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What Is Pregnancy and How Long Does It Last?

Pregnancy is the period when a baby grows inside a woman’s body, typically lasting about nine months. On average, childbirth happens 38 weeks after conception or about 40 weeks from the first day of the last menstrual period (LMP). The World Health Organization defines a full-term pregnancy as lasting between 37 and 42 weeks.

During a first prenatal visit, doctors often estimate the due date using a sonogram (ultrasound scan) or by calculating it based on the LMP. While this date is a good guideline, many factors affect the actual delivery day.

Studies show that:

• Less than 4% of babies are born exactly on their due date.

• Around 60% are born within a week of it.

• Nearly 90% are born within two weeks of the estimated due date.

So, while due dates offer a general timeline, predicting the exact birth day remains uncertain.

How Pregnancy Is Detected

Pregnancy can be confirmed through either physical symptoms or medical tests.

Common Early Symptoms:

• Missed periods

• Nausea or morning sickness

• Fatigue

• Frequent urination

• Higher basal body temperature

Types of Pregnancy Tests:

• Home urine tests: Convenient and affordable, these detect the pregnancy hormone hCG (human chorionic gonadotropin).

• Clinical urine tests: Done at a medical facility, but not necessarily more accurate than home tests.

• Blood tests: Can detect pregnancy earlier and measure exact hCG levels, but are more expensive and take longer to process.

Important Factors for a Healthy Pregnancy

Each pregnancy is unique, but there are key areas every expecting mother should focus on, including medication safety, healthy weight gain, exercise, and nutrition.

Medications During Pregnancy

Some medications can harm the baby during pregnancy. The FDA classifies drugs by risk:

• Category A: Safest

• Category X: Known risks outweigh benefits

Always talk to a healthcare provider before taking any medication while pregnant.

Recommended Pregnancy Weight Gain

Gaining weight during pregnancy is essential for the baby’s growth and development. However, gaining too much or too little can lead to complications like high blood pressure or the need for a C-section.

According to the Institute of Medicine, recommended weight gain varies by BMI:

• Normal 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

Use our Pregnancy Weight Gain Calculator to see your ideal weight range.

Exercise Guidelines During Pregnancy

Exercise can help maintain fitness and lower the risk of complications. Women who exercised before pregnancy can often continue, as long as the pregnancy is uncomplicated.

The American College of Obstetricians and Gynecologists (ACOG) states that regular activity is generally safe. However, stop and seek medical advice if you experience:

• Vaginal bleeding

• Chest pain or shortness of breath

• Dizziness or headaches

• Decreased fetal movement

• Muscle weakness or swelling

Nutrition Tips for Expecting Mothers

Nutrition plays a vital role in both the mother’s and baby’s health. Pregnancy increases the need for certain vitamins, minerals, and calories.

Key nutrients include:

• Folic Acid (Vitamin B9): Helps prevent birth defects

• DHA (Omega-3): Supports baby’s brain and eye development

Since every pregnancy is different, it’s best to work with a doctor or dietitian to create a personalized nutrition plan.

References

1. Jukic, AM et al. (2013). Length of human pregnancy and contributors to its natural variation. Human Reproduction.

2. Moore, K. (2015). How accurate are ‘due dates’? BBC News.

3. Institute of Medicine. (2009). Weight Gain During Pregnancy: Reexamining the Guidelines.

4. Davies, GA et al. (2003). Exercise in pregnancy and the postpartum period. Journal of Obstetrics and Gynaecology Canada.

5. Artal, R., O’Toole, M. (2003). Exercise during pregnancy. British Journal of Sports Medicine.

6. Lammi-Keefe, CJ et al. (2008). Handbook of Nutrition and Pregnancy. Humana Press.