Obstetrics Ultrasound course

Differentiate intrauterine gestational sac from a pseudo sac by eccentric location, rounded double walls with echogenic rim and peripheral flow, versus centric, elongated, single-walled pseudo sac with no flow.

Identify the gestational sac as a rounded eccentrically located structure in mid-upper uterine cavity, growing about 1 mm daily, with an echogenic border ring distinguishing it from a pseudo sac.

Identify the yolk sac as the first structure within the gestational sac confirming intrauterine pregnancy, appearing at five weeks, extra amniotic and attached to the embryo by the vitelline duct.

Observe the amniotic sac around week 18 as a small membranous structure continuous with the embryo, containing clear fluid, with the cavity obliterating by 12–16 weeks.

Track embryonic development from six to ten weeks, noting a rice-shaped embryo about 5.1 mm at six weeks, the gestational sac, and adjacent yolk sac on ultrasound.

Track fetal cardiac activity, heartbeat visibility at crown-rump length 2-4 mm, and how cleavage timing shapes twin types: dichorionic diamniotic, monochorionic diamniotic, monochorionic monoamniotic, and conjoined twins.

Differentiate multiple pregnancies on ultrasound by placental patterns and membranes: dichorionic diamniotic vs monochorionic diamniotic and monochorionic monoamniotic, noting lambda and Y signs and multiple corpora lutei.

Analyze early first-trimester triplets with triclinic anatomy and three placentas, thick membranes, and a lumbar spine separation that forms the epsilon sign for diagnosing triclinic pregnancy.

Learn to identify conjoined twins in early gestation using doppler and three-dimensional ultrasound, recognizing vascular connectivity, shared heart, and fusion patterns such as thoraco-omphalopagus, with differentiation from monoamniotic non-fused fetuses.

Learn to recognize and report pelvic masses in early pregnancy, including fibroids, corpus luteum cysts, ectopic and heterotopic pregnancies, and color Doppler findings.

Master early fetal biometry by crown–rump length from nine weeks onward, and use gestational sac diameter, biparietal diameter, head and abdominal circumferences, and femur length for dating.

Identify definitive and suspicious signs of early pregnancy failure, including miscarriage and embryonic demise, and explain chromosomal abnormalities as common causes.

Identify definitive signs of failed intrauterine pregnancy: no fetal heartbeat with crown-rump length ≥7 mm or gestational sac diameter over 25 mm with no embryo; follow up after two weeks.

Evaluate suspected pregnancy failure on ultrasound by interpreting embryo sizes around 3.9–4.1 mm, mean sac diameter, absence of heartbeat, and yolk sac and gestational sac findings, then recommend follow-up.

Identify sonography signs of pregnancy viability. Detect embryo with no cardiac activity and a yolk sac within a gestational sac 16–24 mm, with follow-up scans at 7–13 or 7–10 days.

Identify ultrasound signs of suspicious pregnancy, including slow embryonic heart rate and small gestational sac, with chorionic hematoma indicating high risk of embedding pregnancy failure.

Analyze transvaginal ultrasound examples of non-viable pregnancy: large yolk sac, absent cardiac activity, calcified yolk sac with empty amnion, mean sac diameter over 25 mm and euploidy as a cause.

Understand miscarriage in the first trimester, from threatened miscarriage to inevitable, incomplete, and complete forms. Use ultrasound to assess retained products of conception and identify missed miscarriage.

Assess postpartum bleeding with ultrasound to identify retained products of conception, using endometrial thickness, a solid heterogeneous mass, and Doppler vascularity patterns to differentiate from gestational trophoblastic disease and endometritis.

Examine subchorionic hematoma in obstetric ultrasound, its progression from echogenic to anechoic near the gestational sac, and differential considerations like retained products and arteriovenous malformation.

Differentiate extra chorionic fluid collections on ultrasound, including subchorionic hematoma or hemorrhage, co-twin demise, and amniotic separation, and assess placental position in the first trimester.

Identify chorionic bump on obstetric ultrasound as a focal protrusion of chorion with possible central necrosis and avascular Doppler features, noting single or multiple forms.

Explore ultrasound case scenarios illustrating embryonic demise, missed miscarriage, bradycardia, and other first-trimester findings, including gestational sac size, amnion, yolk sac, and retained products.

