How Is the Due Date Calculated?

This calculator estimates your due date using one of the following methods:

• LMP Method: Assumes a 280-day (40-week) pregnancy for singletons, 266 days (38 weeks) for twins, or 252 days (36 weeks) for triplets from the first day of your last period.
• Ultrasound Method: Uses the ultrasound date and gestational age at that time to calculate LMP, then computes the due date.
• Conception Date Method: Estimates LMP as 14 days before conception, then calculates the due date.
• IVF Transfer Date Method: Calculates conception date based on transfer date and embryo age, then estimates LMP and the due date.

The calculator uses standard obstetric assumptions but may not account for individual variations.

What Is a Due Date?

A due date is an estimated date of delivery, typically 40 weeks from the first day of your last menstrual period for a singleton pregnancy. It helps you and your healthcare provider plan for your baby’s arrival, though only about 4% of babies are born on their exact due date.

Factors Affecting Your Due Date

Several factors can influence your actual delivery date:

• Cycle Length: This calculator assumes a 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, your due date may differ.
• Pregnancy Type: Twins or triplets often deliver earlier than singletons.
• Medical Conditions: Conditions like gestational diabetes or preeclampsia may lead to earlier delivery.
• Ultrasound Accuracy: Early ultrasounds can adjust your due date based on fetal measurements.

Understanding Pregnancy Trimesters

Pregnancy is divided into three trimesters:

• First Trimester (0–12 weeks): Major organs develop, and you may experience symptoms like nausea.
• Second Trimester (13–27 weeks): The baby grows rapidly, and you may feel movement.
• Third Trimester (28–40 weeks): The baby prepares for birth, and you may feel more discomfort as delivery approaches.

Limitations of This Calculator

This calculator provides estimates based on averages and assumptions:

• It assumes a 28-day cycle and ovulation on day 14, which may not apply to everyone.
• It does not account for medical conditions that may affect delivery timing.
• IVF calculations assume standard embryo ages (3-day or 5-day); variations may affect accuracy.
• For precise due dates, consult your healthcare provider, especially if you have irregular cycles or are expecting multiples.

Always discuss your due date with your doctor or midwife for personalized care.