Pregnancy Week Calculator
Calculate your current week and day of pregnancy and see what is happening at this stage of development. Enter your last period or due date.
Week by Week Pregnancy Guide
How Pregnancy Weeks Are Counted
Pregnancy is counted from the first day of the last menstrual period (LMP), not from conception. This means you are 'two weeks pregnant' when you actually conceive. A full-term pregnancy is 40 weeks from LMP, but most babies arrive between 38–42 weeks. The dating scan at 11–13 weeks provides the most accurate gestational age and is used to adjust the due date if there is a significant discrepancy from LMP-based dating.
Trimester Breakdown
First trimester (weeks 1–13): all major organs form; highest miscarriage risk; morning sickness common. Nuchal translucency scan at 11–14 weeks. Combined test for Down's syndrome. Second trimester (weeks 14–26): anomaly scan at 18–21 weeks checks development in detail. Many women feel best now — energy returns, sickness eases, bump becomes visible. Third trimester (weeks 27–40): rapid growth and weight gain; growth scans from 28 weeks; birth plan; Group B strep test; full-term from 37 weeks.
Key Development Milestones
4 weeks: embryo implanted, size of a poppy seed. 8 weeks: all major organs forming, heartbeat detectable. 12 weeks: fingers and toes distinct, risk of miscarriage drops significantly. 16 weeks: sex may be identifiable on scan. 20 weeks: anomaly scan, baby is approximately 25cm. 24 weeks: threshold of viability — survival possible with intensive care. 28 weeks: eyes open, brain developing rapidly. 32 weeks: most systems mature, survival rate excellent. 36 weeks: most positions fixed, lungs nearly
NHS Antenatal Schedule
Typical NHS antenatal appointments for low-risk pregnancies: 8–10 weeks — booking appointment (full history, blood tests, urine). 11–14 weeks — dating scan + nuchal translucency. 16 weeks — routine appointment. 18–21 weeks — anomaly scan. 25 weeks (first baby). 28 weeks — blood tests (anaemia, gestational diabetes risk). 31 weeks (first baby). 34 weeks. 36 weeks — position checked. 38 weeks. 40 weeks (first baby). 41 weeks — sweep offered. Each appointment checks blood pressure, urine, baby's he
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