Explore gestational trophoblastic disease from premalignant complete and partial moles to malignant invasive mole, choriocarcinoma, placental site and epithelioid trophoblastic tumors, with ultrasound, doppler findings, and elevated beta hCG.

Explore premalignant forms of molar pregnancy, distinguishing complete and partial hydatidiform moles by beta-hCG, fetal presence, ultrasound patterns, and evacuation treatment, noting malignant transformation risk.

Navigate pitfalls in differentiating complete hydatidiform mole from hydropic degeneration in the first trimester, correlating ultrasound with beta-hCG and noting placental cystic and vascular findings.

Explore coexistent hydatidiform mole in a dizygotic twin pregnancy, showcasing a complete mole with a coexistent normal fetus and adjacent placenta on transabdominal ultrasound.

the malignant form of gestational trophoblastic neoplasia includes the invasive mole and gestational choriocarcinoma, which invade the myometrium and vessels, are highly vascular, and may resemble a complete hydatidiform mole.

Explains invasive mole after molar pregnancy, highlighting a highly vascular echogenic mass with cysts invading the myometrium, and persistent beta hCG elevations detectable by Doppler.

Choriocarcinoma can follow complete hydatidiform mole in 5–20 percent of cases. High beta-hCG and metastases occur, often to chest and lungs, sometimes brain or liver, hemorrhagic.

Study placental site trophoblastic tumor as a heterogeneous, cystic myometrial lesion with low beta hCG. A case with cesarean scar involvement, chemotherapy, and hysterectomy reveals epithelioid trophoblastic tumor.

Explain gestational trophoblastic neoplasia criteria by ultrasound, including lesion visibility, location (intracavitary or myometrial), size near four cm, and vascularity scoring with color doppler.

Assess chemotherapy resistance in gestational trophoblastic neoplasia by tumor size, lesion burden, and resistive index; diagnose and monitor with beta-hCG trends and choriocarcinoma criteria.

Explore the association between gestational trophoblastic disease and uterine vascular malformation, highlighting differential diagnosis, imaging findings, and management via angiography and embolization after molar pregnancy.

Theca lutein cysts arise with ovarian hyperstimulation and high beta hCG, forming ovaries up to 15 cm with septations, linked to invasive mole or choriocarcinoma, and regress after molar evacuation.

Explore how enhanced myometrial vascularity aids in differentiating gestational trophoblastic disease from retained products of conception and AVM, using low-resistance waveforms, beta hCG trends, and clinical correlation.

Identify tubal and non tubal ectopic pregnancy, including interstitial, isthmic, ampullary, and fimbrial sites, and ovarian, cervical, caesarian score, myometrium score, and abdominal locations.

Explore the incidence and diagnosis of ectopic pregnancy using transvaginal and transabdominal ultrasound, highlighting signs like empty uterus, vaginal bleeding, and tubal gestational sac with yolk sac.

Identify tubal ectopic pregnancy on ultrasound by definitive signs, such as adnexal sac, embryo, or cardiac activity, and probable signs such as a pseudo sac, decidual cast, and endometrial collections.

Examine the definitive signs of ectopic pregnancy on transvaginal sonography, including thick hyperechoic rim around the gestational sac with yolk sac, embryo, and possible cardiac activity.

Differentiate residual cyst from the gestational sac and identify early intrauterine signs by comparing the gestational sac with the pseudo sac, including echogenic rim and Doppler patterns.

Learn to identify a pseudo gestational sac on transvaginal ultrasound, characterized by intrauterine fluid with pointed margins and a single decidual lining, seen in suspected ectopic pregnancy.

Identify cul de sac findings on obstetric ultrasound, including hemoperitoneum from ruptured ectopic pregnancy and an ectopic gestational sac near the uterus with ovarian follicles.

Identify pitfalls in ultrasound diagnosis of ectopic pregnancy, such as intrauterine fluid with clot and corpus luteum mimics. Use color Doppler to distinguish ectopic from mimics.

Explore non-tubal ectopic pregnancies, including cervical, abdominal, ovarian, interstitial and corneal implants, plus a right rudimentary horn, with 3D transvaginal sonography clarifying interstitial involvement and distinguishing angular intrauterine pregnancies.

