Fetal Age vs. Gestational Age: Understanding Weeks in Pregnancy

Question
I'm just curious about something... If someone gives birth to a fetus who is only 24 weeks is she really giving birth to a 22 week old fetus? My friend gave birth at 24 weeks and the baby lived just wanted to know if she was really 22 weeks or 24 weeks. her ultrasound said 24 weeks but i see everywhere on the net that ultrasounds go by LMP not the actual fetus age

Answer
Julie,


In every pregnancy, the fetus is always 2 weeks younger than you are weeks of pregnancy due to the way pregnancy length is calculated.  So, yes, if you delivered at 24 weeks of pregnancy, the fetus is actually 22 weeks.  If you're 38 weeks, the baby is 36 weeks, etc.


However, you would not say that you gave birth at 22 weeks (this would indicate the baby was 20 weeks and no child is viable at that age).  Measurements in pregnancy are always given in gestational age rather than fetal age to ensure that everyone is using a consistent system of measurement to avoid confusion.


Best,
Catherine