Fig. 1.

Variation of relative levels of estrogen (pink) and progesterone (blue) levels across a the menstrual cycle, b the oral contraceptive pill cycle, c pregnancy and the postpartum period, and d the menopause transition. Timing of structural MRI scans of reviewed studies shown based on an idealized 28-days cycle menstrual cycle, gestation length of 40 weeks, and menopause at 50 years. Menstrual cycle length may vary physiologically from 21 to 35 days. ^†Study resulted in more than 1 publication. ^‡Specific day ranges of scan timing was not reported, so ranges are estimated based on text descriptions. *Subjects were scanned beyond 6 months postpartum. Oatridge et al. (2002) also scanned two subjects before conception. **Women were scanned up to age 77