text: Worldwide, nearly 85% of women experience one or more pregnancies 
  in their lifetime1, with 140 million women becoming pregnant each 
  year. Over an approximately 40-week gestational window, the maternal 
  body undergoes profound physiological adaptations to support the 
  development of the fetus, including increases in plasma volume, meta- 
  bolic rate, oxygen consumption and immune regulation2. These rapid 
  adaptations are initiated by 100-fold to 1,000-fold increases in hormone 
  production, including estrogen and progesterone. These neuromodu- 
  latory hormones also drive significant reorganization of the central 
  nervous system. Evidence from animal models and human studies con- 
  verge on pregnancy as a period of remarkable neuroplasticity3–10 (see 
  ref. 10 for one of the earliest known observations). Gestational increases 
  in steroid hormone synthesis drive neurogenesis, dendritic spine 
  growth, microglial proliferation, myelination and astrocyte remodeling 
  (for review, see ref. 11). These cellular changes are pronounced in brain 
  circuits that promote maternal behavior. For example, Ammari et al. 
  recently discovered that steroid hormones can fine-tune the response 
  properties of galanin neurons in the rodent medial preoptic area of 
  the hypothalamus (mPOA), leading to enhanced sensitivity in dams 
  to sensory cues from newborn pups12. 