Two different methods can be used:

• Based on Last Period Date:
  • Pregnancy Week = (Today - Last Period Date) ÷ 7
• Based on Ultrasonography Date:
  • Pregnancy Start = Ultrason Date - Ultrason Week
  • Pregnancy Week = (Today - Pregnancy Start) ÷ 7

Trimesters:

• 1. Trimester: 0-12 weeks
• 2. Trimester: 13-26 weeks
• 3. Trimester: 27-40 weeks