Table 1

Prenatal, perinatal, and early postnatal sex differences in lung growth and development

AgeDevelopment periodMorphology and physiologySex differences in morphology, maturation, and physiology
1–5 weeksEmbryonic33 Morphology: Lung bud formation24 33
6 to ∼15 weeksPseudoglandular33 Morphology: Differentiation of airways; airway branching pattern complete by 16 weeks24; airways smooth muscle appears in trachea and starts to contract spontaneously38
Ciliated goblet cells appear at ∼12 weeks15 38
16 to ∼26 weeksCanalicular33 Morphology: Vascularisation occurs: acini develop24; Clara cells appear by 26th week15 24 38; fetal respiration begins to influence lung development41 44 45 Morphology: No sex differences in relationship of lung growth to somatic growth40
Maturation: Mouth movements in female more advanced than male fetus34
26 to ∼36 weeksSaccular33 Morphology: Alveoli first appear at 30 weeks and are uniformly present at 36 weeks; air space wall thickness declines rapidly after 28 weeks15 38 Morphology: See above40
Maturation: See above: also female fetus approximately 1.5 weeks ahead of male in lung phospholipid profiles which reflect surfactant production and maturation44 46
Rapid increase in lung volume40
Perinatal and postnatal
36–40 weeks Morphology: Alveolar multiplication occurs24 Morphology: See above under 16 to ∼26 weeks40
As gestation advances bronchial smooth muscle increases relative to size of airway38 Maturation: More advanced in female than male lungs: see above under 16 to ∼26 and 26 to ∼36 weeks
Physiology: Female lungs have lower specific airway resistance than male lungs39
Birth to ∼1 week Morphology: Proportion of goblet to ciliated cells increases.38 Rapid alveolar multiplication continues.33 Proportion of goblet to ciliated cells increases rapidly38 Physiology: Neonates have proportionately larger airways relative to lung volume (FRC),27 higher size corrected forced expiratory flow rates40 41 43 and lower specific airway resistance than older infants39 Morphology: Female lungs smaller than male lungs, may have fewer respiratory bronchioles24
Maturation: More advanced in female than male lungs,44 46 premature female lungs less at risk for RDS44 and transcient tachypnoea of the newborn47 than male lungs and more responsive to hormone accelerators of surfactant production44
Physiology: As above under 36–40 weeks39
1 to ∼52 weeks Morphology: Formation of single capillary network occurs and alveolar multiplication continues,33 growth more or less linear with age at least up to age 224
Physiology: Airway resistance increases rapidly to adult levels in the first year of life39
Morphology: See above under birth to 1 week15 24
Maturation: Female lungs more responsive than male lungs to hormones44
Physiology: See above under 36–40 weeks,39 female infants also have higher absolute as well as size corrected forced expiratory flow rates than male infants40
  • Compiled from references 15, 24, 27, 33, 34, 3841, 4446.

  • 1-150 Prenatal age expressed as weeks after conception.