Practice nurses are being warned to look out for tell-tale signs of stress in pregnant women during their antenatal care.
The baby charity Tommy's found that nine out of 10 women feel stressed during pregnancy, with many worrying over certain "taboo" subjects.
A survey discovered 20% of women secretly fear they may not love their baby, while a similar number worry they may never want to have sex again.
More than one in 10 say they are depressed because they are unable to reveal their pregnancy, while 8% are worried they might not want their child.
And around a third of women are concerned about developing postnatal depression.
A number of scientific studies have shown that suffering stress or depression can affect an unborn child as early as 17 weeks into the pregnancy.
Philip Baker, a professor of maternal and fetal health from Manchester, said: "Current research under way at Tommy's Manchester Unit indicates that significant levels of stress can limit the growth of babies within the womb.
"The Tommy's study also suggests that stress increases the risk of preterm labour, with this effect proving most impactful when stress is experienced around the time of conception and in early pregnancy."