Twin Anomaly Scan at Dr. Essa Lab

Twin Anomaly Scan at Dr. Essa Lab

A Twin Anomaly Scan, often referred to as a mid-trimester target scan or level II ultrasound, is a highly specialized diagnostic imaging procedure performed during pregnancy, typically between the 18th and 22nd weeks of gestation. This comprehensive ultrasound examination is designed to evaluate the structural development, anatomical integrity, and overall well-being of both fetuses in a multiple pregnancy. Because twin pregnancies carry a higher risk of maternal and fetal complications compared to singleton pregnancies, this scan is a critical milestone in prenatal care. It utilizes high-frequency sound waves to generate detailed, real-time images of the developing babies, their placentas, the umbilical cords, and the surrounding amniotic fluid, all without exposing the mother or the fetuses to ionizing radiation.

At Dr. Essa Lab, the Twin Anomaly Scan is performed using state-of-the-art diagnostic ultrasound systems equipped with advanced imaging technologies such as 3D and 4D rendering, high-resolution color Doppler, and tissue harmonic imaging. These technological capabilities allow consultant radiologists to visualize the intricate structures of the fetal brain, heart, spine, face, and limbs with exceptional clarity. The primary clinical importance of this scan lies in its ability to detect congenital structural anomalies, assess fetal growth patterns, and identify complications unique to multiple gestations, such as Twin-to-Twin Transfusion Syndrome (TTTS) or Selective Fetal Growth Restriction (sFGR). Early detection of these conditions enables obstetricians and fetal medicine specialists to formulate timely management plans, schedule appropriate interventions, and prepare for specialized neonatal care at delivery.

The diagnostic value of a Twin Anomaly Scan is unparalleled in modern obstetrics. It provides a systematic, head-to-toe evaluation of each fetus, ensuring that any subtle deviations from normal development are identified. The scan also confirms chorionicity (the number of placentas) and amnionicity (the number of amniotic sacs) if they were not clearly established during earlier first-trimester scans. Knowing whether twins share a placenta is vital, as monochorionic twins require much closer monitoring due to shared vascular connections. By offering detailed anatomical insights, the Twin Anomaly Scan provides expectant parents with reassurance and equips healthcare providers with the precise clinical data needed to optimize pregnancy outcomes.

Clinical Procedure: What to Expect

Patient Preparation

• Wear comfortable, loose-fitting two-piece clothing to allow easy access to the abdomen during the scan.
• A completely full bladder is generally not required for a mid-trimester scan, but drinking 1 to 2 glasses of water an hour before the test can help optimize visualization.
• No fasting is required; you may eat and drink normally before your appointment.
• Bring all previous ultrasound reports, especially the first-trimester dating or nuchal translucency (NT) scan, to help establish chorionicity.
• Arrive at the diagnostic center 15 minutes prior to your scheduled appointment to complete any necessary registration.

During the Procedure

Upon entering the ultrasound suite at Dr. Essa Lab, the patient will be asked to lie comfortably in a supine position on an examination table. A small amount of warm, water-based gel is applied to the lower abdomen. This gel eliminates air pockets between the skin and the transducer, facilitating the smooth transmission of high-frequency sound waves into the uterus. The consultant radiologist or specialized sonologist will gently move the transducer across the abdomen, applying light pressure to obtain optimal views of both fetuses. Because assessing two fetuses requires double the measurements and a highly detailed evaluation of shared or individual structures, the procedure typically takes between 45 to 60 minutes. The patient may feel mild pressure from the transducer, but the procedure is entirely painless and non-invasive. The radiologist will systematically document the anatomy of Twin A and Twin B, assessing their hearts, brains, spines, limbs, and abdominal organs, while also evaluating the placenta, amniotic fluid levels, and maternal cervical length.

When is a Twin Anomaly Scan Performed?

