US Pregnant Uterus Biophysical Profile Biophysical profile (BPP) is performed in the second and third trimesters, and there is no role for this in the first trimester. US Pregnant Uterus Transabdominal In the first trimester, the main goal of imaging is to confirm the presence and location of the gestational sacs, determine chorionicity and amnionicity, provide pregnancy dating, and document embryonic or fetal cardiac activity [9]. This is accomplished using transabdominal and TVUS. Once the in utero location of the gestational sac(s) is confirmed, recognition of possible multiple pregnancy is made and gestational age is determined [9]. Gestational age assessment is most accurate at the first US imaging and can be done using mean sac diameter or CRL measurements. In multiple gestations, all attempts should be made to establish the chorionicity and amnionicity at the earliest imaging encounter [9]. TVUS has the highest accuracy for this assessment. In a DC diamniotic gestation, 2 separate gestation sacs each with surrounding echogenic chorionic reactions are identified. A single gestation sac with peripheral chorionic reaction is seen with MC multiple gestations. The presence of thin intertwin membrane corresponds to diamniotic pregnancy. Very early on, the amnion may not yet have formed or be visible. Thus, lack of identification of an intertwin membrane does not necessarily indicate monoamnionicity. The intertwin membrane is typically identified by 10 weeks on TVUS. Although it has been suggested that the number of yolk sacs can be used as an indicator for assessing amnionicity, this determination can sometimes be erroneous [27]. Hence, attempt should be made to demonstrate a thin intertwin membrane as an indication of diamniotic pregnancy, which can more often be achieved by TVUS imaging or at the next US examination [9,27].
Multiple Gestations. US Pregnant Uterus Biophysical Profile Biophysical profile (BPP) is performed in the second and third trimesters, and there is no role for this in the first trimester. US Pregnant Uterus Transabdominal In the first trimester, the main goal of imaging is to confirm the presence and location of the gestational sacs, determine chorionicity and amnionicity, provide pregnancy dating, and document embryonic or fetal cardiac activity [9]. This is accomplished using transabdominal and TVUS. Once the in utero location of the gestational sac(s) is confirmed, recognition of possible multiple pregnancy is made and gestational age is determined [9]. Gestational age assessment is most accurate at the first US imaging and can be done using mean sac diameter or CRL measurements. In multiple gestations, all attempts should be made to establish the chorionicity and amnionicity at the earliest imaging encounter [9]. TVUS has the highest accuracy for this assessment. In a DC diamniotic gestation, 2 separate gestation sacs each with surrounding echogenic chorionic reactions are identified. A single gestation sac with peripheral chorionic reaction is seen with MC multiple gestations. The presence of thin intertwin membrane corresponds to diamniotic pregnancy. Very early on, the amnion may not yet have formed or be visible. Thus, lack of identification of an intertwin membrane does not necessarily indicate monoamnionicity. The intertwin membrane is typically identified by 10 weeks on TVUS. Although it has been suggested that the number of yolk sacs can be used as an indicator for assessing amnionicity, this determination can sometimes be erroneous [27]. Hence, attempt should be made to demonstrate a thin intertwin membrane as an indication of diamniotic pregnancy, which can more often be achieved by TVUS imaging or at the next US examination [9,27].