The Missing Siblings of Infants Born Preterm

Area of Science:

• Perinatal Epidemiology
• Reproductive Health
• Pediatrics

Background:

• Previous studies indicate parents of very or extremely low birth weight infants have fewer subsequent children.
• The impact of less preterm birth on subsequent childbearing remains unknown.

Purpose of the Study:

• To assess the quantitative contribution of infant gestational age to parental subsequent childbearing.
• To determine if preterm birth, regardless of severity, affects the number of future children.

Main Methods:

• Nationwide cohort study of 230,308 singletons born in Finland (1987-1990).
• Multivariate Cox regression models used to assess the impact of gestational age on subsequent live births.
• Analysis stratified by the number of previous children.

Main Results:

• Mothers of extremely preterm infants (23-27 weeks) were less likely to have subsequent children (aHR 0.74).
• Reduced likelihood of subsequent births observed across all preterm categories (28-31 weeks: aHR 0.72; 32-33 weeks: aHR 0.82; 34-36 weeks: aHR 0.90).
• The number of "missing siblings" (142 per 1000 preterm births) exceeded the number of preterm infant deaths (44 per 1000 preterm births).

Conclusions:

• Families with a preterm child have fewer subsequent children.
• Preterm birth significantly impacts family size, with "missing siblings" being a major population-level consequence.
• This effect is observed even in high-income countries and across various degrees of prematurity.