Assessment of Fetal Development and Anatomy in Multiple Gestations

The primary clinical indication for a Twin Anomaly Scan is the comprehensive assessment of fetal development in multiple gestations. Between 18 and 22 weeks of gestation, the fetal organs have developed sufficiently to be visualized in detail, yet the fetuses are small enough and have enough surrounding amniotic fluid to allow clear imaging from multiple angles. Physicians request this scan to verify that both fetuses are growing symmetrically and that their internal organs, skeletal structures, and facial features are developing normally. This systematic evaluation is crucial for identifying any structural abnormalities that may require specialized medical or surgical intervention immediately after birth.

Identification of Chorionicity-Related Complications

In twin pregnancies, establishing and monitoring chorionicity is paramount. Monochorionic twins (who share a single placenta) are at risk for unique, life-threatening complications due to vascular anastomoses within the placenta. The Twin Anomaly Scan is performed to actively screen for signs of Twin-to-Twin Transfusion Syndrome (TTTS), a condition where blood flows unequally between the babies, and Twin Anemia Polycythemia Sequence (TAPS). By measuring amniotic fluid levels in both sacs and assessing fetal bladder sizes, the scan helps detect these complications early, allowing for timely referral to specialized fetal therapy centers.

Evaluation of Congenital Structural Anomalies

Congenital anomalies are statistically more common in twin pregnancies than in singleton pregnancies. Obstetricians request this scan to meticulously screen for structural defects such as congenital heart disease, neural tube defects, and abdominal wall abnormalities. Because twins can present imaging challenges due to crowding, the expertise of Dr. Essa Lab’s radiologists combined with advanced ultrasound technology is essential to systematically evaluate each fetus’s anatomy, ensuring that even subtle structural anomalies are identified and documented for clinical decision-making.

Monitoring of Amniotic Fluid Volume and Placental Location

The volume of amniotic fluid surrounding each fetus is a key indicator of renal function, placental perfusion, and overall fetal well-being. A Twin Anomaly Scan is performed to measure the deepest vertical pocket of amniotic fluid for each twin. Additionally, the scan precisely localizes the placenta (or placentas) to ensure they are not covering the cervix (placenta previa), which could lead to severe bleeding during pregnancy or delivery. Evaluating the insertion site of the umbilical cord into the placenta is also critical, as abnormal insertions like velamentous or marginal insertions are more common in twins and require careful monitoring.

Assessment of Cervical Length and Preterm Birth Risk

Twin pregnancies carry a significantly elevated risk of preterm labor and delivery. During the Twin Anomaly Scan, the radiologist often performs a transvaginal or transabdominal measurement of the maternal cervical length. A shortened cervix (typically less than 25 mm) in the second trimester is a strong predictor of spontaneous preterm birth. Identifying cervical shortening during this scan allows obstetricians to implement preventive measures, such as cervical cerclage or progesterone therapy, to prolong the pregnancy and improve neonatal outcomes.

What Does a Twin Anomaly Scan Detect?

A Twin Anomaly Scan is highly sensitive and capable of detecting a wide array of structural, chromosomal, and gestational abnormalities. Specifically, this detailed ultrasound examination can identify: 1. Anencephaly (absence of a major portion of the brain and skull). 2. Spina bifida and other open neural tube defects. 3. Hydrocephalus (excessive accumulation of cerebrospinal fluid in the brain). 4. Cleft lip and cleft palate. 5. Congenital heart defects, including ventricular septal defects (VSD) and Tetralogy of Fallot. 6. Diaphragmatic hernia (herniation of abdominal organs into the chest cavity). 7. Duodenal atresia (obstruction of the small intestine). 8. Renal agenesis (absence of one or both kidneys). 9. Infantile polycystic kidney disease. 10. Gastroschisis and omphalocele (abdominal wall defects). 11. Clubfoot (talipes equinovarus) and other limb deformities. 12. Polydactyly (extra fingers or toes) or syndactyly (webbed digits). 13. Skeletal dysplasias (abnormal bone development). 14. Twin-to-Twin Transfusion Syndrome (indicated by discordant amniotic fluid volumes and bladder sizes). 15. Selective Fetal Growth Restriction (significant weight discordance between twins). 16. Single umbilical artery (instead of the normal two arteries and one vein). 17. Placenta previa (placenta covering the internal cervical os). 18. Vasa previa (fetal blood vessels crossing the cervix). 19. Abnormal cervical shortening (increased risk of preterm labor). 20. Oligohydramnios (insufficient amniotic fluid) or polyhydramnios (excessive amniotic fluid) in either sac. 21. Cystic hygroma (lymphatic malformation in the neck). 22. Increased nuchal fold thickness (soft marker for chromosomal abnormalities). 23. Absent or hypoplastic nasal bone. 24. Choroid plexus cysts in the fetal brain. 25. Echogenic bowel (increased brightness of the fetal bowel). 26. Fetal hydrops (abnormal accumulation of fluid in fetal compartments).

