Perinatologist is worried about recessive conditions as we live in religious group. he wants amniocentesis. what can that show?

Depends: There are now 100's of recessive conditions that can be diagnosed prenatally. It would not be economical to test for all of them though, so i'd ask what exactly s/he would look for. Also, consider whether you would do anything differently if you knew your baby had a recessive condition? Amniocentesis has a small risk of pregnancy loss, so it is worth considering the pros and cons of having it.

Microarray analysis!: Nowadays, meticulous genetic testing called microarray analysis can detect all sorts of autosomal recessive conditions that could affect your offspring's health/life. Amniocentesis can procure the fetal cells currently needed to achieve this level of testing at this time. In the future, all of this will be possible via maternal blood testing for fetal dna analysis (not currently available).