Researchers have found that girls who are born unexpectedly small or underweight are twice as likely to have fertility issues in adulthood than those born at a normal size. This is according to a study published in the journal BMJ Open.
They note that with advances in medicine, more underweight babies are surviving into adulthood, which could mean that the prevalence of infertility could also rise.
For their study, the team assessed data on all women born in Sweden from 1973 onward who were seeking infertility treatment at the Centre of Reproductive Medicine from 2005 to 2010.
In total, there were 1,293 women who participated, and they were all in a heterosexual relationship. The researchers analyzed cause of fertility from their medical records, and details on their birth size, age and weight were taken from the national medical birth register in Sweden.
Within the couples, infertility was attributed to females in 38.5% of the cases, to men in 27% of the cases, combined causes in 7% of the cases and unexplained in 28% of cases.
Additionally, while the majority of the women were of a healthy weight, around 1 in 4 was overweight, 1 in 20 was obese and 2.5% were underweight.
Overall, the researchers note, around 4% of the women had been born prematurely and about 4% were underweight at birth. Just under 6% of them were "unexpectedly small babies," they add.
Study could have major implications, but more research needed
Their findings reveal that women with fertility problems that were attributed to a female factor were nearly 2.5 times more likely to have been born underweight, compared with those whose infertility was due to a male factor or unexplained.
In addition, the team found that these women were nearly three times more likely to have been born unexpectedly small, compared with those whose fertility was unexplained.
And even after the researchers took into account factors that could influence the results - such as previous motherhood and current weight - they found that these findings held true.
The team observed that women whose infertility was attributable to a female factor were mostly heavier than average, and they note that excess weight is a known risk factor for infertility.
The study authors say their findings suggest that growth restriction in the womb could affect how reproductive organs develop, and they note that previous research has linked reduced ovulation with fetal growth restriction.
Though their findings are significant - and if confirmed, they may have implications for prevalence of infertility - the researchers caution that the sample size is quite small and the study was only carried out in Sweden, so the findings may not apply to other geographical locations.
"As medical research and care advances, more infants will be born [with low birthweight or small size] and survive, which in turn might influence future need of infertility treatment," they conclude, adding:
"Thus, infants born with birth characteristics that deviate from the norm may be at greater risk of difficulties in childbearing later on in life. Since this study is the first of its kind, more studies are needed to verify the associations."
Medical News Today recently reported on a study that suggested BPA may be linked to infertility in women.