Turnaround Time and Report Access at Dr. Essa Lab

At Dr. Essa Lab, we understand that expectant parents and their healthcare providers require prompt and accurate diagnostic results. Following the completion of your Twin Anomaly Scan, the captured ultrasound images and measurements are meticulously analyzed by our consultant radiologists. A comprehensive, detailed diagnostic report is typically compiled and verified within a few hours of the procedure. Patients can conveniently access and download their reports online through the secure Dr. Essa Lab patient portal or mobile application. Additionally, physical copies of the report, complete with high-resolution printed ultrasound images, can be collected directly from the diagnostic center. Our streamlined reporting process ensures that your obstetrician receives the vital clinical information necessary to guide your prenatal care without unnecessary delay.

Twin Anomaly Scan Findings Overview

Structure / Parameter Evaluated	Normal Findings	Possible Abnormal Findings
Fetal Brain & Skull	Intact cranium, normal ventricles, visible cerebellum and cisterna magna.	Anencephaly, ventriculomegaly, hydrocephalus, lemon or banana sign.
Fetal Spine	Regular alignment of vertebrae, intact overlying skin.	Spina bifida, hemivertebrae, sacral agenesis.
Fetal Heart	Four-chamber view, normal outflow tracts, regular rhythm (120-160 bpm).	Ventricular septal defect, hypoplastic left heart, transposition of great arteries.
Fetal Face	Intact upper lip, presence of nasal bone, normal orbits.	Cleft lip, cleft palate, micrognathia, orbital hypertelorism.
Fetal Limbs	Three segments present in all four limbs, normal hand and foot positioning.	Clubfoot, polydactyly, skeletal dysplasia, limb shortening.
Placenta & Membranes	Clear separation of amniotic sacs, normal placental position away from cervix.	Placenta previa, shared placenta with vascular anastomoses (monochorionic).
Amniotic Fluid Volume	Normal deepest vertical pocket (2-8 cm) in each gestational sac.	Oligohydramnios (less than 2 cm), polyhydramnios (greater than 8 cm).
Cervical Length	Cervix closed and measuring greater than 25 mm.	Shortened cervix (less than 25 mm), cervical funneling.

Note: Diagnostic findings should always be interpreted by a qualified healthcare professional together with the patient’s symptoms, medical history, physical examination, laboratory investigations, previous imaging studies, and other relevant clinical information. Additional investigations or specialist consultation may be recommended depending on the findings.

Why Choose Dr. Essa Lab for Twin Anomaly Scan?

• Experienced consultant radiologists specializing in high-risk obstetric and fetal imaging.
• Advanced high-resolution ultrasound machines with 3D/4D capabilities for superior anatomical detail.
• Strict adherence to international diagnostic protocols for multiple gestations and fetal anomaly screening.
• Comprehensive patient-focused care in a comfortable, private, and professional environment.
• Convenient online report access and digital image downloading through a secure patient portal.
• A trusted network of diagnostic centers across Karachi with a legacy of excellence since 1987.
• Accurate, detailed, and timely reporting to facilitate prompt clinical decision-making.
• Dedicated support staff to assist expectant mothers throughout their diagnostic journey.