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Risks of preterm birth and growth restriction in second births after a first-born male infant

Nicole C Loroña1, Sarah B Allen1, Esther W Lam1

  • 1Department of Epidemiology, University of Washington School of Public Health, Seattle, WA.

Annals of Epidemiology
|August 11, 2020
PubMed

Insights

Having a first-born male infant increases the risk of preterm birth (PTB), low birthweight (LBW), and small for gestational age (SGA) in subsequent pregnancies. These risks were not affected by the second-born infant's sex or paternity changes.

Area of Science:

  • Reproductive Health
  • Immunology
  • Perinatal Medicine

Background:

  • Maternal immune responses can be altered by the sex of a previous child.
  • A first-born male infant may trigger an exaggerated maternal immune response in subsequent pregnancies.
  • This can elevate risks for adverse pregnancy outcomes like preterm birth and growth restriction.

Purpose of the Study:

  • To investigate if infants preceded by a first-born male have increased risks of preterm birth (PTB) and growth restriction.
  • To determine if these associations are modified by paternity change or the sex of the second-born infant.

Main Methods:

  • A population-based cohort study utilized Washington State birth certificate data from 2003-2014.
  • Included were second live-born infants preceded by a first-born male (n=58,704) or female (n=58,704).
  • Stratified analyses estimated adjusted relative risks (RRs) for PTB, low birthweight (LBW), and small for gestational age (SGA).

Main Results:

  • Second-born infants following a first-born male showed higher risks of PTB (RR=1.14), LBW (RR=1.17), and SGA (RR=1.13).
  • Elevated RRs were observed for indicated PTB (RR=1.19), preterm premature rupture of membranes (RR=1.15), and spontaneous PTB (RR=1.12).
  • No significant differences in associations were found based on the second-born infant's sex or paternity change.

Conclusions:

  • A first-born male infant is associated with increased risks of PTB, LBW, and SGA in the subsequent infant.
  • These findings highlight a potential sex-specific immunological influence on pregnancy outcomes.
  • The results were consistent regardless of paternity change or the sex of the second-born child.
Abstract

Keywords:
Birth orderFirst-bornFirst-born maleGrowth restrictionLow birth weightPaternity changePreterm birthSexSmall for gestational age

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