A pregnancy calculator helps expectant Canadian parents estimate their due date, track pregnancy milestones, and understand the timeline of fetal development from conception through birth. Knowing exactly where you are in your pregnancy helps you plan prenatal appointments, maternity leave, nursery preparation, and the many arrangements that come with welcoming a new child in Canada. How Due Dates Are Calculated in Canadian Obstetric Practice: The standard method is Naegele rule, which adds 280 days or 40 weeks to the first day of the last menstrual period. This assumes a regular 28-day cycle with ovulation on day 14. Due dates are estimates — only approximately 5% of babies are born exactly on the estimated date. Most births occur within two weeks before or after the calculated date, and any birth between 37 and 42 weeks is considered full term by Canadian obstetric standards. Pregnancy Trimesters and Key Canadian Healthcare Milestones: The first trimester from conception to 12 weeks includes the first prenatal visit with your family doctor or midwife, blood work, and the first ultrasound typically between 10 and 13 weeks for nuchal translucency screening. The second trimester from weeks 13 to 26 includes the detailed anatomy ultrasound between 18 and 20 weeks. The third trimester from 27 weeks through birth involves more frequent prenatal appointments and Group B Strep testing around 36 weeks. Maternity and Parental Leave Planning in Canada: Canada offers some of the most generous parental leave benefits in the world through Employment Insurance. In Ontario, employees are entitled to begin maternity leave up to 17 weeks before their due date with full job protection throughout the entire leave period. Standard parental leave of up to 35 additional weeks is available to either parent. The Canada Child Benefit After Your Baby Arrives: Once your baby arrives, apply promptly for the Canada Child Benefit through the CRA. The CCB provides completely tax-free monthly payments to eligible families, reaching up to $7,787 per year for children under 6. Apply through the Automated Benefits Application at birth registration for the fastest processing. Both parents must file annual tax returns to continue receiving CCB payments each year. Ontario Prenatal Resources: Ontario provides the Healthy Babies Healthy Children program, prenatal nutrition programs, and coverage for specific medications through the Ontario Drug Benefit for eligible pregnant women. Use this calculator as your week-by-week reference throughout your pregnancy to understand what developmental milestones are expected at each stage and when to schedule key prenatal appointments. Share the results with your midwife or family doctor at your first prenatal visit so they can confirm the due date through clinical examination and ultrasound measurements and provide any necessary adjustments to your pregnancy timeline.