Pregnancy Due Date Calculator

Due date calculators provide estimates based on a standard 280-day pregnancy length. However, only about 5% of babies are born on their exact due date. Most babies (about 80%) are born within 2 weeks before or after the estimated due date. The accuracy depends on having regular menstrual cycles and remembering the exact LMP date. For women with irregular cycles, early ultrasound dating may be more accurate.

Naegele's Rule is the standard method for calculating pregnancy due dates, developed by German obstetrician Franz Naegele. It adds 280 days (40 weeks) to the first day of your last menstrual period. This calculation assumes a 28-day menstrual cycle with ovulation occurring on day 14. While widely used by healthcare providers, it may not be accurate for women with cycles shorter or longer than 28 days.

Schedule your first prenatal appointment as soon as you know you're pregnant, ideally between 6-10 weeks of pregnancy. Early prenatal care is crucial for monitoring both mother and baby's health. Your healthcare provider will perform initial blood tests, discuss prenatal vitamins, review medical history, and establish a care plan. Don't delay - early care can help identify and prevent potential complications.

Pregnancy is divided into three trimesters: First trimester (1-12 weeks) involves major organ development, with common symptoms like morning sickness and fatigue. Second trimester (13-26 weeks) is often the most comfortable period, with increased energy and baby movements becoming noticeable. Third trimester (27-40 weeks) involves rapid baby growth, preparation for delivery, and more frequent prenatal visits. Each trimester has specific milestones and recommended care.

Yes, due dates can be adjusted based on ultrasound measurements, especially if there's a significant difference from LMP calculations. Early ultrasounds (performed before 20 weeks) are most accurate for pregnancy dating. Your healthcare provider may revise your due date if ultrasound measurements suggest a different gestational age. However, due dates are rarely changed after 20 weeks unless there are compelling medical reasons.

If you can't remember your LMP date, try the conception date method if you know when you conceived. Otherwise, consult your healthcare provider for an early ultrasound, which can accurately determine gestational age and estimate your due date. Ultrasound dating is particularly useful for women with irregular cycles or uncertain LMP dates. Keep track of your cycles in the future to help with any subsequent pregnancies.

A full-term pregnancy is 37-42 weeks from the last menstrual period. The American College of Obstetricians and Gynecologists defines categories: early term (37-38 weeks), full term (39-40 weeks), late term (41 weeks), and post-term (42+ weeks). Babies born between 39-40 weeks have the best outcomes, while babies born before 37 weeks are considered preterm and may need special care.

Several factors influence pregnancy timing: maternal age (older mothers may deliver later), previous pregnancy history (first babies often arrive late), multiple births (twins/triplets typically arrive 2-3 weeks early), medical conditions (diabetes, hypertension), stress levels, genetics, and lifestyle factors. Race and ethnicity can also play a role, with some populations having slightly different average pregnancy lengths.

Irregular cycles make LMP-based calculations less reliable because ovulation may not occur on day 14 of the cycle. If your cycles vary significantly in length (shorter than 21 days or longer than 35 days), conception date method or early ultrasound dating provides more accurate estimates. Track ovulation signs like basal body temperature or ovulation predictor kits if you have irregular cycles and are trying to conceive.

Key prenatal milestones include: first prenatal visit (6-10 weeks), genetic screening options (10-13 weeks), nuchal translucency ultrasound (11-14 weeks), anatomy scan (18-22 weeks), glucose screening test (24-28 weeks), third trimester growth scans (28-32 weeks), Group B Strep test (35-37 weeks), and weekly visits starting at 36 weeks. Your healthcare provider will guide you through the specific timing and necessity of each test.