Final answer:
When the LMP is unknown, EDD can be determined using both fetal biometry calculations and ultrasound assessment.
Step-by-step explanation:
When the LMP (Last Menstrual Period) is unknown, the estimated due date (EDD) can still be determined using both fetal biometry calculations and ultrasound assessment. Fetal biometry involves measuring specific fetal parameters, such as the head circumference, abdominal circumference, and femur length, and using these measurements to estimate the gestational age and EDD. Ultrasound assessment can also be used to measure fetal parameters and assess the development and growth of the fetus, which can help determine the EDD.