Physiological bases of contraception Lecture -6 Dr. Zahoor Dr. Shaikh Mujeeb Ahmed

Contraception Is prevention of pregnancy before the implantation has taken place .

Methods of Contraception Blockage of sperm transport to ovum Natural Methods Rhythmic abstinence Coitus interruptus Barrier methods Use of spermicidal Sterilization tubal ligation vasectomy

Methods of Contraception (cont…) Prevention of ovulation Hormonal contraceptive (OCP) Blockage of implantation IUCD Emergency contraception/morning after pill

1. Blockage of sperm transport to ovum Natural methods Rhythmic abstinence Coitus interruptus periodic or rhythmic abstinence i.e. avoidance of sexual intercourse during woman’s fertile period Following methods are used Calendar method: The women predicts when ovulation to occur based on keeping careful records of previous cycles

Basal body temperature method: Body temperature rises slightly a day after the ovulation safe period is considered to begin after the basal body temperature remains elevated for 3 days Coitus interruptus: withdrawal before ejaculation

Barrier methods Barrier methods: prevents entry of sperm into vagina or uterus For males (condom) For females ( diaphragm or cervical cap ) Sponge Placing Spermicidal Agents : Kill the sperms or decrease their motility Suppositories Gel Foam tablets Creams

Sterilization Permanent Methods Female sterilization ( i.e tubal ligation or Tubectomy) Male sterilization (vasectomy):

2. Prevention of ovulation Hormonal contraceptive Oral contraceptives Combined pills Estrogen alone Synthetic Progesterone alone Injectable .

Hormonal contraceptive(continued) Oral contraceptives Contains synthetic estrogen and progesterone like steroids (ethinyl estradiol & norgesterel/norethesterone) Tablets are taken once daily for 21 days commencing at 5th day of menstrual cycle ,it is than stopped for 7 days during which time bleeding occurs

Mechanism of action: They act by inhibiting the release of FSH & LH by anterior pituitary by negative feedback mechanism, preventing the development of graffian follicle ,ovulation & formation of corpus luteum is prevented. Increases viscosity of cervical mucus ,preventing the sperm penetration Endometrial maturation is also altered preventing blastocyst implantation

Hormonal contraceptive(continued) Injectable long acting prgestational preparation which can be given once in a three months Sub cutaneous implants of progesterone have also been tried ,(can prevent pregnancy up to 5 years) Dermal patch

3. Blockage of implantation Intra Uterine Contraceptive Device(IUCD): Are devices which are introduced & left inside the uterus for longer period of time . Mechanism of action : They produce local nonspecific inflammatory reaction in the endometrium & disturbing the endometrial cyclic changes & prevent implantation of blastocyst .

Intra Uterine Contraceptive Device(IUCD):

Intra Uterine Contraceptive Device(IUCD)(continued) Side effects : Bleeding Abdominal pain / backache Displacement Perforation

Average failure rates of common contraceptive techniques Contraceptive method Average failure rate (100 women-year) Natural method 20-30 Chemical contraceptive 20 Barier method 10-15 OCP 2-2.5 IUCD 4

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