Learn to identify interstitial ectopic pregnancy on transvaginal ultrasound, including the interstitial line sign and thin endometrial mantle, with 3D ultrasound or MRI for equivocal cases.

Explore cervical ectopic pregnancy, a rare implantation below the internal os diagnosed mainly by ultrasound; MRI helps when needed, with signs including an empty uterus, barrel-shaped cervix, and Doppler flow.

Identify ovarian ectopic pregnancy linked to IUD use, where ultrasound aids diagnosis but resembles corpus luteum or hemorrhagic cysts. Surgical intervention confirms diagnosis by intraoperative findings and histopathology, providing treatment.

Understand abdominal ectopic pregnancy, its rare locations and ultrasound detection, with MRI as a diagnostic aid and beta hCG correlation guiding conservative management and outcomes.

Explore heterotopic pregnancy, the simultaneous intrauterine and ectopic pregnancy, increasingly seen with assisted reproductive techniques, and emphasize early diagnosis via ultrasound to reduce maternal morbidity and mortality.

Identify and differentiate non tubal ectopic pregnancy pitfalls, including intertwined and angular pregnancies, septate and bicornuate uteruses, and distinguishing cervical ectopic from miscarriage using ultrasound features.

Explore amniotic fluid volume, oligohydramnios, polyhydramnios, and discordant twins within the ABC approach for the second and third trimesters, including placenta, cord, Doppler, and fetal growth.

Explore amniotic fluid assessment, including fetal urination, pulmonary secretion, intramembranous and transmembrane exchanges, and gestational volume changes with measurement methods like the deepest vertical pocket and amniotic fluid index.

Assess amniotic fluid with subjective estimation and amniotic fluid index. Apply the mean maximum vertical pocket in four quadrants with perpendicular placement; avoid crossing parts, the umbilical cord, and squeezing.

Explore how the maximum vertical bucket and amniotic fluid index assess amniotic fluid status, with thresholds for oligohydramnios and polyhydramnios in second-trimester and twin pregnancies.

Identify oligohydramnios and polyhydramnios with MVP and AFI. Use Doppler to distinguish anhydramnios and evaluate causes such as rupture of membranes, placental insufficiency, and fetal renal issues.

Identify polyhydramnios using the amniotic fluid index and maximum vertical pockets, assess etiologies from maternal diabetes to fetal GI obstruction, and recognize related fetal and maternal risks.

Explore how polyhydramnios can compress the amniotic fluid and reveal the placenta on ultrasound, and assess its appearance when hydrops fetalis is present.

Assess amniotic fluid discordance in twin pregnancies by measuring maximum vertical pocket to identify oligohydramnios and polyhydramnios. Explain causes such as twin-to-twin transfusion syndrome, donor–recipient dynamics, and chorioangioma.

Explore echogenic amniotic fluid across trimesters, including vernix caseosa and meconium contamination in the second and third trimesters, intramembranous hemorrhage, chorioamnionitis, and related ultrasound findings.

Identify echogenic membranes in pregnancy and differentiate causes such as incomplete septum, uterine septum, amniotic sheath, intrauterine synechia, amniotic separation, circumvallate placenta, and amniotic bands, with ultrasound and MRI confirmation.

This lecture explains circumvallate placenta, a placental morphology variation where a small chorionic plate causes the amnion and fetal membranes to double around the edge.

Explore corneal amniotic separation, its timing with chorion and amnion fusion, ultrasound diagnosis in later gestation, and grading from mild to severe detachment, plus membrane hemorrhage and subplacental hematoma findings.

Explore amniotic band syndrome, where amniotic membrane constricts fetal limbs, creating a constriction ring and ultrasound clues to differentiate it from benign causes.

Ultrasound shows body stalk anomaly with a fetus adherent to the placenta and amnion, open peritoneum, and a large abdominal wall defect with extracorporeal liver, distinguishing it from omphalocele.

Explore ultrasound assessment of the cervix in pregnancy, comparing transabdominal, transradial, and transvaginal techniques, with emphasis on cervical length measurement, normal thresholds, and cerclage considerations.

Ask the patient to empty the bladder, position in lithotomy, insert the transvaginal transducer to obtain a sagittal view, withdraw slightly, avoid cervical pressure, and zoom to measure cervical length.

Evaluate gravid cervical measurements using single line, two line, and tracing methods to assess cervical length and funnel shapes (y, v, u), including internal os diameter and functional length.

