Contraception
Contraception was a method of avoiding pregnancy. One option involved taking oestrogen in tablet form; (TV: Everything Changes) Bernice Summerfield took such a "little yellow pill" every day. (PROSE: The Squire's Crystal)
During Miracle Day, India and mainland China responded to the overpopulation crisis wrought by unmanaged immortality by putting contraceptives in the water supply.
Dr Rosenbloom suggested to a panel that they ought to consider the forced contraceptive option in the US as well, citing the life-long risks pertaining to miscarriage when survival to full-term had become a certainty. Dr Murphy was strongly opposed to this proposition. (TV: Dead of Night)
According to Jack Harkness, by the 2000s, contraceptives could be identified in Earth's rain. As Jack explained, oestrogen entered the water cycle when people flushed their contraceptive pills down the toilet: sending the hormone "all the way up into the sky, [then] all the way back down on to me". Jack further claimed that this was "feminising" the fish. Nevertheless, he was happy enough to avoid another pregnancy. (TV: Everything Changes)
Contraceptive implants were invented at some point before 2018. Rose Donnelly, secretly a time traveller named Gillian from the early 21st century, had approximately a year's worth of time-released contraceptive implants in her left arm, under the skin. For this reason, she claimed, pregnancy was an impossible outcome of sex with Sherlock Holmes. She was also innoculated for all the most common STDs. (PROSE: Erasing Sherlock)
As the Fifth Doctor discovered, the human colonists on F-four were unable to bear children because someone had genetically engineered the colonists' original seed supplies to produce a particular contraceptive. For this reason, conception was impossible, and even those who fasted during pregnancy would miscarry as soon as they ate again from the crops. This contraceptive gene was placed by Earth's government, who realised that the colonists had been infected with a deadly virus, which might spread across Earth should they return. The colonists on F-four were effectively neutralised through infertility. (PROSE: No Exit)
