Due Date Calculator

Most medical professionals use Naegele's Rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). Our 2026 auditor also synchronizes for varying cycle lengths and IVF transfer dates.

No. A due date is an estimated benchmark. Only about 4% of babies are born exactly on their due date. Most births occur within a week before or after the audited 40-week mark.

IVF calculations are more precise. For a Day 3 embryo transfer, add 263 days; for a Day 5 transfer, add 261 days to provide a technically superior audit compared to LMP-based methods.

Ultrasounds in the first trimester (up to 13 weeks) are the most accurate for dating. If the ultrasound differs by more than 7 days from your LMP audit, clinical protocol typically prioritizes the ultrasound.

Pregnancy is clinically defined as 280 days. 9 calendar months total roughly 39 weeks, but the standard medical audit includes the two weeks prior to conception (starting from LMP), totaling 40 weeks.

The 'Golden Month' refers to the first 30 days postpartum, but in prenatal auditing, it often signifies the critical final month where fetal lung maturation and adipose tissue accumulation peak.

While precise, many individuals do not know their exact conception date due to the viability of sperm (up to 5 days). The LMP method remains the institutional standard for this reason.

We track the neural tube closure (Week 4), fetal movement (Quickening, Week 16-20), and viability benchmarks (Week 24) using 2026 clinical standards.