During ultrasound cervical length measurement, avoid pressure on the cervix to prevent underestimation and funneling; maintain gentle transducer technique and repeat imaging over 3–5 minutes to account for dynamic changes.

A distended urinary bladder lengthens the cervical length on ultrasound, causing overestimation. Partial voiding normalizes the measure, underscoring the need to recheck with a less distended bladder.

Identify kissing uterine contractions in the lower uterine segment that mimic cervical dilation on ultrasound, re-examine until the contraction disappears, and confirm true cervical length with imaging and os clearance.

Assess true placenta previa versus pseudo previa caused by lower uterine segment contraction, using serial 20-minute scans to show initial placental coverage that resolves to pseudo previa.

Identify amniotic fluid sludge in the first two trimesters. Intraamniotic bleeding and cranioanencephaly associate with high alpha fetoprotein; late pregnancy shows vernix or meconium with a lung maturity sphingomyelin ratio.

Identify a cystic structure near the cervix that MRI confirms as a Gardner cyst, noting a normal cervix above and assess for placenta previa, vasa previa, and cervical polyps.

Recognize short cervix with funneling to the external os, amniotic fluid sludge, and particulate matter as risk factors for preterm birth, and cerclage outcomes vary.

Explore cervical cerclage for acute cervical insufficiency and prior preterm birth, including transvaginal and transabdominal techniques, placement details, removal timing, and ultrasound monitoring.

Identify pearls and pitfalls in obstetric ultrasound: distinguish cervical cancer from fluid, note mucus plugs and myometrial contractions can mimic funneling; avoid transducer overpressure as the cervix is dynamic.

Outline the normal placenta across the first to third trimesters, detailing chorionic tissue, cotyledons, and umbilical cord insertion, with lacunae and calcifications, and note previa, accreta, and abruption.

Explore normal placental grading from grade zero to grade three, detailing uniform tissue, chorionic bleed indentation, and basal and cotyledon calcifications across gestational ages.

Identify placenta locations—anterior, fundal, and posterior—and detect placenta previa versus low lying. Learn amniotic fusion versus separation after 14–16 weeks, and cord insertions including marginal, battledore, and vasa previa risks.

Examine the retro placental space using ultrasound and color Doppler to assess placental vascularity, identify normal and abnormal flow patterns, and recognize signs of placenta accreta.

Differentiate placental infarction from hematoma by a hypoechoic area with lack of blood flow and an echogenic rim for infarction; hematomas show mixed echogenicity and swirling blood in leaks.

Measure placental thickness after the second trimester, centrally near cord insertion; normal thickness is about 4 cm, up to 6 cm, with edges matching gestational age weeks plus one centimeter.

Assess placenta previa on ultrasound when the placenta covers the internal os of the cervix, using transvaginal imaging. Note low lying placenta and placental migration, and beware pseudo previa.

Explain how marginal sinus praevia indicates a mild placenta previa when the placental edge reaches the internal os, using color Doppler to confirm vascular lacunae.

Use ultrasound to detect placenta accreta spectrum with lacunae, loss of the clear zone, and thinning myometrium, especially when placenta previa or cesarean scar is present.

Placental abruption is premature placental separation, about 1% incidence; ultrasound may show subchorionic thickening or hematomas, but normal scans don’t rule it out, urgent triage for active bleeding.

Identify placental abruption patterns such as large marginal and retroplacental hematomas, retroplacental extension, and edge lifting, with ultrasound features, color doppler, and fetal demise at 32 weeks.

Identify chorioangioma as a highly vascular benign placental tumor often incidental. It can cause polyhydramnios, hydrops, or fetal anemia via hyperdynamic circulation, detectable by color Doppler.

Identify placental mesenchymal dysplasia as a rare, benign placental enlargement with grape-like vesicles on ultrasound, distinguishing it from molar pregnancy to prevent unnecessary termination, and note possible fetal overgrowth signs.

Explore bilobed placenta, a common bipartite placental morphology with two near-equal lobes, seen in up to 4% of pregnancies, and its risk of vasa previa and postpartum hemorrhage.

Explain the accessory loop of the placenta, its incidence, and differentiation from bilobed placenta. Use ultrasound and color doppler to identify the vascular connection to the placental disc.

