Symptoms may not start for 6 to 12 hours after exposure to the ultraviolet light. Symptoms include: 1  A feeling that something is in the eyes (foreign body sensation). 2  Sensitivity to light (photophobia). 3  Tearing.
It is divided into three stages, called trimesters: first trimester, second trimester, and third trimester. Conception to about the 12th week of pregnancy marks the first trimester. The second trimester is weeks 13 to 27, and the third trimester starts about 28 weeks and lasts until birth.
A quarter of a year, one fourth, is three months, as in financial quarters. I don't know if there is a term for 4 months. 12 weeks in a trimester, 3 months in a trimester, 4 weeks in a month. since there is 3 trimesters and there is 40 weeks in a normal pregnancy that means approximately 13 weeks per trimester.