GPA stands for gravida, para, and abortus.
Gravida is the number of pregnancies (no matter if they were carried to term or not). It would also include a current pregnancy.
Para is the number of viable births greater than 20 weeks (this number counts as 1 for twins, triplets, or multiples).
Abortus is the number of abortions, pregnancies lost no matter what the reason. The number would include miscarriages. The number would include induced abortions.
These are separated by commas. Transcribe them (abbreviated or spelled out) as dictated.
Example: G9, P9, A0 or gravida 9, para 9, abortus 0
TPAL system describes obstetric history of a woman.
T = term infants
P = premature infants
A = abortions
L = living children
These are separated by hyphens.
You will at times find GPA and TPAL dictated together.
Example: Patient is gravida 2, 2-0-0-2 or gravida 2, para 2-0-0-2 or G2, P2-0-0-2 or gravida 2-0-0-2.
You can find information on TPAL system and GPA in the Book of Style (third edition) starting on page 402.