Iron: If anaemic
Warning Signs to See Dr. Sanjana Immediately
- Heavy bleeding (more than a period)
- Severe abdominal cramps
- Fever above 38°C
- Severe vomiting that prevents you from keeping any food or fluid down (hyperemesis gravidarum)
- Burning or pain on urination (possible UTI, common in pregnancy)
Your First Appointment at Health Nest
At your first visit, Dr. Sanjana L will confirm your pregnancy, estimate your due date, review your health history, and order initial investigations. It is a good opportunity to ask all the questions you have been wondering about. There are no silly questions when it comes to your pregnancy.
Dr. Sanjana L, Obstetrician & Gynaecologist at Health Nest, HSR Layout, Bangalore, is here to guide you through every step of this beautiful journey.
Dr. Sanjana L
MBBS, MS (OB-GYN) · Gynaecologist at Health Nest, HSR Layout, Bangalore