A growth scan answers a simple question: is the baby growing as expected? Measurements of the head, abdomen and thigh bone are used to estimate the baby’s weight, which is plotted on a growth chart so that the pattern over several scans can be seen, not just one number.
A Doppler scan adds information about blood flow. By looking at the umbilical cord, an artery in the baby’s brain and, where needed, a vein near the heart, it shows how well the placenta is supplying the baby. When a baby is small, Doppler helps tell a healthy small baby apart from one whose placenta is struggling, and that distinction guides how often to scan and when birth is safer than staying in the womb.
Dr. Devang Patel holds the FNB fellowship in High Risk Pregnancy & Perinatology, and growth and Doppler surveillance is a routine part of high-risk pregnancy care at Divine Women’s Hospital, Gota. The consultant who performs the scan is the one who decides the plan, with 24×7 labour care and neonatal support on site.
What is measured
- Head circumference, abdominal circumference and femur length, giving an estimated fetal weight (EFW)
- The baby’s centile on a growth chart, and the trend since the last scan
- Amniotic fluid, as the deepest vertical pool (normal about 2–8 cm) or the amniotic fluid index
- Umbilical artery Doppler: resistance to flow in the placenta
- Middle cerebral artery (MCA) Doppler and the cerebroplacental ratio (CPR)
- Ductus venosus Doppler in early, severe growth restriction
- Uterine artery Doppler: blood supply on the mother’s side of the placenta
- Placenta position and the baby’s presentation in the third trimester
Small for dates or growth restriction?
Babies whose estimated weight is below the 10th centile are called small for gestational age (SGA). Many are healthy and simply small, often like their parents. Fetal growth restriction (FGR) is different: the baby is not reaching its growth potential, usually because the placenta is not working well.
Following the international Delphi consensus, FGR is diagnosed when the baby is below the 3rd centile, or when a small baby also shows abnormal Doppler, or when growth falls across centiles between scans. FGR affects roughly 5 to 10% of pregnancies and is one of the commonest causes of stillbirth that can be anticipated. Early-onset FGR (before 32 weeks) is usually more severe and shows clear Doppler changes; late-onset FGR (after 32 weeks) is more common, milder on Doppler and easier to miss.
Who is at higher risk of growth problems
- High blood pressure or pre-eclampsia, now or in a previous pregnancy
- Pre-existing diabetes with vascular disease, kidney disease, lupus or APLA
- A previous baby who was small or stillborn
- Smoking or tobacco chewing, including gutka and mishri
- Moderate to severe anaemia or very low body weight before pregnancy
- Twins, especially monochorionic twins sharing one placenta
- Age over 40, or low PAPP-A or abnormal uterine artery Doppler in early pregnancy
Understanding the Doppler results
Each vessel tells a different part of the story. Reading them together shows how far the placenta is struggling and how the baby is coping.
| Vessel | What it shows | What an abnormal result usually means |
|---|---|---|
| Umbilical artery | Resistance in the placenta | Raised PI: closer monitoring; absent or reversed flow: delivery is planned, often early |
| Middle cerebral artery | Blood flow to the brain | Low PI suggests the baby is protecting the brain (brain-sparing) |
| Cerebroplacental ratio | MCA PI divided by umbilical PI | Low CPR is an early sign of late FGR, even when umbilical flow is normal |
| Ductus venosus | Heart function and venous pressure | Absent or reversed a-wave in early FGR means delivery is needed soon |
| Uterine arteries | Mother’s supply to the placenta | Raised resistance points to placental problems and pre-eclampsia risk |
How the results guide monitoring and timing of birth
When growth and Doppler are normal, routine care continues. When a baby is SGA with normal Doppler, growth is usually rechecked every two weeks with Doppler in between, and birth is often planned at 37 to 38 weeks.
When the umbilical artery Doppler is abnormal, scans become more frequent, sometimes twice a week, combined with CTG monitoring of the baby’s heart rate. With absent end-diastolic flow, birth is usually planned by about 34 weeks; with reversed flow, by about 30 to 32 weeks, or earlier if the ductus venosus or CTG worsens.
If birth before 34 weeks is likely, steroid injections are given to mature the baby’s lungs, and magnesium sulphate before 32 weeks helps protect the brain. The neonatal team meets you in advance.
For a baby who is small but otherwise well, the commonest plan is induction of labour at 37 to 38 weeks with continuous CTG in labour, because growth-restricted babies have less reserve during contractions.
The aim of every growth scan is to time birth well: not too early, and not too late.
Growth scans in other situations
Growth scans are used when the baby seems large, as in gestational diabetes, where an abdominal circumference above the 95th centile may lead to tighter sugar control. They check fluid when there is too much (polyhydramnios) or too little (oligohydramnios), compare the babies in twins, and assess the baby when your fundal height measures more than 2 cm away from your weeks.
In Indian women, using a chart suited to the population avoids labelling too many healthy babies as small. Charts such as INTERGROWTH-21st, based on multi-ethnic data including India, are commonly used.
Diet still matters for the mother. A plate with dal, paneer, curd, eggs or pulses for protein, green leafy vegetables and iron-rich foods such as ragi, jaggery in moderation and dates, plus prescribed iron and calcium, keeps anaemia in check and supports the placenta, even though it cannot reverse established FGR.
