The Pregnancy Calculator can estimate a pregnancy schedule based on the provided due date, last period date, ultrasound date, conception date, or IVF transfer date.
Pregnancy Term & Due Date
Pregnancy represents the state (~9 months) during which offspring develop inside a woman. Childbirth typically occurs approximately 38 weeks after conception, or about 40 weeks after the last menstrual period (LMP). The World Health Organization (WHO) defines a normal pregnancy term as lasting between 37 and 42 weeks.
Only about 4% of births occur on the exact estimated due date (EDD), 60% occur within one week, and nearly 90% occur within two weeks of the due date. While you can be confident of delivery within this window, predicting the exact day is not possible.
Pregnancy Detection
Pregnancy is detected by recognizing signs (such as a missed period, fatigue, morning sickness, and frequent urination) or using biomarkers. Clinical blood or urine tests can detect the hormone hCG (human chorionic gonadotropin) starting 6 to 8 days after fertilization. Home urine tests are highly accurate, convenient, and cost-effective compared to clinical alternatives.
Pregnancy Management Guidelines
The FDA classifies medications into categories based on potential maternal benefits vs. fetal risks:
• Category A: Controlled studies show no risk to the fetus in the first trimester.
• Category B/C/D: Graduating levels of potential risk or lack of human study data.
• Category X: Studies demonstrate proven fetal abnormalities; risks clearly outweigh any potential benefits.
The Institute of Medicine (IOM) recommends overall weight gain targets depending on the mother's pre-pregnancy Body Mass Index (BMI):
| Pre-pregnancy Weight Status | BMI Range | Recommended Gain |
|---|---|---|
| Underweight | < 18.5 | 28 to 40 lbs |
| Normal Weight | 18.5 – 24.9 | 25 to 35 lbs |
| Overweight | 25.0 – 29.9 | 15 to 25 lbs |
| Obese | > 30.0 | 11 to 20 lbs |
Aerobic and strength exercise helps maintain physical conditioning and decreases the rate of C-sections. The ACOG recommends continued physical activity for uncomplicated pregnancies. Stop exercising and seek medical attention if you experience: vaginal bleeding, dizziness, shortness of breath, headache, chest pain, amniotic fluid leakage, or decreased fetal movement.
Pregnancy requires increased micronutrients. Key supplements include Folic Acid (Vitamin B9), which significantly reduces neural tube defects, and DHA (Omega-3 fatty acids), crucial for baby's brain and eye development.
1. Jukic, AM, Baird, DD, Weinberg, CR, et al. 2013. "Length of human pregnancy and contributors to its natural variation." Human Reproduction 28(10): 2848-55.
2. Moore, Keith. 2015. "How accurate are due dates?" BBC News.
3. Institute of Medicine. 2009. "Weight Gain During Pregnancy: Reexamining the Guidelines." National Academies Press.
4. Davies, GA, Wolfe, LA, Mottola, MF, et al. 2003. "Exercise in pregnancy and the postpartum period." Journal of Obstetrics and Gynaecology Canada.
5. ACOG Guidelines for exercise during pregnancy and postpartum. British Journal of Sports Medicine.
How it Works & Formula
Estimates baby due dates, gestational age, and pregnancy milestone timelines based on the first day of the last menstrual period.
Practical Examples
LMP on October 1st results in an estimated due date of July 8th of the following year.
Frequently Asked Questions
How accurate is a pregnancy due date?
Only about 4% of babies are born on their exact due date. Most births occur within 1-2 weeks before or after the estimated due date.
How is the due date calculated from the last period?
The due date is estimated as 280 days (40 weeks) from the first day of the last menstrual period, adjusted for cycle length.
What are the trimesters of pregnancy?
First trimester: weeks 1-13. Second trimester: weeks 14-27. Third trimester: weeks 28-40. Each has distinct developmental milestones.