Pregnancy typically lasts around 40 weeks from the last menstrual period, or approximately 38 weeks after conception. The World Health Organization defines a normal pregnancy term as lasting between 37 and 42 weeks.
Pregnancy Term & Due Date
The due date is an estimated date for childbirth, usually provided by an OB-GYN based on a sonogram or calculated from the date of the last menstrual period.
- Variability: Fewer than 4% of births occur on the exact due date. About 90% of births occur within two weeks of the due date.
- Factors Affecting Length: The actual length of a pregnancy can vary naturally based on factors like the mother’s age, weight, and the length of her previous pregnancies, although many sources of variation are not fully understood.
Pregnancy Detection
Pregnancy can be detected through noticing physical symptoms or by using pregnancy tests that detect hormone biomarkers.
Symptoms
Symptoms a woman may notice include:
- Missed menstrual period.
- Increased basal body temperature.
- Fatigue and nausea.
- Increased frequency of urination.
Pregnancy Tests
Tests detect the pregnancy hormone hCG (human chorionic gonadotropin).
[Image of a positive home pregnancy test]
- Clinical Blood Tests: These are the most accurate and can detect hCG earlier (six to eight days after fertilization) and in smaller quantities. They are, however, more time-consuming and expensive.
- Urine Tests (Home or Clinical): These are faster and less expensive than blood tests. Home pregnancy tests are generally not less accurate than clinical urine tests.
Pregnancy Management
Proper management of health factors is crucial during pregnancy, including medication use, weight gain, exercise, and nutrition.
Medication
In the U.S., the Food and Drug Administration (FDA) classifies drugs into categories (A, B, C, D, and X) based on potential fetal risk versus maternal benefit:
- Category A: Positive benefits for the mother with low risk to the fetus.
- Category X: Proven, significant fetal risks that outweigh any potential benefits.
- Action: A pregnant person should always consult their doctor regarding any medications they plan to use.
Weight Gain
Weight gain is necessary for fetal development, affecting the weight of the baby, placenta, and extra circulatory fluid. Weight management is important as both insufficient and excessive gain can lead to complications like the need for a cesarean section (C-section) or gestational hypertension.
[Image of a chart illustrating recommended weight gain during pregnancy based on pre-pregnancy BMI]
The Institute of Medicine (IOM) provides guidelines based on pre-pregnancy Body Mass Index (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
Exercise
Regular aerobic and strength-conditioning exercise is often recommended.
- Benefits: Helps maintain physical fitness and may decrease the risk of C-sections.
- Safety: For uncomplicated pregnancies, fetal injuries due to exercise are unlikely. Women who exercised regularly before pregnancy can usually continue high-intensity programs.
- Caution: A pregnant woman should consult their doctor if they experience symptoms like vaginal bleeding, dizziness, shortness of breath, decreased fetal movement, or chest pain.
Nutrition
Pregnancy requires increased energy and specific micronutrient requirements.
- Folic Acid (Vitamin B9): Helps decrease the risk of certain birth defects.
- DHA Omega-3: Essential for proper brain and retinal development; must be obtained through the placenta or breast milk as infants cannot produce it efficiently.
- Action: Pregnant women should consult their doctors and/or dietitian to determine the best nutritional plan for their specific needs.