# Fetal Alcohol Syndrome and Teratogens

> Fetal alcohol syndrome and teratogens for NEET-PG Paediatrics cover the facial dysmorphism of FAS and the classic drugs with their effects on the fetus.

- Canonical URL: https://prepelephant.com/topics/neet-pg/paediatrics/fetal-alcohol-syndrome-and-teratogens
- Exam / course: NEET-PG · Subject: Paediatrics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Nelson Textbook of Pediatrics; Smith's Recognizable Patterns of Human Malformation
- How to cite: "Fetal Alcohol Syndrome and Teratogens", PrepElephant, https://prepelephant.com/topics/neet-pg/paediatrics/fetal-alcohol-syndrome-and-teratogens

## Direct answer

Fetal alcohol syndrome is the most severe end of the fetal alcohol spectrum, caused by prenatal alcohol exposure and marked by growth restriction, central nervous system dysfunction and a characteristic face with short palpebral fissures, a smooth philtrum and a thin upper lip. No safe level of alcohol in pregnancy has been established. Teratogens act in organ-specific windows, so the timing of exposure determines which system is harmed.

## What you must remember

- **Growth:** prenatal and postnatal growth restriction is common, with low birth weight.
- **Face:** short palpebral fissures, smooth philtrum, thin vermilion border of the upper lip and a flattened midface.
- **Brain:** microcephaly, intellectual disability and behavioural or attention problems.
- **Spectrum:** alcohol-related neurodevelopmental disorder causes brain involvement without the full facial pattern.
- **Diagnosis:** requires reliable evidence of prenatal exposure plus facial, growth and central nervous system features.
- **Critical window:** neural tube closure occurs in the first month after conception, and organogenesis runs through the first trimester.
- **Valproate:** neural tube defects, reduced cognitive outcome and autism spectrum disorder in exposed children.
- **Thalidomide:** the classic historical teratogen, causing limb reduction defects.

## Classic teratogens and their fetal effects

Teratogen questions test both the agent and the timing of exposure. The table lists classic agents with the fetal effect an examiner expects.

| Agent | Fetal effect | Exam point |
| --- | --- | --- |
| Alcohol | Fetal alcohol spectrum, growth restriction, intellectual disability | No safe level |
| Isotretinoin | Craniofacial, cardiac outflow and CNS defects | Exclude pregnancy and ensure contraception |
| Valproate | Neural tube defects, reduced IQ, autism spectrum | Avoid in women of reproductive age unless no alternative |
| Warfarin | Nasal hypoplasia, stippled epiphyses, CNS anomalies | Heparin preferred in early pregnancy |
| ACE inhibitors | Oligohydramnios, renal dysplasia, skull hypoplasia | Harmful in second and third trimesters |
| Tetracyclines | Dental enamel discolouration, impaired bone growth | Avoid in pregnancy and young children |

Warfarin harms the fetus mainly in early pregnancy, while ACE inhibitors cause renal and skull effects later on. The same drug can produce a different defect depending on the trimester.

Counselling before prescribing is therefore the real preventive step. A woman of reproductive age on a teratogenic drug needs a documented plan for pregnancy testing and contraception.

## Where the exam tries to catch you

Teratogen questions reward the drug, the trimester and the fetal defect read together.

- **Trap:** assuming a light drinking pattern in pregnancy is harmless. — **Correct:** no safe level is established, so abstinence is advised throughout pregnancy.
- **Trap:** linking valproate only with spina bifida. — **Correct:** it also reduces cognitive outcome and raises autism spectrum risk, so it is avoided in women of reproductive potential unless alternatives fail.
- **Trap:** recommending warfarin for a pregnant woman with a mechanical valve without weighing the embryopathy risk. — **Correct:** heparin is usually preferred in early pregnancy, with warfarin used only after specialist review.
- **Trap:** insisting that facial features are needed to suspect alcohol damage. — **Correct:** alcohol-related neurodevelopmental disorder causes brain involvement without the full facial pattern.

## Frequently asked questions

### What are the facial features of fetal alcohol syndrome?

The classic facial features of fetal alcohol syndrome are short palpebral fissures, a smooth philtrum and a thin upper vermilion border. A flattened midface and epicanthal folds may also be seen. These features support the diagnosis but are not present in every affected child.

### Is there a safe amount of alcohol in pregnancy?

No safe amount of alcohol in pregnancy has been established, so current guidance advises complete abstinence. The harm depends on dose and timing, and the fetal alcohol spectrum can follow varying levels of exposure. Avoidance before pregnancy is recognised, since many pregnancies are unplanned.

### Which antiepileptic drug causes neural tube defects in the fetus?

Valproate is the antiepileptic drug best known for causing neural tube defects such as spina bifida. It is also linked with reduced cognitive outcome and autism spectrum disorder in exposed children. For women of reproductive age, alternatives are preferred where clinically reasonable.

### Which anticoagulant causes nasal hypoplasia and stippled epiphyses in the fetus?

Warfarin causes the warfarin embryopathy, with nasal hypoplasia and stippled epiphyses, when exposure occurs in early pregnancy. CNS anomalies and growth restriction may also follow. Heparin is therefore the usual anticoagulant in early pregnancy.

### Which teratogen causes ear, cardiac and craniofacial defects?

Isotretinoin, a retinoic acid derivative, causes a pattern of ear, cardiac outflow, craniofacial and CNS defects when taken in pregnancy. Pregnancy must be excluded before therapy and contraception ensured throughout treatment. The pattern is a reminder that teratogens must be counselled before use.