AFP LEVEL

hi im about 16 weeks perganant last week i had blood est serum screening and dr told me  the level of afp is slightly high is about 2.58, and may my baby was at risk of spina bifida or other abnormalities now i am so worried about the healthy of my baby i have some questions what is the normabel range of afp? does my afp is high? what is the problem cause for my baby? is it possible with high afp i have healthy baby? may the level of afp related to threathen misscarriage, subchoonic bleeding or hematoma , irregular LMP, utres polype, overian cyst , wrong estimation of gestation sac( how many weeks im perganant) or usage of folic acid or the other reason, as i had threathen misscarriage at 6 weekesand the size of hematoma was 3.11 cm , and i had one utres polype and one overian cycst which both removed by themseleves not by surgery and operation and i had irregular LMP, meanwhile my last LMP period was started at 21/12/2008 and was finished at 27 /12 / 2008, the ultrasoundscan told me just now my baby is 16 w and 4 days but i think i am 14 w or 15 w, as i had not sex with my husband during my periods ,meanwhile i take folic acid three months before my  preganancy and until the end of 10 or 11 weeks of my perganancy .please help me and answer my questions as iam so worried about my baby , is it possible the lack of folic acid cause this problem? shall i take folic acid again to avoide spina bifida or mental radation or any other abnormalities ,? would u pls tell the exact date of my gestation sac ( how many weeks i am perganant )? and the give me an appointment for scan next wek to see my baby. nd i am so worried about down syndrom (syndrome), maybe my baby have down syndrom (syndrome) or other abnormalities?