December 31, 2019
2 min read

Boys born small for gestational age at higher risk for infertility as adults

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Boys who are born small for their gestational age, or SGA, have a higher risk for being diagnosed with infertility in adulthood, according to a Danish study published in Human Reproduction.

“SGA is caused by other factors, for example maternal factors, and if we want to intervene against ‘infertility,’ then these other factors may be explored further,” Anne Thorsted, MPH, a researcher in the department of public health at Aarhus University in Denmark, told Healio. “Our results show that sometimes we must look at the very early life to find explanations of health problems that occur later in life.”

Thorsted and colleagues used data from Danish health registers in two municipalities to determine the association between SGA and infertility. A total of 5,594 men and 5,342 women born between 1984 and 1987 were included for analysis, with data examined from the participant’s 8th birthday through Dec. 31, 2017. The researchers obtained birth weight and gestational age via birth records, and information regarding fertility treatment and infertility diagnosis from the Danish In Vitro Fertilization and Danish National Patient registries.

Men who were SGA had a 55% higher risk for infertility diagnosis or treatment compared with men born at appropriate gestational age (OR = 1.55; 95% CI, 1.09-2.21). This association decreased after men born with cryptorchidism or hypospadias were excluded (OR = 1.37; 95% CI, 0.93-2.01). They did not observe an association between women’s birth weight for gestational age and infertility risk (adjusted OR = 1; 95% CI, 0.73-1.37). The average participant age was 32.

Low birth weight has previously been shown to increase the risk for neurodevelopmental disorders and glomerular filtration rate decline.

One potential limitation of the study was that gestational age estimation is “associated with uncertainty,” which may lead to nondifferential misclassification, Thorsted said. The researchers also noted that genital malformations may be a partial cause of the association between SGA and infertility, and that further research is warranted.

“Being born SGA has a different effect on gender,” Thorsted said. “The potential mechanisms underlying the association observed among men in our study remain unresolved. Suggestions of a biological cause may be considered regarding research that shows a link between fetal growth restriction and development of hypospadias and cryptorchidism, two factors associated with impaired testicular function.” – by Eamon Dreisbach

Disclosure: Thorsted reports no relevant financial disclosures.