Trimesters, however, have a variability of a few weeks, so they should be thought of as general benchmarks.
We follow the same process in the third trimester, with a three-week difference.
Physical Exam Pregnancies can also be dated with a physical exam.
Medical professionals consider delivery premature when it occurs before 36 weeks, and extremely premature when it occurs before 28 weeks’ LMP.
It is also important to note that the phrase “late-term,” popularly used by the media to describe later abortions, has no medical meaning and is not used in any medical documentation.
Medical professionals use a standard set of up to three methods to date pregnancies: last menstrual period, ultrasound, and a physical exam.