In order to adopt Billings Method for fertility regulation during the period of breast feeding, cervical mucus was observed and monitored in 61 breast feeding mothers.Urine estrogen and /or pregnanediol were/was measured in 15 breast feeding mothers. Observations on cervical mucus during 244 months were collected. The type of dry or no mucus was observed in 75.27% fully breast feeding mothers. Constant unchanging mucus was observed in 69.39% partially breast feeding mothers. Developmental changing mucus was observed in 79.25% of mothers bottle feeding their infants. According to the record on cervical mucus within 6 months postpartum, 97.14% of the cervical mucus was consistent with normal menstrual cycles. Urine estrogen and /or pregnanediol were/was measured in 15 breast feeding mothers. The level of estrogen in urine averaged 0.08 μmol/24 h in fully breast feeding mothers and 0.14 μmol/24 h in partially breast feeding mothers.The peak level averaged 0.21 μmol/24 h in bottle feeding mothers.The pregnanediol level was determined to confirm ovulation in bottle feeding mothers. The average levels of cut off and the period of ovulation in 6 bottle feeding mother were 7 μmol/24 h and 9 μmol/24 h respectively.Measurement of urine estrogen and pregnanediol level all matched with cervical mucus appearances. Conclusion: Billings Method is a simple, scientific method for contraception without side effects during breast feeding period. In order to adopt Billings Method for fertility regulation during the period of breast feeding, cervical mucus was observed and monitored in 61 breast feeding mothers. Urine estrogen and / or pregnanediol were / were measured in 15 breast feeding mothers. Observations on cervical mucus during 244 The number of dry or no mucus was observed in 75.27% of fully breast feeding mothers. Constant unchanging mucus was observed in 69.39% of partially breast feeding mothers. Developmental changing mucus was observed in 79.25% of mothers bottle feeding their infants. To the record on cervical mucus within 6 months postpartum, 97.14% of the cervical mucus was consistent with normal menstrual cycles. Urine estrogen and / or pregnanediol were / were measured in 15 breast feeding mothers. The level of estrogen in urine averaged 0.08 μmol / 24 h in fully breast feeding mothers and 0.14 μmol / 24 h in partially breast feeding mothers. Peak l evel averaged 0.21 μmol / 24 h in bottle feeding mothers.The pregnanediol level was determined to confirm ovulation in bottle feeding mothers. The average levels of cut off and the period of ovulation in 6 bottle feeding mother were 7 μmol / 24 h and 9 μmol / 24 h respectively. Measurement of urine estrogen and pregnanediol levels all matched with cervical mucus appearances. Conclusion: Billings Method is a simple, scientific method for contraception without side effects during breast feeding period.