Washington, Feb 7 : A new research has cited that babies born to teenage fathers have an increased risk of having birth problems ranging from pre-term delivery or low birth weight, to death in or near to the time of delivery.
On the other hand, the study also found that older fathers, aged 40 and over, were not at increased risk of having babies affected by these problems. The results of the study were however independent of the age of the mother or other maternal factors that might be expected to have an impact on birth outcomes.
The study by researchers from the Ottawa Health Research Institute, Canada, is the largest of its kind on the effects of paternal age on adverse birth outcomes.
The researchers used data from the National Center for Health Statistics for nearly all the births (99pct) in the USA between 1995-2000, a cohort of more than 23.6 million births.
Later, they examined 2,614,966 singleton babies born live to married women having no childbearing histories, between 20-29 years of age, where there was complete information on paternal age, race, maternal education, prenatal care, and gestational and birth weight.
As it is already known that fathers between 20-29 years of age have the lowest risk of adverse birth outcomes, the researchers used this age group as the reference group to compare all the other age groups against.
When the reference group was compared after adjusting for confounding factors (such as race, education, smoking and alcohol drinking during pregnancy, adequacy of prenatal care and the sex of the baby), it was found that babies born to teenage fathers (aged less than 20) were more likely to be born early (a 15pct increased risk).
They were also found to have low birth weight (13pct increased risk), were small for gestational age (17pct increased risk), have a low Apgar score (13pct increased risk) or die within the first four weeks after birth (22pct increased risk) or die in the period from four weeks to one year after birth (41pct increased risk), however in all cases the absolute risk of death remained less than 0.5pct .
The results also indicated that fathers aged 40 or over did not have an increased risk of these adverse birth outcomes.
"Our study indicated that being a teenage father was an independent risk factor for adverse birth outcomes, whereas advanced paternal age was not. The paternal influence of younger fathers on adverse birth outcomes clearly warrants further investigation, and may lead to a deeper understanding of the causes of such outcomes," said Professor Shi Wu Wen, one of the authors of the study, senior scientist at the Ottawa Health Research Institute and professor at the University of Ottawa.
He added: "Although the increased relative risks for most outcomes were small, the magnitude of the risks to society could be huge, given the number of births worldwide, if the increases we found are truly attributable to paternal age."
It was mentioned in earlier studies that younger men can have lower sperm counts, semen volume, total numbers of spermatozoa and percentage of motile sperm. Immature sperm may be associated with adverse birth outcomes, possibly as a result of the abnormal formation of the placenta in the uterus (placentation).
"The mechanisms by which being a teenage father may contribute to an increased risk of adverse birth outcomes are not clear. Both biological and socio-economic status might play some roles in the observed findings. It is biologically plausible that paternal age might play a role in the risk of adverse birth outcomes associated with abnormal placentation," said Prof Wen.
There can also be some social explanations also: "Young fathers are more likely to come from economically disadvantaged families and to have lower educational attainment. Socio-economic factors such as education and occupation are known to be associated with a number of health outcomes. People from less affluent backgrounds are less likely to utilise prenatal care services, which is associated with an increased risk of adverse birth outcomes," explained Prof Wen.
Other social factors that might play a role, perhaps by adversely affecting the mother's health, include domestic violence, lack of financial or emotional support, paternal illicit drug use, smoking and alcohol drinking.
The study was published in Europe's leading fertility journal Human Reproduction.