अबस्तेत्रिक आलत्रासाउन्दखौ नैथि त्रायमेसतारनि 20 सपताफ्रामाव बांसिन सरासनस्रायै मावफुंनाय जायो ।
Obstetric ultrasounds are most commonly performed during the second trimester at approximately week 20 .