NOTE: In "Rhythm or safe period by calendar," a woman's fertile period is determined by counting the days from the start of her period that month. The woman abstains from sexual intercourse on her fertile days.
National Survey of Family
Growth Staff
Division of Vital Statistics
National Center for Health Statistics
7th Floor
3311 Toledo Road
Hyattsville, MD 20782
(301) 458-4222
National Center for Health
Statistics
3311 Toledo Road
Hyattsville, MD 20782
Phone:
1-800-232-4636
cdcinfo@cdc.gov
Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA 30333, U.S.A
Tel: (404) 639-3311 / Public Inquiries: (404) 639-3534 / (800) 311-3435