Question 1

What is the difference between gestational age and fetal age?

Accepted Answer

Gestational age is counted from the first day of the last menstrual period and is the standard used in clinical practice. Fetal age (also called conceptional age) is counted from the date of conception, which is typically about 2 weeks after the LMP. So fetal age is generally 2 weeks less than gestational age. When your doctor says you are 12 weeks pregnant, they mean 12 weeks gestational age, which is about 10 weeks since conception.

Question 2

How accurate is LMP-based gestational age?

Accepted Answer

LMP-based gestational age assumes a 28-day cycle with ovulation on day 14, which is not always the case. For women with irregular cycles, the LMP date may not accurately reflect gestational age. First-trimester ultrasound (crown-rump length measurement) is accurate to within 3-5 days and is considered the gold standard when there is a discrepancy of more than 7 days from the LMP estimate. Your healthcare provider may adjust your due date based on ultrasound findings.

Question 3

What are the key milestones in each trimester?

Accepted Answer

First trimester: heart begins beating at 6 weeks, all major organs form by 8 weeks, and the fetus is fully formed in miniature by 12 weeks. Second trimester: sex is visible on ultrasound around 18-20 weeks, the mother feels movement (quickening) at 16-22 weeks, and the fetus can hear sounds by 22-24 weeks. Third trimester: the lungs produce surfactant by 28-32 weeks, rapid weight gain occurs, and the baby reaches full maturity by 37-40 weeks.

Question 4

When is a baby considered full-term?

Accepted Answer

The American College of Obstetricians and Gynecologists defines term pregnancy as follows: Early term is 37 weeks 0 days through 38 weeks 6 days, Full term is 39 weeks 0 days through 40 weeks 6 days, Late term is 41 weeks 0 days through 41 weeks 6 days, and Post-term is 42 weeks 0 days and beyond. Babies born at full term (39-40 weeks) generally have the best outcomes. Elective delivery before 39 weeks is discouraged unless medically indicated.

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