Gestational age and due date from last menstrual period
Estimates gestational age in weeks and days and due date from the last menstrual period (LMP), at a chosen reference date.
Calculate with transparency
Check the population, units and version. The result shows the formula or classification; it does not make an automatic treatment decision.
Preparing the form…
- Check the method
- Enter the data
- Check the result
Method · Limits of application
ACOG Committee Opinion 700/2017: LMP+280 days; calendar Naegele shown separately
According to ACOG 700/2017, dating should consider the last menstrual period and the first accurate ultrasound, with documentation of the best obstetric estimate. A pregnancy without ultrasound confirming or revising the estimated due date before 22 0/7 weeks is considered suboptimally dated. Later changes to the due date require exceptional circumstances; for research, using the last menstrual period alone is not recommended when a better obstetric estimate exists.
Conditions of use
Check the population, units, inclusion and exclusion criteria, and version in the original source. A result alone does not establish a diagnosis, discharge decision or prescription.
Documented parameters
- Last menstrual period: day
- Last menstrual period: month
- Last menstrual period: year
- Reference date: day (blank = today)
- Reference date: month
- Reference date: year
6/6 reference cases checked. Numerical tests are not clinical validation.
Relationship with cancer research
General context — relationship to be defined
A resource for general clinical contexts. This edition does not assign a specific oncological relationship; selecting it for a study requires a justified question, population and purpose.