The gestational age is recorded as the pregnancy progresses. Just as a downward scan can see any trends during the pregnancy, a scan horizontally will give a snapshot of each whole visit.
Urine Dipstick Tests
Protein and sugar (glucose) spilling in the urine are the most noteworthy items that screen you for the two most famous complications of pregnancy, Pregnancy Induced Hypertension (PIH or preeclampsia) and gestational diabetes (GD). These are usually graded as a 1+ to 4+ scale, or negative. Protein is a bit quirky, and a trace of protein is usually ignored. Higher recordings will prompt a 24-hour urine collection to actually count the amount of protein (a test deemed accurate as compared to this crude dip test).
It's not hard to get a positive glucose reading from your urine if you were naughty and had two donuts for breakfast. But spilling sugar enough to register on the dipstick is abnormal in the absence of any recent high calorie crimes. Typically, the screen for gestational diabetes is around the beginning of the third trimester, but spilling sugar anytime during the second trimester may prompt an earlier screen in addition to the traditional 26-week glucola test.
A sudden jump beyond which can be explained by diet alone is usually the result of a sudden fluid retention. Fluid is normal to some extent in pregnancy, but when accompanied by blood pressure increases and protein in the urine can be a sign of PIH.
The second trimester has a bit of a sudden weight jump at around 20 weeks. Since delivery involves bleeding at the time, your body will make extra blood (red blood cells and plasma) during the pregnancy. The extra blood helps keep you out of dangerously anemic territory in the postpartum period. During this mid-pregnancy phase, however, the extra blood is disproportionately produced, so at mid-pregnancy a six to eight-pound weight gain between visits is not unusual.