Do high stress moments affect a fetus?

Question

Recently my wife was driving and nearly hit a person who pulled out in front of her, and noticed a strong clenching in her stomach.

There are quite a few websites indicating that a high-stress lifestyle affects the fetus, but I'm more interested in:

1. Whether the baby can feel the stress of such moments (not including external physical events, such as braking)
2. Whether such moments have any kind of long-lasting effect on the baby.

I am unable to find any studies indicating the above, but I'm looking for a more fact-based answer than opinion. Thank you!

Answer 1

No doubt, if your wife was jostled, the baby felt this. More than that is hard to say.

As women have been having healthy babies in spite of acute stressors of all kinds, I'd imagine that one episode has no lasting effect on the fetus.

When your wife feels fear (for example, a near accident), her body releases stress hormones, such as epinephrine and cortisol. Epinephrine causes an elevated heart rate, increases respiratory rate, trembling, etc. In high doses (e.g. those given for anaphylactic shock), this can lead to symptoms of fetal distress, however it's thought to be caused by the effect of epinephrine on the placenta more than on the fetus (epinephrine causes a decreased placental blood flow.)

The baby's heart rate and movements respond to many things, even blood sugar. A fetal non-stress test relies on this information to evaluate the general health of the baby when there is any doubt.

In physiological doses (such as the amount released by the adrenal glands on your wife's near miss accident), I would not be surprised at all if the baby's heart rate would increase as well, but not nearly as dramatically as your wife's did. It's estimated that only 10-12% of maternal epinephrine reaches the fetus. Your wife has a much stronger response.

The placenta actually 'deactivates' cortisol, decreasing it's effects. A one-time stressor - again - is both common and not easy to study: 9 months is a long time; how would one know what outcome was caused by a particular event?

It is known, however, that prolonged, significant exposure to cortisol might adversely affect a fetus.

Answer 2

I think @anongoodnurse provided a fine answer. For your first question, I can't find anything on whether or not a fetus feels the stress of a moment. But I did find this article about how stress can affect a pregnancy in general.

1. Preterm labor and premature birth
2. Miscarriage
3. Low birth weight
4. Risk of infection
5. Increased problems later in life

The end of the article states:

links between stress and pregnancy are still being formed, and only the most extreme stressful situations are likely to cause problems.

But it would appear that a low-stress pregnancy would be ideal :)

Answer 3

(returning late to the party)

In my reading I just came across this impressive paper regarding maternal stress:

"Stress during Pregnancy and Offspring Pediatric Disease: A National Cohort Study"

Description: "The purpose of this study was to assess the association between common psychosocial stress during pregnancy and the risk of a wide range of offspring diseases."

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3226491/

Based on "population-based sample of mothers with live singleton births (n = 66,203; 71.4% of those eligible)". (n = 66,203 is a respectable number)

Also it is exceptionally well referenced (~90 other bits of research referred to by my count).

Here is their definition of "stress": http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3226491/table/t1/

Here are some of my favourite findings:

The observed association between maternal stress during pregnancy and child health may represent long-term consequences of subtle adaptations in multiple organ systems to the intrauterine environment. The potential biological mechanisms underlying such developmental plasticity, including epigenetic processes and changes at the molecular, cellular, and organ level in the offspring.

...

Specifically, in relation to maternal stress during pregnancy, numerous subclinical alterations in physiology, including changes in immune, brain, cardiovascular, autonomic, endocrine, and metabolic function, have been described, such as changes in fetal heart rate, insulin resistance, increased concentrations of immunoglobulin E in cord blood and changes in hypothalamic–pituitary–adrenal (HPA) axis function[1]. .. Elevated stress levels across pregnancy have also been associated with changes in production of pro-inflammatory cytokines in the offspring[2].

...

Adjusting for maternal smoking during pregnancy, hypertension, and diabetes did not alter associations between maternal stress during pregnancy and child health. Maternal nutrition is another candidate mediator, because stress is related to quality of nutrition, and a relationship between nutrition during pregnancy and a range of offspring diseases has been well documented. ... Adjusting for birth weight and length of gestation had little effect on associations.

I was going to post this anyway before re-reading the beginning of the conclusion:

This study suggests that maternal life stress during pregnancy may be a common risk factor for a wide range of diseases in the offspring; however, we found almost no evidence for adverse health consequences of maternal emotional stress during pregnancy.

There seems to be some other research out there, though this paper is interesting.

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[1] changes in HPA axis activity have been associated not only with maternal stress during pregnancy (Kapoor et al. 2008), but also with a wide range of diseases, including mental disorders (Goodyer et al. 2001), respiratory diseases (Priftis et al. 2009), diseases of the skin (Buske-Kirschbaum et al. 2010), and infectious diseases (Bailey et al. 2003). However, although the HPA axis has long been proposed as a causal link between early adversity and lifelong disease risk.

[2] dysregulation of cytokine production has been associated with certain mental disorders (Conti and Fulcheri 2010; Raison et al. 2010); infectious diseases (Subauste et al. 1995); diseases of the eye, such as conjunctivitis (Niederkorn 2008); ear, such as otitis media (Smirnova et al. 2002); respiratory system, such as asthma (Finkelman et al. 2010); digestive system, such as disorders related to gastrointestinal motility (De Winter and De Man 2010); urogenital system, such as urinary tract infection (Mak and Kuo 2006); and skin, such as atopic dermatitis (Miraglia del Giudice et al. 2006).

Answer 4

Anecdotally I've been able to feel fetal movement since very early and again to confirm @anongoodnurses' excellent answer the amount and nature of fetus activity (insofar as I can feel it) seems to have a direct relationship with my level of activity and physical state. Less so my mental/emotional state.

Two cases for comparison recently of my sense of "stress" compared to fetus behaviour:

At 5 months pregnant I went on a large (last) round-the-world work trip and was very concerned for baby. Despite sleeping as much as possible, I was exhausted and found the travelling difficult. But while her activity schedule was shifted by timezones, baby seemed very happy and well, and seemed to enjoy the amount of walking I needed to do (no discomfort or aggressive activity from her at any stage -- only normal expected behavior) despite my personal fatigue and sometimes sense of duress.

Recently, at 6 months pregnant (and a programmer) I pulled a coding all-nighter -- something I used to do regularly but have not done since pregnant -- rest assured I've been very well rested all pregnancy and felt mentally and physically good or wouldn't have gone through with it. OTOH baby hated it, even though I felt good: on the afternoon of the sleepless day I suffered through 2 hours of very uncomfortable, aggressive tossing-and-turning and then the following day (after a good night's sleep) she went quiet for many hours -- I was ready to call the midwife I was so concerned, but I could feel some small movement. Within a few days she's returned to perfectly normal activity and schedule.