Effects of chronic ingestion of caffeine on mammary growth and reproduction in mice.

Normal mammary gland growth and reproduction were examined in C3H/HeMei mice given caffeine as drinking water (500 mg/l tap water) after weaning on day 20 of age. Caffeine ingestion had little effects on any of the day of vaginal opening, body growth, pattern of estrous cycles, mammary gland growth and reproduction except for the rearing rate on day 12 of lactation. Five out of 12 mothers given caffeine lost all pups before day 12 and resulted in 51% of the rearing rate on that day, while that of the control was 91%. The rate did not change thereafter in either group. The results indicate that the chronic heavy ingestion of caffeine would induce the high mortality of pups during early stage of lactation.