Calculate your pregnancy schedule and timeline based on due date, last menstrual period, ultrasound date, conception date, or IVF transfer date. Get accurate pregnancy information with detailed week-by-week breakdown.
Pregnancy calculations help estimate important dates throughout your pregnancy journey. A normal pregnancy lasts approximately 40 weeks (280 days) from the last menstrual period (LMP) or 38 weeks from conception. Understanding these calculations helps you plan for important milestones and medical appointments.
Different calculation methods are used depending on the available information. Each method has its own accuracy level, with ultrasound measurements typically being the most precise, especially when performed early in pregnancy.
Pregnancy is divided into three trimesters, each lasting approximately 12-13 weeks. The due date is an estimate, and only about 4% of babies are born exactly on their due date. Most babies (about 90%) are born within two weeks of the estimated due date.
Last Menstrual Period (LMP): The most common method, calculating from the first day of your last period. This assumes a 28-day cycle with ovulation occurring on day 14. The calculation adds 280 days (40 weeks) to the LMP date.
Ultrasound Dating: Uses fetal measurements to estimate gestational age. Most accurate when performed between 8-13 weeks of pregnancy. Later ultrasounds are less accurate for dating due to natural variations in fetal growth.
Conception Date: If you know when conception occurred, this method adds 266 days (38 weeks) to determine the due date. This is particularly useful for women who track ovulation or used fertility treatments.
IVF Transfer Date: For in vitro fertilization pregnancies, the transfer date is known precisely. The calculation depends on the embryo age at transfer (day 3, 5, or 6) and provides very accurate dating.
| Week | Trimester | Baby Development | Mother Changes | Medical Appointments |
|---|---|---|---|---|
| 4-6 | First | Heart begins beating | Missed period, early symptoms | Confirm pregnancy |
| 8-10 | First | Major organs form | Morning sickness peaks | First prenatal visit |
| 11-13 | First | Nuchal translucency screening | Energy may return | NT scan, blood tests |
| 18-22 | Second | Anatomy scan, gender reveal | Feeling baby move | Detailed ultrasound |
| 24-28 | Second | Rapid brain development | Glucose tolerance test | GDM screening |
| 32-34 | Third | Bones hardening | Increasing discomfort | More frequent visits |
| 36-37 | Third | Full-term approaching | Braxton Hicks contractions | Weekly check-ups |
| 38-42 | Third | Ready for birth | Labor signs | Monitoring for overdue |
First Trimester (Weeks 1-12): Morning sickness, breast tenderness, fatigue, frequent urination, food aversions, and mood changes. This is a critical period for organ development, and folic acid supplementation is essential.
Second Trimester (Weeks 13-26): Often called the "golden period" due to increased energy and reduced nausea. You'll feel baby's first movements, and the anatomy scan reveals baby's development and possibly gender.
Third Trimester (Weeks 27-40): Rapid weight gain, shortness of breath, back pain, and preparation for labor. Regular monitoring becomes more frequent as you approach your due date.
Regular prenatal visits are essential for monitoring both maternal and fetal health. The typical schedule includes monthly visits until 28 weeks, bi-weekly visits from 28-36 weeks, and weekly visits from 36 weeks until delivery.
Key screenings include blood tests for genetic conditions, glucose tolerance tests for gestational diabetes, group B strep testing, and regular monitoring of blood pressure and weight gain.
Studies show that fewer than 4% of births occur on the exact due date, 60% occur within a week of the due date, and almost 90% occur within two weeks. First pregnancies tend to go slightly past the due date, while subsequent pregnancies may be more likely to deliver earlier.