Can stress kill your unborn child?

This article first appeared in the April/May 2016 issue of Your Pregnancy magazine. 

Pregnancy is stressful. You’re growing the little person who’ll have the most profound effect on your life ever. The stakes couldn’t be higher.

So a certain amount of anxiety is only to be expected – and can even work in your favour. After all, knowing how important it is will motivate you to make responsible choices about your health, fitness, diet and work-life balance. 

But bad stress has been shown to increase the risk of preterm delivery, and is a contributing factor in low birth weight babies. It could even affect your baby’s personality and academic performance in the future. 

• Also see: Obsessive-compulsive and pregnant 

Stress can cause labour 

When you’re stressed, your white blood cell count can decrease. These cells fight off infection. Pregnant women’s immune systems are already less strong (your body cleverly weakens its infection fighters to reduce the risk of the body rejecting the growing baby as an alien invader). If the foetus gets an infection in the womb – a medical emergency – your stress really could make your baby very sick indeed. 

A study in Toronto on rats found that “stress across generations becomes powerful enough to shorten pregnancy length in rats,” says Dr Gerlinde Metz in the journal BMC Medicine. The effect became more and more noticeable with each new generation of stressed mothers. The researchers speculated that elevated stress in humans over years could also lead to more preterm births.  

When we’re stressed, our bodies secrete the corticotropin-releasing hormone (CRH). But CRH also regulates how long a pregnancy lasts, and it does this so accurately it’s actually called the “placental clock”. Levels of CRH rise in the third trimester to stimulate contractions, and reading your CRH levels at 16 to 20 weeks can predict your delivery date.

A 1999 study in the American Journal of Obstetrics and Gynecology, as well as other studies, found that women who had premature births also had very high levels of CRH in their systems, and additionally reported feeling very stressed.

Those with the lowest levels of CRH delivered latest. What this means is that CRH, which is present when you’re stressed, can cause preterm births – and stress in the first trimester was the most dangerous of all.

• Also see: What worries South African moms?  

Cortisol, a stress hormone   

CRH stimulates the production of cortisol – another stress hormone. In 2011 the Journal of Child Psychology and Psychiatry published a study in which cortisol levels in mothers and babies were measured – and found that the levels were similar. The more highly stressed babies were also more upset at having their blood drawn.

The problem is that synthetic cortisol is given to pregnant women who are at risk of going into early labour to mature the baby’s lungs and give a preemie the best fighting chance “on the outside”.

And this study confirmed that children who were given cortisol in the womb have a thinner rostal anterior cingulated – an area of the brain that manages emotional regulation. The children were judged as “more anxious” than others.

Stressed environment, stressed baby 

Dr Pathik Wadhwa at the University of California at Irvine, quoted on Medicine.net, says a foetus develops in part in response to its environment.

A foetus in a high-stress environment is at risk of a range of stress-related problems. “Developmental psychologists once thought foetuses were conceived with a ‘blueprint’ from their parents’ genes.

As long as you gave the growing foetus the right nutrients and avoided harmful substances, this blueprint would develop into a healthy baby,” says Dr Wadhwa. “This view has been more or less completely turned upside down.” Dr Wadhwa says that the foetus responds to cues from his or her environment all the time to decide how to develop, “within the parameters of its genes”.

Some studies have suggested that stress can even affect a baby’s temperament and intelligence. First trimester stress in the mother was linked to more depressed or irritable children, and they were less able to “habituate” in the womb (this is the ability to tune out unimportant stimuli and it predicts IQ).

• Also see: Antenatal depression: When your bump brings the blues  

A baby's brain can repel stress 

Recently Professor Jonathan Seckl, an endocrinologist at the University of Edinburgh, discovered that an enzyme in the placenta and in a baby’s brain actually deactivates cortisol. “It seems to be a natural barrier to stress hormones,” he says. “If you inhibit this barrier then you start to get children being born with low birth weight and who have altered stress responses and depression.” 

If the enzyme is stopped, stress hormones can cross into the baby’s brain. As a result, depression, anxiety and ADHD could be much more common in children exposed to cortisol.

And what inhibits this barrier? Well, very high levels of stress in the mother can overwhelm the barrier, while other individuals are simply born with lower levels of the enzyme. So the jury is out on whether you can actually be “creating” a stressed baby – but it’s possible. 

Chronic stress is the worst 

Dr Christine Dunkel-Schetter, a psychology professor at UCLA, is currently studying the types of stress that are most harmful in pregnancy and her initial findings are that constant anxiety, for instance fear and worry about the pregnancy, is more damaging than stressful life events such as trauma or death. 

Chronic stress is horrible, causing headaches, muscle tension, sleep disturbance, mood disturbance, digestive issues, high blood pressure... and that’s just for the mother!

It’s in both your and your baby’s interests that you find ways to distress.

• Also see: What is foetal distress and the non-stress test? 

Stress busters

1. Dr Wadwha at the University of California at Irvine says that a good support network is great for managing your stress levels. Reach out to your partner, family and friends. 
2. Good information about pregnancy and prenatal care is a stress antidote, says Dr Wadwha. Arm yourself with information, so you don’t need to be stressed out by speculation and old wives’ tales. Well done for reading this – you’ve already made a good start!
3. Be good to your body by sticking to a good, healthy diet. Scientists know that the connection between the gut and our emotions is direct.
4. Exercise has proven stress-killing properties: it releases endorphins and makes you feel good. So add pregnancy-safe exercise to your day, such as walking or swimming, yoga or Pilates. Meditation or a period of quiet reflection each day is the cherry on top! 
5. Dr Wadwha says that having a sense of control, good self-esteem and optimism are great for combating stress. If you’re struggling here, investigate whether you could access professional help from a psychologist, counsellor, priest or healer. Try the South African Depression and Anxiety Group on sadag.org or Famsa’s national office on 011 975 7106 for a list of resources in your area – many are free of charge. 

Do you have a question about your pregnancy health that you'd like an expert's feedback on? Email to and we may publish your question along with advice from a specialist.

Please note that we cannot supply personalised advice.

Read more: 

• Mom's stress affects baby 
• Sleep well while pregnant  
• Plump enough for pregnancy?  

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Can you miscarry a baby from stress?