Circumvallate placenta is a morphology variant with amnion and fetal membranes doubling back at the edge, seen in 1–7%, and distinguishable by ultrasound from amniotic shield or amniotic band syndrome.

Examine the placenta membranacea (placenta diffusa), an uncommon thin membrane variant around the periphery, linked to abnormal placental adhesions and may pose a differential diagnosis with marked polyhydramnios.

Explore placentomegaly and differential diagnoses such as hydrops and macrosomia, and examine amniotic separation, chorion-amnion non-fusion around 16–18 weeks, and amniotic band syndrome.

Explain the development of the umbilical cord and its vessels, Wharton’s jelly, and common abnormalities such as insertion, presentation, morphologic, vascular or cystic masses, plus abc approach in later trimesters.

Examine early fetal circulation and umbilical cord development, detailing vitelline duct and allantois roles, the normal cord with one vein and two arteries, and single artery implications for anomaly screening.

Explore mimics of a single umbilical artery with axial ultrasound and color Doppler to confirm two arteries around the bladder; review physiological gut herniation timing in early pregnancy.

Learn about umbilical cord insertion abnormalities, including central, marginal (eccentric), and lateral insertions, and their association with vasa previa. Understand normal central insertion and how deviations affect placental anatomy.

Identify central cord insertion and placental cord insertion as essential documentation in pregnancy, recognizing central and eccentric cord insertions as common and noting marginal and Forcade variants as potential pathologies.

Identify marginal cord insertion at the placental margin, with vessels traveling under the membrane toward the placenta and encroachment near the cervix that may threaten fetal compromise.

Learn about the rare 4K cord insertion, where umbilical vessels separate before reaching the placenta, with central, marginal, or eccentric insertions, including bilobed placentas and twin pregnancy implications.

Identify vasa previa as a presentation abnormality with fetal vessels over the internal os, types 1 and 2, confirmed by transvaginal color doppler ultrasound and helps distinguish mimics.

Use transvaginal ultrasound to identify cord presentation, showing a freely floating umbilical artery loop over the internal os with the three vessels visible for pre-delivery detection of prolapse risk.

Cord prolapse is an obstetric emergency requiring expeditious delivery for a viable fetus. Intrapartum monitoring aids diagnosis of occult or umbilical cord prolapse and prompt treatment to prevent cord compression.

Explore how increased Wharton's jelly thickens the umbilical cord, linking thick cords to anomalies and aneuploid fetuses. Note edema, allantoid changes, and proximal cord pseudocysts in late gestation.

Explore the forked umbilical cord, a rare anomaly in monochorionic diamniotic twins with venovenous anastomosis, where a single cord splits into two vessels, showing fenestration between veins on color Doppler.

Identify how umbilical cord distortions manifest as false note and true note, their clinical significance, and signs like hanging noose, with implications for fetal flow and labor management.

Learn about nuchal cord, or cord around the neck, including single loops (about 25%) and double loops (about 12.5%). Explore potential complications such as cord compression and growth restriction.

Single umbilical artery is a vascular abnormality in obstetric ultrasound, occurring in 0.4–1% of pregnancies and may be isolated or linked to anomalies, increasing risk of iugr and placental/cord abnormalities.

This lecture explains type two single umbilical artery, where the bladder lacks arteries and the artery arises from the aorta below the iliac celiac trunk, with sagittal view confirming the diagnosis.

Identify an umbilical vein varix on ultrasound as a focal dilatation exceeding 9 mm with the vortex about 15% larger, usually intrahepatic, with isolated cases having good prognosis.

Explore cystic and solid masses of the umbilical cord, including first-trimester cord cysts that commonly resolve (about 80%), and entities such as allantoic duct cysts, cord hematomas, and associated anomalies.

Identify myoma as a common incidental finding in pregnancy, note pain from degeneration or torsion, and follow large or multiple fibroids to anticipate spontaneous abortion, preterm delivery, or cesarean delivery.

Identify adenomyosis features on obstetric ultrasound, including myometrial thickening, intra myometrial decidualization, cystic changes, and diffuse vascularity, to differentiate from placental or gestational sac abnormalities.

Examine Müllerian duct anomalies and pregnancy patterns, including didelphys and septate uteri, rudimentary horn gestational sacs and ectopic risks, with sonographic signs such as echogenic fluid and bridging myometrium.

