Teratogens – The first threat your baby will face

What are teratogens? Teratogens are agents that can cause abnormalities in a developing foetus (ref). They can act directly on the foetus or indirectly through maternal structures such as the placenta (ref). These agents can have varying effects on the foetus such as mild or severe abnormalities and some can even cause death. The age of the foetus at time of exposure is critical in what the consequence of exposure may be. Teratogens come in many forms and cover more than just the potential threat of some medications during pregnancy.

When is your baby vulnerable? The foetus is vulnerable throughout the entire pregnancy, however there are periods where there is more risk than others. The first trimester, particularly week two to eight are when the foetus is most vulnerable to teratogens because this is when the baby’s organs are developing (ref). This is not to say that the foetus is unaffected later on in pregnancy. Ibuprofen for example has been shown to cause adverse effects to the foetus’s cardiovascular development when taken after 34 weeks (ref).

What to look out for! There are three main categories of teratogens:

Physical

Chemical

Disease

o Ionising radiation o Temperature o Mercury o Lead

o Illicit drugs: o Cocaine o Heroine

o Warfarin o Alcohol o Cigarette Smoke

o Rubella o Diabetes o Epilepsy o Cytomegalovirus

Teratogens – The first threat your baby will face

Chemical - Alcohol and medications are the most common teratogenic agents. Certain medications and all illicit drugs can be extremely dangerous to a developing foetus as these can pass through the placenta (ref). There, it is very important to notify any prescribing doctor that you are pregnant and to always start any medication with caution (ref paper). In the final stages of development, the only teratogen agents that will harm the baby are ones that interfere with the supply of nutrients, hormones or oxygen (ref paper). Medications can fall into this category as they pass through the placenta and impact these supplies. Environmental – Radiation is the most commonly known threat to a developing foetus as it can cause cell death and genetic mutations (ref). Therefore, any imaging scans that use radiation should only be done in an emergency situation. Roughly 10-15% of congenital structural abnormalities are as a result of environmental factors during foetal development (ref paper). Disease – Rubella is capable of producing a large array of different defects in a developing foetus many of which are fatal (52 – ref paper). The age of the foetus predicts what impact rubella will have on development however, If the foetus survives it is likely to be born with congenital rubella syndrome as well as other possible abnormalities (53). The most effective way to reduce the risk of rubella abnormalities on a foetus is for the mother to be immunised (ref – paper). Diabetes is also a very common teratogen as insulin is known to have adverse reactions on the foetus causing many congenital malformations which can result in death (ref paper).

Mutagens VS Teratogens Mutagens and teratogens are very similar as they both cause abnormalities. The difference however is that mutagens change the genetic information of an embryo while teratogens impact a developing foetus (ref). Therefore, mutagens are something that unfortunately a mother has no control over while most teratogens can be avoided during pregnancy and significantly reduce the risk to the foetus.