A new study has unravelled the differential impacts of physical and psychological stressors during pregnancy on pre-term birth, child gender and neurodevelopmental outcomes.
Studies on prenatal programming – the impact of in utero factors on future health – have shown that “the womb may be more important than the home,” write Kate Walsh from Yashiva University in the Bronx, US, and co-authors.
Therefore, they “had good reason to believe stress would affect the growing infant,” says senior author Catherine Monk, from Columbia University Medical Centre in New York, US. But information on how much stress matters for children’s future health and which outcomes different stressors produce, independently of the postnatal environment, was lacking.
To explore this, the researchers analysed data from questionnaires, diaries and physical assessments in the early pregnancies of 187 healthy women and published their findings in the Proceedings of the National Academy of Sciences.
Exploring 27 indicators of psychological, physical and lifestyle stress, they found that while two-thirds of expecting mums were healthy, the rest showed two distinct profiles of clinically relevant maternal stress with different impacts on their babies.
One of those profiles was characterised by psychological indicators – perceived stress, depression and anxiety – and the other by physical factors: high blood pressure and greater caloric intake.
The impact of these stressors is not good news for parents secretly hoping for a boy: while the normal sex ratio is about equal, physically stressed mums were more than twice as likely to have a girl, with a male to female ratio of 4:9. This ratio was 2:3 in psychologically stressed mums.
But all parents should be cautious. Physically stressed mums had a one in five chance of delivering their baby pre-term – 1.5 weeks early – compared to one in 20 of their healthier counterparts.
Even though medical advances have increased survival rates of pre-term babies, premature birth still increases risk of death and neurodevelopmental disorders including cerebral palsy, intellectual disability and hearing impairments.
Foetuses of physically stressed mums were more likely to have heart rate patterns indicative of slower nervous system development, while those of psychologically troubled mums had more birth complications – consistent with other studies of babies from women with mental illness.
While the news about stressful pregnancies is troubling, there is a beacon of hope.
“[W]hat most differentiated the three groups,” says Monk, “was the amount of social support a mother received from friends and family.
“When social support was statistically made equal across the groups, the stress effects on preterm birth disappeared. Indeed, the more social support a mother received, the greater the likelihood of her having a male baby.”
The researchers suggest that social support is an achievable, target intervention, therefore, that could ease maternal stress and help infants thrive.
“What’s clear from our study is that maternal health matters, not only for the mother but also for her future child,” says Monk. “The womb is an influential first home, as important as the one a child is raised in.”
Natalie Parletta is a freelance science writer based in Adelaide and an adjunct senior research fellow with the University of South Australia.
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