A patient present for her first initial OB visit after performing a home pregnancy test and gives a last menstrual period of about 8 weeks ago. She says she is not entirely sure of her dates, however because she has a long history of irregular menses. Which of the following is the most accurate of way of dating the pregnancy?

Ans. is c, i.e. Crown rump length on abdominal or vaginal examination Coming to Q N13: The question is asking about first trimester USG.Option a. A gestational sac can be first seen 2 weeks after LMP - incorrect as it is seen at 4 weeks, 5 days after LMPOption b. The accuracy of determining gestational age using ultrasound begins to decrease after first trimester--correct as the best time to determine gestational age is first trimester and therefore accuracy decreases.Option c. Yolk sac is the first sign of pregnancy on USG--Incorrect as the first sign of pregnancy on USG is gestational sac, first sign of intrauterine pregnancy is yolk sac.Option d. USG can be used to determine the sex of the baby yes USG can determine sex of the baby but not in first trimester Sex of the baby can be determined positively on USG at 14 weeks.