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Why Are Some Birth Defects Only Detected After Delivery?
Prenatal scans are wonderful as they give you a first look at your baby and how they are developing. But they do have their limits. Ultrasounds show the structure of your baby, like the heart, brain, and other organs.Genetic tests can detect certain chromosome problems. Yet, many conditions affect how an organ works rather than how it looks, and these cannot always be seen on a scan.
Some issues also develop slowly or only become noticeable once your baby starts using that part of their body after birth. This is why, even with the best care and the most advanced scans, some conditions are usually diagnosed only when your little one arrives.
Which Congenital Conditions Are Often Undetected Before Birth?
These are the main groups of conditions that routine prenatal tests often miss:- Degenerative disorders: These are progressive conditions that get worse as the child grows. At birth, everything may look perfectly normal because the effects haven’t started yet. Examples include Rett syndrome and muscular dystrophy.
- Sensory conditions: Problems with hearing or vision often go unnoticed in the womb because the baby isn’t using those senses the same way yet. Conditions such as complete blindness, hearing loss, or deafness usually become clear only after birth, when newborn hearing screening is done or when parents notice the baby isn’t responding to sounds or light.
- Metabolic disorders: These happen when the body cannot process certain substances properly because of missing or faulty enzymes. Common examples are hypothyroidism, phenylketonuria (PKU), and Tay-Sachs disease. They don’t change the baby’s appearance on ultrasound, so they're usually detected through newborn blood tests done in the first few days of life.
- Certain structural heart defects: Many heart problems can be seen on detailed scans, but some milder or specific defects may be missed. These are often discovered during the newborn check-up or later follow-ups.
How Are Undetected Congenital Conditions Found After Delivery?
Every newborn goes through some important checks right after birth to make sure they’re healthy:- Physical examination: A paediatrician checks your baby from head to toe for any visible signs of issues.
- Newborn screening: Often called the heel-prick test, this uses just a few drops of blood to check for metabolic and other disorders.
- Hearing screening: Simple and painless tests done within the first month help spot any hearing problems early.
- Additional tests: Sometimes, if a baby shows feeding difficulties, unusual sleepiness, or other signs in the first few weeks, further tests may be recommended.
What Causes Congenital Conditions?
In most cases, there’s nothing you did or didn’t do that caused the condition. Some common reasons include:- Genetic changes passed down from family.
- Random chromosome differences that happen during early development.
- Exposure to certain infections, medicines, or substances during pregnancy
- A mix of factors, often both genetic and environmental.
- Taking folic acid before and during early pregnancy.
- Avoiding alcohol and smoking.
- Managing conditions like diabetes.
- Keeping up with all your antenatal visits.
What Does Research Say About Limitations of Antenatal Ultrasound
A detailed 2025 study looked at why antenatal ultrasounds sometimes miss congenital anomalies, with a focus on challenges in India. It found that even in top medical setups, ultrasounds detect only 50 to 70 per cent of major issues, and the rate is often lower in everyday practice.Common missed problems include:
- Complex heart defects like transposition of the great arteries (TGA)
- Hypospadias in males
- Isolated cleft palate
- Gastrointestinal blockages such as oesophageal atresia
- Limb issues like partial deletions or fused fingers
- Skeletal conditions like achondroplasia
Living with a Congenital Condition
If your baby is diagnosed with a congenital condition after birth, the first few days can feel overwhelming. Some children may only need simple treatment or regular check-ups, while others might need extra support through childhood. Paediatric specialists, physiotherapists, and early intervention teams work together to create a care plan tailored to your child.It’s important to remember that many children with these conditions grow up happy, achieve their dreams, and lead full lives. You can talk to families who’ve been through similar experiences to make things feel a lot less scary.
Keep in mind that no test can guarantee a perfectly healthy baby, but the checks we have today catch most problems either before birth or soon after.
No test can catch every possible birth defect. While ultrasounds and genetic screenings detect many major issues, some conditions only become clear after birth. But if you ever feel worried, speak to your gynaecologist or paediatrician openly.
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FAQs on Birth Defects That Often Go Undetected During Pregnancy
- Can down syndrome be detected during pregnancy?
Yes. Down syndrome can often be detected through a combination of prenatal screening tests and diagnostic tests like amniocentesis or chorionic villus sampling, though no test is 100 per cent accurate. - Can genetic tests detect every disorder?
No, genetic tests screen for common chromosomal abnormalities and some gene disorders. But rare or complex genetic conditions may not be detected.