1 st Trimester AIUM/ACOG/ACR Guidelines  Transabdominal and/or transvaginal imaging  Appropriate labeling required  Uterus, including the cervix and adnexa, to evaluate for the presence of a gestational sac  If a gestational sac seen, its location documented  Gestational sac evaluated for presence or absence of yolk sac or embryo  Crown-rump length should be recorded  Presence or absence of cardiac activity recorded

1 st Trimester AIUM/ACOG/ACR Guidelines  Fetal number reported  In multiple gestation, amnionicity and chorionicity documented  Fetal anatomy appropriate for first trimester (unspecified)  Appearance of the nuchal region  Uterus, cervix adnexal structures, cul-de-sac evaluated  presence, location and size of adnexal masses  presence and size of leiomyomata  free fluid

1 st Trimester Establishing age of the pregnancy  For clinical (US) purposes, the first trimester is 2 weeks 0 days to 13 weeks 6 days  The terms menstrual age and gestational age are equivalent  Embryonic age starts at fertilization (2 weeks gestational age), concludes at the end of the 10th week (12 weeks gestational age) and is used by embryologists to describe human development, but is not useful in clinical practice

1 st Trimester  Pregnancy Dating  Gestational age based on time elapsed from start of last menses  Reported in weeks plus days  Embryonic age based on date of fertilization - always 2 weeks less than gestational age

1 st Trimester Maternal Serum hCG2 weeks 0 days to 3 weeks 0 days

1 st Trimester 3 weeks 0 days 3 weeks 2 days 4 weeks 0 days

1 st Trimester 4 weeks 0 days5 weeks 0 days

1 st Trimester  Gestational Sac  Often visible at 3 mm (4 weeks 6 days age)  Thick echogenic rim (chorion)  Intradecidual sign  Diameter reported as the average of three measurements  Enlarges approximately 1 mm mean diameter per day

1 st Trimester  Yolk Sac  Visible when GS is 10 mm (5 weeks 4 days)  First unequivocal sign of intrauterine pregnancy  Resides in the extra- embryonic space (coelom)  Measurements not useful

1 st Trimester  Embryo  Visible at approximately 3 mm (5 weeks 6 days)  Adjacent to yolk sac  Grows at approximately 1 mm per day

1 st Trimester  Embryo (Crown-Rump Length)  Best US predictor of gestational age between 7-12 weeks  Useful up to 14 weeks

1 st Trimester  Amnion  Visible between 6 and 7 weeks  Enlarges to obliterate the extra embryonic coelom and “fuses” to the chorion by 16 weeks

1 st Trimester  Embryonic Heart Activity  Visible when CRL is as small as 3 mm (5 weeks 6 days)  Rate starts very slow, and exceeds 160 in normal early pregnancy  Documentation with m- mode or cine preferable to Doppler

1 st Trimester Complications Criterion“Old” Standards“New” Standards Gestational sac mean diameter If >20 mm mean diameter and empty If >25 mm mean diameter and empty Yolk sacIf absent when GS is >10 mm If absent when GS is >20 mm Heart activityIf absent when GS is >16 mm or CRL >5 mm If absent when CRL >7 mm Ultrasound Obstet Gynecol 2011:38:489 Ultrasound Predictors of Abnormal 1 st Trimester Pregnancy

1 st Trimester Complications  Threatened abortion (miscarriage) - vaginal bleeding prior to viability  Inevitable abortion – abnormal gestational sac with no live embryo and dilated cervix  Missed abortion (retained products of conception) – embryo is dead for at least 8 weeks but no passage of tissue

1 st Trimester Complications  Extra-chorionic (subchorionic) hematoma  Between chorion and uterine wall (decidua)  Common in asymptomatic patients  Some correlation of size with clinical outcome  Size measured in 3 orthogonal dimensions

1 st Trimester Complications  Extra-chorionic (subchorionic) hematoma  Hematoma usually has low level echos  Because hematoma is extravascular, there is no flow (unlike placental venous sinus)

1 st Trimester Complications  Extra-chorionic (subchorionic) hemorrhage  But color Doppler is misleading because placental vascular sinuses have flow velocity below the threshold of most Doppler instruments  Hematoma is differentiated from a venous sinus with high resolution grey scale

1 st Trimester Complications  Ectopic Pregnancy  Most common in assisted reproduction (IVF etc.)  Presentation most common in 1 st trimester  Absence of intrauterine gestational sac is key  Presence of an intrauterine gestational sac does not exclude an ectopic  Presence of blood in peritoneal cavity (hemoperitoneum) helpful but not always present

1 st Trimester Complications  Tubal Ectopic  80% of ectopics in ampula or fimbrae  Hematoma in the tube (hematosalpinx) is subtle and must be actively searched for

1 st Trimester Complications  Interstitial Ectopic  3% of ectopics  Presentation commonly in early 2 nd trimester  Implantation in the tube between the between isthmus and endometrial cavity  US findings are a gestational sac adjacent to the uterus with absent or thin (<5 mm) myometrium

1 st Trimester Complications

1 st Trimester Multiple Gestation  Twins (“high risk”)  Perinatal mortality rate of dizygotic (fraternal) twins 3-7x singletons  Perinatal mortality rate of monozygotic (identical) twins 2-5x times dizygotic twins  Dichorionic diamniotic  Monochorionic, diamniotic  Monochorionic, monoamniotic

1 st Trimester Multiple Gestation  Dichorionic  Complete chorion around each twin  Easy diagnosis up to 12 weeks – chorion is thick and echogenic relative to amnion  Twin “peak” sign

1 st Trimester Multiple Gestation  Monochorionic  Diamniotic

1 st Trimester Multiple Gestation  Monochorionic  Monoamniotic

1 st Trimester Challenge