PIP: The routine use of sonographic assessment of gestational age prior to elective late abortions should be encouraged for both fetal and maternal interests. The Supreme Court has upheld the right to abortion before viability and has held that not all second trimester abortions must be performed in hospitals. Viability is a presumptive and predictive term when used to describe a fetus in utero. In very premature newborn infants, survival is usually expressed as a function of birth weight because of the lack of standardization of gestational age assessment. It is very unusual for an infant with a birth weight less than 600 g to live, but a healthy infant with a birth weight greater than 600 g has a reasonable chance of survival if a modern intensive care unit is available. According to intrauterine and extrauterine growth curves, this birth weight corresponds to a gestational age of 23-24 weeks, but infants surviving at very low birth weights probably represent more mature fetuses with intrauterine growth retardation. For late abortions, the inherent inaccuracies of menstrual history and clinical sizing do not preclude the possibility of confusing a fetus that is not yet viable with a potentially viable fetus. Determination of biparietal diameter prior to late 2nd trimester abortion seems warranted since obstetric ultrasound is now readily available. A biparietal diameter measurement between 18-24 menstrual weeks is reliable within 10 days using 95% confidence limits. Based on biometric studies, a biparietal diameter of 57 mm to 61 mm and a femur length of 42 mm to 44 mm correspond to a mean gestational age of 24 weeks. Other sonographic measurements such as head perimeter and orbital measurements could also be used. In case of pregnancy termination, the method of termination should be based on accurate assessment of the duration of pregnancy.