How do $Cu$-releasing Intrauterine Devices $(IUDs)$ function?

$A$: Periodic abstinence is a natural method of contraception in which couples avoid or abstain from coitus from day $10$ to $17$ of the menstrual cycle,when ovulation is expected.
$R$: Day $10$ to day $17$ of the menstrual cycle is considered a safe period.

$A$ : Intrauterine devices $(IUDs)$ are a very effective contraceptive method.
$R$ : $IUDs$ do not allow sperms to enter the uterus.

Most of the contraceptive pills contain

In lactational amenorrhoea,there is no ovulation or menstruation during the period of intense lactation following parturition,due to high levels of prolactin,which:

Lactational amenorrhea is . . . . . . .