You have to give a proper ANC history & scan report to come to conclusion . Getting married to your cousin will not cause less AFI .
Next Steps
normally AFI should be 8 in 36 weeks of pregnancy .if it is too less your gynaecologist would have informed you as already 37 weeks , terminated pregnancy .
Health Tips
don't worry . drink plenty of water . get a obstetric Doppler study done for the wellbeing of the baby .