At what gestational age is first trimester screening typically conducted?

First trimester screening is typically conducted between 11 to 13 weeks of gestation. This timing is critical because it allows for the measurement of certain biomarkers, such as nuchal translucency, maternal serum markers, and other factors that can help assess the risk of chromosomal abnormalities, including Down syndrome.

During this period, ultrasound can provide precise measurements of nuchal translucency, which is the fluid collection at the back of the fetus's neck, as well as the development of the fetus to ensure that it is progressing normally. Additionally, blood tests can be administered during this timeframe to evaluate specific hormone and protein levels, which contribute to the overall assessment of fetal well-being.

Conducting screening too early, such as at 8-10 weeks, would not provide accurate measurements necessary for risk assessment. Conversely, doing the screening later in the pregnancy, such as at 14-16 weeks or 17-20 weeks, would miss the optimal window for detecting certain conditions early enough for potential intervention and further testing decisions. Thus, the most appropriate and clinically relevant timeframe for first trimester screening is indeed between 11 and 13 weeks of gestation.