A child's chance of developing an allergy could depend on the season in which the youngster was conceived, experts said today.
Babies whose first three months in the womb occurred in springtime are more likely to suffer from food allergies, such as to milk and eggs.
About 11% of children whose 11th week of development in the womb was in April or May were more likely to suffer food allergy, a study found.
This compared with 6% of children whose 11th week was in December or January.
Overall, the April/May group was three times more likely to be sensitive to milk and eggs than the December/January group.
Experts have already shown a link between pollen and food allergies, and the latest study supports this association.
Checks on pollen levels over the study period showed that levels of birch and alder pollen peaked during April and May.
The research, published in the Journal of Epidemiology and Community Health, involved 5,973 children born between April 2001 and March 2006 who lived in south-east Finland.
Of this group, 18% had tested positive for food allergies by the time they were four.
The results showed that by this age, sensitivity to food allergy varied according to month of birth, from 5% of children born in June/July to 10% for October/November.
Previous research has shown that babies born in autumn or winter are more prone to eczema and wheezing, identified by higher levels of circulating antibodies to allergens in their blood than those born in spring or summer.
Experts believe babies in the womb begin to produce antibodies at around the 11th week of development. Antibodies to specific allergens develop by around 24 weeks.
The authors, from Oulu University Hospital in Finland, said: "We found a higher incidence of positive results in food allergy tests among children born in October or November than among those born in other months in an unselected population.
"The incidence of such results was particularly high and especially pronounced for milk and egg among children who had their 11th gestational week in April or May, the season during which the concentrations of pollen from birch and alder are highest in the area concerned.
"Children whose 11th gestational week falls in April/May might also be more heavily exposed than other children to viral infections and deficiency of vitamin D in their neonatal period occurring in mid-winter, which may also have an impact on their immunological development."
George Du Toit, consultant in paediatric allergy at St Thomas' Hospital in London, said: "Although interesting, and in keeping with other study findings in this field, the findings are not of a significance that would warrant changes in families that wish to minimise allergy outcomes in their offspring."
He said while seasonal environmental factors during pregnancy could interfere with the process of developing antibodies, such a link remains controversial.