**Question:** A mother does not remember the date of her last menstrual period and no antenatal ultrasound reports are available. Which of the following tools can be used to assess the gestational age of the neonate born to this mother?

A. Ballard score
B. Crown-rump length measurement
C. Nuchal translucency measurement
D. Amniotic fluid index

**Correct Answer:** C. Nuchal translucency measurement

**Core Concept:** Nuchal translucency (NT) is a routine ultrasound measurement used to assess the risk of chromosomal abnormalities in a fetus during pregnancy. In the first trimester, the NT measurement is performed by measuring the thickness of the fluid at the back of the neck, which is a simple, quick, and non-invasive procedure.

**Why the Correct Answer is Right:** When there are no ultrasound reports available, such as in the given scenario, relying on the Ballard score or crown-rump length measurement might not be accurate since they require ultrasound data. Nuchal translucency measurement, however, does not depend on these factors and can still provide valuable information.

**Why Each Wrong Option is Incorrect:**

A. Ballard score: The Ballard score is a neonatal assessment tool used to estimate gestational age and predict the probability of respiratory distress syndrome in preterm infants, not gestational age assessment in the mother's pregnancy.

B. Crown-rump length measurement: This measurement requires precise ultrasound data, which is not available in the given scenario.

D. Amniotic fluid index (AFI): AFI is used to assess amniotic fluid volume, not gestational age assessment in the mother's pregnancy.

**Clinical Pearl:** Ultrasound measurements, like nuchal translucency measurement, provide important information during prenatal care, even when other data is missing. In this case, the measurement of nuchal translucency can help estimate the risk of chromosomal abnormalities and potentially guide further management options for the mother and child.