Provide ultrasound and MRI assessment of the acute abdomen in pregnancy, covering placental abruption, ovarian torsion, appendicitis, hydronephrosis, renal stones, fibroid degeneration, uterine rupture, HELLP-related hepatic complications, and imaging findings.

Explore obstetric neurovascular emergencies, including posterior reversible encephalopathy syndrome, cerebral venous thrombosis, subarachnoid hemorrhage, and pituitary apoplexy. Learn clinical features and imaging patterns essential for diagnosis in pregnancy and postpartum.

Assess trauma in pregnancy by examining the mother and fetus with a convex transducer, document viability, and monitor for placental abruption and fetal demise, including retroplacental hematoma and related findings.

Assess the fetal heart rate over a 30-minute biophysical profile, noting 15 beats per minute rises over 15 seconds twice, and observe fetal breathing with one 13-second episode.

Assess fetal tone by limb flexion and extension, dependent on an intact cerebral cortex; hypoxia and acidemia may halt movement, with one extension and return to flexion earning two points.

This lecture covers amniotic fluid assessment in obstetric ultrasound, including oligohydramnios and amniotic fluid index scoring. Normal 8–10 indicates good oxygenation; abnormal scores raise risk of fetal acidemia.

Assess placental maturity by grading (0–3) with calcifications and sono lucency; evaluate fetal kidney length and fetal lung maturity by comparing lung to liver echogenicity.

Identify signs of fetal lung abnormalities, including hyperexpanded lungs with inverted diaphragm in congenital high airway obstruction syndrome and lung sequestration with arterial supply, echogenic bowel and thalamic maturation markers.

Assess fetal skeletal maturity via distal femoral epiphysis, proximal tibial apophysis, and proximal humerus epiphyses, noting ossification centers and maturation timing.

Explore normal postpartum uterine involution in early, mid, and late stages, with ultrasound findings of enlarged uterus, thinning endometrium, and decreasing myometrial vascularity, plus attention to fluid, clots, and gas.

Examine the causes and ultrasound features of postpartum hemorrhage, including uterine atony, retained products, placenta accreta, endometritis, and uterine artery pseudoaneurysm with Doppler findings.

Identify common postpartum pain causes such as endometritis, hematoma, pelvic abscess, ovarian vein thrombophlebitis, adnexal torsion, and uterine rupture, with ultrasound findings guiding clinical diagnosis.

Identify the normal post cesarean ultrasound findings in the first postpartum week, including hysterotomy appearance, edema, sutures as echogenic lines, and the bladder flap, to avoid misdiagnosing hematoma or abscess.

Differentiate acute and chronic post cesarean complications, from hematomas and endometritis to placenta accreta and uterine fistula, illustrated by imaging findings of cellulitis and puerperal sepsis.

Bladder flap hematoma, a post‑cesarean complication, collects between the bladder and lower uterine segment; large hematomas compress the bladder and show gas foci on ultrasound indicating infection.

Identify post cesarean hematomas by location (rectus sheath, subfascial, abdominal wall) and classify CT type 1–3; recognize imaging features and urgent management for type 2–3 with resuscitation or embolization.

Differentiate uterine rupture and scar dehiscence on ultrasound by identifying a full-thickness tear with myometrium involvement versus thinning scar with intact serosa in cesarean patients.

Identify adhesions as a chronic complication that tether and distort the uterus. Observe an elongated uterus tethered to the bladder with absent sliding sign on dynamic ultrasound.

Learn to identify the cesarean scar niche on ultrasound, a myometrial defect at the lower segment; manage symptomatic cases with endoscopic or laparoscopic repair, or hysterectomy if necessary.

Explore scar endometriosis at cesarean section scars, presenting with cyclic pain; ultrasound reveals hypoechoic lesions with speculated margins and vascularity, sometimes forming a tract to the uterus.

Describe suture granulomas causing pain and swelling near cesarean scars, with ultrasound showing suture material surrounded by minimal fluid in the abdominal wall, and note cesarean scar ectopic pregnancy.

Uterovesical fistula, a true vesical fistula, presents with cyclic hematuria and possible absence of vaginal bleeding; cesarean sections are a common precursor, with MRI and ultrasound confirming the diagnosis.

