Pregnancy Term & Due Date Calculator

Pregnancy refers to the period during which a woman carries one or more offspring in her uterus, typically lasting around 9 months. Childbirth usually occurs about 38 weeks after conception or 40 weeks from the first day of the last menstrual period. According to the World Health Organization (WHO), a typical pregnancy lasts between 37 and 42 weeks. During the first visit to an OB-GYN, a doctor will provide an estimated due date, often determined through an ultrasound. Alternatively, the due date can also be calculated based on the last menstrual period.

While the due date is an estimate, the exact length of pregnancy varies due to factors like maternal age, previous pregnancies, and maternal weight at birth. Studies show that fewer than 4% of births occur on the exact due date, with 60% occurring within a week and nearly 90% within two weeks of the expected date. Although we can estimate a likely range for birth, predicting the exact day with certainty remains impossible.

Pregnancy Detection Methods

Pregnancy can be detected either through pregnancy tests or by recognizing early symptoms such as a missed period, increased basal body temperature, fatigue, nausea, and frequent urination.

Pregnancy tests work by detecting specific hormones in the body, most commonly human chorionic gonadotropin (hCG), which is produced during pregnancy. Blood tests can detect pregnancy as early as 6-8 days after fertilization. Though more accurate, these tests are also more expensive and take longer to process compared to home urine tests. Clinical urine tests, while reliable, do not necessarily offer higher accuracy than home tests and may be more costly.

Managing Pregnancy: Key Considerations

Medication During Pregnancy

The use of medication during pregnancy should always be carefully considered due to its potential effects on fetal development. The U.S. Food and Drug Administration (FDA) categorizes medications based on the risk they pose to a developing fetus. Drugs that have low risks are categorized as “A,” while those with significant fetal risks are categorized as “X.” Always consult a healthcare provider before taking any medications during pregnancy.

Weight Gain During Pregnancy

Weight gain is a natural part of pregnancy and is essential for fetal development. Factors like the weight of the baby, placenta, additional circulatory fluid, and fat and protein stores contribute to this increase. Insufficient or excessive weight gain can lead to complications such as gestational hypertension or the need for a cesarean section. The Institute of Medicine recommends weight gain ranges based on a woman’s pre-pregnancy BMI:

Normal weight (BMI 18.5–24.9): 25–35 pounds
Underweight (BMI <18.5): 28–40 pounds
Overweight (BMI 25–29.9): 15–25 pounds
Obese (BMI >30): 11–20 pounds

Our Pregnancy Weight Gain Calculator helps track recommended weight gain for a healthier pregnancy.

Exercise During Pregnancy

Aerobic exercise during pregnancy is beneficial for maintaining fitness and may reduce the risk of complications such as C-sections. Pregnant women who exercised regularly before pregnancy can typically continue high-intensity exercise programs, provided they have an uncomplicated pregnancy. The American College of Obstetricians and Gynecologists notes that exercise is safe during pregnancy for most women but advises caution if symptoms like vaginal bleeding, dizziness, shortness of breath, or decreased fetal movement occur.

Nutrition During Pregnancy

Proper nutrition during pregnancy is crucial for both maternal and fetal health. Pregnant women have higher energy and specific micronutrient needs compared to non-pregnant individuals. Key nutrients like folic acid (Vitamin B9) help prevent birth defects, while DHA omega-3 fatty acids are essential for fetal brain and eye development. Pregnant women should seek guidance from their healthcare provider or dietitian to determine the best dietary approach for their unique needs.

Important Studies and References

Jukic, AM et al. (2013) – “Length of human pregnancy and contributors to its natural variation.” Human Reproduction.
Moore, Keith (2015) – “How accurate are ‘due dates’?” BBC.
Institute of Medicine (2009) – “Weight Gain During Pregnancy: Reexamining the Guidelines.” National Academies Press.
Davies, GA et al. (2003) – “Exercise in pregnancy and the postpartum period.” Journal of Obstetrics and Gynecology Canada.
Artal, R., O’Toole, M. (2003) – “Guidelines of the American College of Obstetricians and Gynecologists for exercise during pregnancy.” British Journal of Sports Medicine.
Lammi-Keefe, CJ et al. (2008) – “Handbook of Nutrition and Pregnancy.” Humana Press.