கர்ப்ப கால ஸ்கேன்
Growth Scan (Third Trimester Ultrasound)
Checks your baby's size, growth, and wellbeing in the third trimester
இது என்ன ஸ்கேன்?
A growth scan is a third trimester ultrasound (typically from 28 weeks onwards) that measures your baby's size and estimates fetal weight. The sonographer measures four key parameters: Biparietal Diameter (BPD — head width), Head Circumference (HC), Abdominal Circumference (AC — the most sensitive indicator of nutrition), and Femur Length (FL — thigh bone length). These measurements are entered into a formula to calculate the Estimated Fetal Weight (EFW). Amniotic fluid volume and placental position are also assessed.
இது ஏன் செய்யப்படுகிறது?
Growth scans are done to check that your baby is growing at the expected rate along the growth curve for their gestational age. A baby growing well is reassuring. A baby growing too slowly (Small for Gestational Age or Fetal Growth Restriction) may indicate placental insufficiency — the placenta is not delivering enough nutrition and oxygen. A baby growing too large (Large for Gestational Age) may be seen in gestational diabetes. Serial growth scans (repeating every 2–4 weeks) are more informative than a single scan, as they track the trajectory of growth.
என்ன எதிர்பார்க்கலாம்
A growth scan is similar to other abdominal ultrasounds — gel on the belly, probe moved to measure the baby from different angles. It typically takes 20–30 minutes. The sonographer will also assess amniotic fluid (either as Amniotic Fluid Index/AFI or Single Deepest Pocket/SDP) and may include a Doppler assessment of blood flow if indicated. Results are plotted on a growth chart by your doctor to see whether measurements are tracking on a consistent percentile.
சாதாரண முடிவுகள்
- ✓ EFW (Estimated Fetal Weight) between the 10th and 90th percentile for gestational age
- ✓ Abdominal circumference (AC) on the expected growth curve
- ✓ AFI (Amniotic Fluid Index) 8–24cm, OR Single Deepest Pocket (SDP) 2–8cm
- ✓ Fetal growth velocity consistent — not dropping across percentiles between scans
- ✓ Placental position and maturity appropriate for gestation
எப்போது கவலைப்பட வேண்டும்
- EFW below the 10th percentile — Small for Gestational Age (SGA); may need Doppler assessment
- EFW below the 3rd percentile — Severe FGR (Fetal Growth Restriction); close monitoring required
- EFW above the 90th percentile — Large for Gestational Age (LGA); seen in uncontrolled GDM
- Growth velocity dropping — crossing two or more percentile lines downward between scans
- Oligohydramnios (AFI < 5cm or SDP < 2cm) — reduced fluid is a sign of fetal compromise
- Polyhydramnios (AFI > 24cm) — associated with GDM or fetal swallowing problems
அடிக்கடி கேட்கப்படும் கேள்விகள்
How accurate is the estimated fetal weight from a growth scan?
The EFW from ultrasound has an error margin of approximately ±10–15% — so a baby estimated at 2.5kg could weigh anywhere between 2.1kg and 2.9kg at birth. This variability is inherent to the method. EFW is most useful for identifying trends over serial scans rather than as a single definitive measurement.
My baby is on the 20th percentile — is that normal?
Yes. Percentile simply means where your baby ranks among 100 babies of the same gestational age. The 20th percentile means 80 out of 100 babies are larger. Being on any percentile between 10 and 90 is considered normal, and what matters is that your baby stays on a consistent percentile across multiple scans — not that they are on a higher one.
What is the difference between SGA and FGR?
SGA (Small for Gestational Age) simply means the baby measures below the 10th percentile — they may be constitutionally small (healthy, just small parents) with no cause for concern. FGR (Fetal Growth Restriction) means the baby is failing to reach its growth potential because of a problem — usually placental insufficiency. FGR is diagnosed when growth is poor AND Doppler blood flow shows abnormalities. Not all SGA babies have FGR.
How often will I need growth scans?
For a low-risk pregnancy, a single growth scan at 28–32 weeks is often sufficient. For higher-risk pregnancies (twins, GDM, hypertension, previous SGA baby, reduced movements), growth scans are done every 2–4 weeks from 28 weeks, sometimes more frequently. Your doctor decides the schedule based on your specific situation.
Does a large baby always mean I will need a C-section?
Not necessarily. EFW estimates have significant margins of error. Many 'large on scan' babies deliver vaginally without difficulty. Your doctor considers multiple factors — actual EFW, your pelvis, diabetes control, baby's position, and clinical examination — before making any delivery planning decisions. A single large EFW estimate alone is rarely the sole reason for a C-section.