Effect on future pregnancies
After a pregnancy with FGR or early pre-eclampsia, the chance of it happening again is raised. In the next pregnancy, first-trimester screening, low-dose aspirin from 12 weeks where indicated, and earlier growth scans from about 24 to 28 weeks are usually advised.
Placental problems are also an early signal for heart health later in life, so blood pressure, weight and sugar checks every few years are sensible for the mother.
How surveillance is organised at Divine Women’s Hospital
Growth and Doppler scans are performed by Dr. Devang Patel and reviewed against all your earlier scans on one chart, so small changes in trend are not missed. When Doppler is abnormal, CTG monitoring can be done on the same visit, and blood pressure, urine and blood tests are added if pre-eclampsia is a concern.
Between scans, you are asked to keep track of your baby’s movements from about 28 weeks. There is no magic number of kicks: what matters is your baby’s usual pattern. Any reduction is a reason to come in the same day, at any hour, because the hospital provides 24×7 labour and emergency care.
If early birth becomes likely, you meet the neonatal team beforehand, steroid and magnesium sulphate plans are made, and the timing and mode of birth are agreed with you and your family rather than decided in a rush.
A note on the PCPNDT Act
Pre-natal sex determination is prohibited in India under the PCPNDT Act. The sex of the baby is not detected or disclosed at any scan.
Your care, step by step
- MeasurementsHead, abdomen and femur are measured and the estimated weight is plotted on your personal growth chart.
- Fluid and placentaAmniotic fluid volume, placental position and the baby’s presentation are checked.
- Doppler studiesBlood flow in the umbilical, brain and, where needed, uterine and venous vessels is recorded.
- InterpretationResults are compared with the previous scans and explained, with CTG added where needed.
- Interval planYou leave knowing when the next scan is due, which warning signs to report, and the likely plan for birth.
When to book a visit
- Your bump measures smaller or larger than expected for your dates
- You have high blood pressure, pre-eclampsia, diabetes, kidney disease or APLA
- A previous baby was small, stillborn or born early because of growth problems
- An earlier scan showed low fluid, a small baby or abnormal Doppler
- You are carrying twins
- Your PAPP-A was low or uterine artery Doppler was abnormal at the NT scan
Warning signs - get same-day care
- Your baby is moving less, or the pattern of movement has changed
- Severe headache, blurred vision, or pain under the ribs on the right
- Vaginal bleeding, especially with abdominal pain or a hard, tender uterus
- Leaking fluid from the vagina
- Regular painful tightenings before 37 weeks
- Sudden swelling of the face, hands or feet
Labour and emergency care are available 24 × 7. Call the hospital and come in directly.
Myths and facts
Myth: Eating more, ghee or dry fruits will make a small baby grow.
A balanced diet matters, but extra calories do not correct growth restriction caused by the placenta. They mainly increase the mother’s weight.
Myth: A small baby will have an easier normal delivery.
Growth-restricted babies tolerate labour less well and need closer monitoring. The plan depends on the Doppler and CTG, not the size alone.
Myth: A big estimated weight always means a caesarean.
Scan weights can be out by 10–15%. The decision considers the whole picture, including diabetes, previous births and the baby’s position.
Myth: Doppler scans are harmful to the baby.
Doppler uses ultrasound within standard safety settings and is kept as short as needed. Its benefit in high-risk pregnancy is well established.
Frequently asked questions
What is a normal umbilical artery Doppler result?
Blood keeps flowing forward through the umbilical artery throughout the heartbeat, and the pulsatility index falls steadily as pregnancy advances. Results are compared with charts for the exact week. Raised resistance, or flow that stops or reverses, needs closer monitoring.
How accurate is the estimated baby weight on scan?
Usually within about 10 to 15% of the actual birth weight. That is why the trend over several scans matters more than any single estimate.
Why is my baby measuring small?
Sometimes the dates are slightly out, sometimes the baby is constitutionally small like its parents, and sometimes the placenta is not supplying enough. Doppler and repeat measurements help tell these apart.
How often are growth scans needed?
Growth is not usually re-measured more often than every two weeks, because shorter gaps make real growth hard to judge. Doppler may be checked more often, even twice a week, when the placenta is under strain.
What does brain-sparing mean on a Doppler report?
It means the baby is redirecting blood towards the brain because the placenta is not supplying enough oxygen. It is a sign to monitor more closely and plan timing of birth.
What is a normal amniotic fluid level?
A deepest pool of about 2 to 8 cm, or an AFI of about 5 to 24 cm, is normal in the third trimester. Low fluid may be linked to placental problems or leaking; high fluid to diabetes or, rarely, a baby’s condition.
Will I need a caesarean if my baby has FGR?
Not necessarily. Many babies with late FGR and stable Doppler can be induced and born vaginally with continuous monitoring. With severe Doppler changes, a caesarean is often safer.
Does low-dose aspirin help a small baby?
Aspirin started before 16 weeks reduces the chance of pre-eclampsia and some early FGR in high-risk women. Starting it after FGR is found does not reverse it.
What should I do if my baby is moving less?
Do not wait for your next scan. Contact the hospital the same day; a CTG and scan can be done straight away.
Does bed rest help a growth-restricted baby?
No. Strict bed rest has not been shown to improve growth and raises the risk of blood clots. Normal light activity, good sleep on your side in the third trimester and attending planned scans are what help.