Question

و معمولا زنان باردار هنگامی به مراکز بهداشتی درمانی مراجعه می کنند که زمان مناسب برای پیش گیری از کمبودهای تغذیه ای این دوران گذشته  است ( 5)

Answer 1

And pregnant women usually visit medical health centers when the appropriate time (golden time) for prevention of nutritional deficiencies in this period has already passed. 

Answer 2

and usually, pregnant women go to health centers when the apt/appropriate time for prevention of undernutrition has passed.