Liquor is the fluid within the womb that surrounds the baby. It has many functions like nutrient supply, shock
absorption, etc. Low liquor or low amniotic fluid index
(AFI) is called oligohydramnios
and may have many causes (eg: retarded growth of fetus, fetal kidney
problems, etc). However, your AFI is still within normal range, albeit a bit low for gestation.
Often, on a follow up scan, the liquor returns to normal. It would be advisable to check with your obstretician for any medical therapy if required. Also, it would be advisable for you to take as much rest as possible and have a good diet.
The fetal weight is normal for gestation. Placenta is often in the lower segment early in gestation and need not be a cause of worry. Often, on follow up scan after 7 months, the placenta moves to the upper segment.
Overall, there may not be much to worry about, especially since there is no obvious growth retardation or congenital anomaly. But, obstretic consultation and a follow up scan in 6-8 weeks maybe of significant help.