Pregnancy Calculator - Бесплатный онлайн-калькулятор

Pregnancy dating is the foundation of all prenatal care - every screening test, ultrasound scan, growth check and delivery decision depends on accurate gestational age. The most common method, used worldwide, is Naegele's rule: due date = first day of last menstrual period (LMP) + 280 days (40 weeks), assuming a 28-day cycle. This calculator implements Naegele's rule with cycle-length adjustment so women with shorter (21-25 day) or longer (29-35 day) cycles get a more accurate estimate than the standard formula provides.

The result is an Estimated Due Date (EDD) - emphasis on 'estimated'. Only about 5% of babies arrive exactly on their due date; the majority are delivered within 38-42 weeks. A first-trimester ultrasound (ideally between 8-12 weeks) is the gold standard for confirming pregnancy dating and typically refines the EDD within ±5-7 days. After confirmation, all subsequent prenatal care follows that ultrasound date. This calculator is most useful before the first prenatal visit, to know your approximate stage and plan accordingly.

Naegele's rule was developed by Franz Karl Naegele in the 1830s and remains the most-used pregnancy dating method despite advances in ultrasound. It works because human gestation, measured from LMP, averages 280 days (40 weeks) with relatively narrow variation across populations. For women with cycles other than 28 days, the calculator adjusts by adding (cycle length − 28) days - a 30-day cycle gets +2 days; a 26-day cycle gets −2 days. This adjustment matters most early in pregnancy when planning screening windows.

Pregnancy weeks count from LMP, not from conception. So when you're told 'you're 6 weeks pregnant', the embryo itself is roughly 4 weeks old - pregnancy clock starts 2 weeks earlier than the actual biological start. This convention exists because LMP is a verifiable date for most women, while exact conception date often isn't. Trimesters are defined as: Trimester 1 (weeks 1-12, organ formation), Trimester 2 (weeks 13-26, rapid growth), Trimester 3 (weeks 27-40+, final development and weight gain).

Key prenatal milestones tied to gestational age in India: First-trimester ultrasound (8-12 weeks) for dating and viability; Double Marker test (10-13 weeks) for chromosomal screening; Anomaly scan / Level II ultrasound (18-22 weeks) for major structural abnormalities; Gestational diabetes test (24-28 weeks); Tetanus vaccination booster (at 20 and 26 weeks for first pregnancy); Iron-folic acid supplementation through pregnancy; Pre-delivery checkup (37 weeks) for labour planning. Knowing your accurate week guides timing of all these.