Girls born with unexpectedly low birth weights have been found to be twice as likely to be infertile in adulthood, warranting more research on pregnancy outcome that affects about 7.7 percent of all newborns.
Dr. Josefin Vikstrom and her colleagues at Linköping University in Sweden said in a press release that the findings illuminate an entirely new risk factor associated with low birth weight (LBW) and small for gestational age (SGA). “Women born with LBW or SGA seem to suffer an increased risk of infertility due to a female factor,” they explained. “Thus, infants born with birth characteristics that deviate from the norm may be at greater risk of difficulties in childbearing later on in life.”
The study, which is published in the journal BMJ Open, surveyed 1,201 Swedish women born after 1973 who were in a relationship and had previously sought help for fertility problems between 2005 and 2010. By analyzing medical records, the researchers determined that about four percent of the women were underweight at birth. Similarly, six percent were born unexpectedly small.
The team found that women with fertility problems attributable to a female factor were 2.5 times more likely to have been born with LBW compared to women whose fertility issues were attributable to a male factor or unexplained. The same women were also three times more likely to have been born SGA. The association persisted after the researchers controlled for previous motherhood, current weight, and other factors known to influence fertility.
Numerous past studies have explored the possible consequences of LBW. In a 2011 study from the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, researchers showed that people who are underweight at birth may have an increased risk of obesity later in life. Similarly, a study from the University of Pennsylvania School of Nursing found the prevalence of autism to be higher in LBW babies.
Vikstrom and colleagues wrote that several factors may underpin the association between LBW, SGA, and female fertility problems. One possibility is that growth restriction in the womb may come to the detriment of reproductive organs, affecting function later in life.
Although the sample size was relatively small, the team believes that the findings warrant further investigation. "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 concluded.
Source: Vikstrom J, Hammar M, Josefsson A, Bladh M, Sydsjo G. Birth characteristics in a clinical sample of women seeking infertility treatment: a case-control study. BMJ Open. 2014.