Assess the cesarean scar niche in non-pregnant women with transvaginal gel infusion ultrasound, measuring length, depth, width, and residual myometrial thickness to classify branches and guide infertility risk discussions.

Measure the uterine segment scar in pregnancy at 11–14 and 36–38 weeks (abdominal or transvaginal) to assess rupture risk with a 3.5 mm threshold and evaluate thickness, texture, and vascularity.

Explore development of multiple pregnancies, detailing dizygotic and monozygotic twins, chorionicity and amnionic configurations, including dichorionic and monochorionic types and the rare conjoined and triplet embryos.

Assess chronicity and amnionicity in multiple pregnancies and identify chorionicity and placentation variants. Implement ultrasound surveillance and Doppler evaluation for monochorionic twins to monitor growth discordance and complications.

Identify signs of increased risk and major anomalies, such as nuchal translucency and euploidy risk, assess chorionicity, detect cord entanglement, and recognize twin pregnancy complications.

Identify chorionicity in pregnancy by counting placentas and amnions and recognizing signs such as two amnions with two placentas or a single placenta with one amnion, lambda and t signs.

Assess early twin pregnancies by recognizing dichorionic versus monochorionic placentation using ultrasound signs such as the twin peak sign and t sign, membrane thickness, and placental connections.

Explore ultrasound pitfalls in twin gestations, including monochorionic and diamniotic twins, monoamniotic twins, vanishing twins, and fetal demise signs like fetus papyraceus, with yolk sac and membrane assessment.

Explore twin to twin transfusion syndrome in monochorionic diamniotic pregnancies, detailing donor and recipient phenotypes, stage-based progression, and ultrasound markers from oligohydramnios and polyhydramnios to Doppler abnormalities.

Identify stage one twin-to-twin transfusion syndrome in monochorionic diamniotic twins by donor oligohydramnios and recipient polyhydramnios, with fluid discordance and distinct main vertical pockets; follow up within two weeks.

Identify stage two twin-to-twin transfusion syndrome in monochorionic diamniotic twins by absent donor bladder, oligohydramnios, polyhydramnios, and supportive color Doppler findings.

Identify stage ttts by Doppler: donor absent diastolic flow and reversed flow with abnormal ductus venosus and umbilical vein notching; recipient shows distended bladder and diastolic dysfunction with right-ventricle hypertrophy.

Identify stage four twin transfusion syndrome features, including hydrops with fluid in two compartments. Note polyhydramnios with ascites and doppler changes, such as umbilical vein notching and absent diastolic flow.

Stage five presents fetal demise in twin to twin transfusion syndrome; use ultrasound-guided fetoscopic laser ablation and monitor for amniotic leak, oligohydramnios, and amniotic separation.

TAPS is a twin anemia polycythemia syndrome variant in monochorionic twins; Doppler MCA velocities diagnose donor anemia and recipient polycythemia, with placental dichotomy and a five-stage progression.

Explore trap sequence, or twin reversed arterial perfusion, where acardiac twin lacks a heart and is perfused by the pump twin via reversed umbilical flow. Doppler signs guide radiofrequency ablation.

Explain twin dynamics in a monochorionic diamniotic pregnancy with isolated polyhydramnios in the recipient twin, while the co-twin has normal fluid and ultrasound findings, indicating a good prognosis.

Selective fetal growth restriction in twin gestation involves discordant growth due to placental sharing, with stage-specific Doppler patterns from preserved to reversed diastolic flow and to-and-fro flow.

Explore the impact of in utero twin demise in monochorionic pregnancies, detailing risks to the surviving twin, including ischemic brain injury, cardiomyopathy, and twin transfusion syndrome, and management.

Explore conjoined twins from monochorionic monoamniotic pregnancies, division after day 13, and fusion types such as thoracopagus, omphalopagus, and dicephalus, with color Doppler confirming single shared placenta and vascular connections.

Investigate fetus in fetu, a variant of monochorionic diamniotic twins where an abnormal fetus is enclosed within the other's body, presenting as a large cystic abdominal mass with calcified bones.

Explore triplet pregnancies in obstetric ultrasound, detailing monochorionic and dichorionic placenta with monoamniotic or diamniotic membranes, the twin peak sign, plus first-trimester follow-up for vanishing or reappearing twins.