The month of the year a baby is conceived appears to increase the chances of premature birth, new research suggests.
The researchers found that children conceived in May faced a 10% increase in risk, relative to babies conceived at other times of the year.
The authors of the study believe that this could be a function of the pregnant mother's increased exposure to seasonal flu in January and February, exactly when a baby conceived in May would approach the full term.
"We were surprised that the relationship between potential exposure to influenza and premature birth appears to be so evident in the data," said the study's author. Janet Currie, director of the Health and Welfare Center of the Woodrow Wilson School of Princeton University .
"Some recent work has suggested that influenza can induce premature labor in women late in pregnancy, and our results seem to corroborate it."
Currie, who carried out the study with the researcher Hannes Schwandt, He added that if pregnant women are vaccinated against the flu, they may not be at risk of premature birth due to that infection.
The findings appear online in the current issue of the journal Proceedings of the National Academy of Sciences. The study found an association between the month of conception and premature birth, but did not prove causality.
To explore the potential impact of conception on child health, the researchers analyzed data from approximately 647,000 mothers in the northeastern EE region. UU All had given birth to more than one child.
In addition to the dates of birth and duration of pregnancies, the data included information on changes in weight, race, education and the mother's smoking history.
The research team noted that by looking exclusively at experience from conception to the birth of more than 1.4 million siblings (rather than unrelated babies), they were able to compare apples to apples, and evade other factors that could complicate the risk of prematurity. , as the wealth of the family or the educational level.
The result is that the authors identified a "marked depression" in the duration of pregnancies that began in March.
By more in-depth comparisons of birth and conception records month by month together with data on influenza from 1997, which had been collected by the US Centers for Disease Control and Prevention (CDC) UU , the team found a correlation between conceptions in May and a notable increase in influenza exposure in the third trimester of those pregnancies.
In addition, babies conceived in the summer months tended to weigh a little more than those conceived at other times of the year.
"The results of birth weight suggest that babies conceived in summer have a higher birth weight, in part because mothers tend to gain more weight during pregnancy when they conceive in summer," Currie said. "It seems likely that it is because they have a better diet, although we can not observe that directly with our data."
"We can not rule out other factors that could also be important for pregnancy outcomes," he said. "But we believe the moral of our article is that parents should take steps to protect themselves from known problems," suggesting that the most practical thing for pregnant women to do is simply eat well and get vaccinated against seasonal flu.
"That would probably be a more sensible method than trying to avoid conceiving in May."
Two doctors from Scott & White Healthcare in Texas d They wrote the study as "interesting", at the same time emphasizing that pregnant women should be vaccinated against the flu.