The contraceptive or 'tube' implant is given to all Torean girls as they come of age as part of their extensive medical package. It monitors all vitals relevant to reproduction and effectively prevents pregnancy until it is switched 'on' by an encrypted radio signal. An activated implant almost ensures reproduction, with the probability for a successful pregnancy after a single intercourse exceeding fifty percent in most cases.
The activation signal - and the logic behind it - are a puzzle to most Toreans to the point that pregnancy is commonly seen as an 'act of god' that cannot be planned for or prevented. In fact, the Ministry of Improvements who is in charge of the population growth rate keeps a tight lip and it is wildly speculated that it is the AIs who still pull all the strings on reproduction.
As other forms of contraception are seen as redundant by the MoI, they are usually not available on Torei or even banned in some Ringdoms, a fact that could trouble offworlders, were it not for the many exotic pleasures that can be had on Torei, many of which pose no danger of pregnancy whatsoever.
Persistent reports of pregnancy without any sexual contact with a male, so called 'solo-births', give rise to the speculation that the tube implant may contain a cryogenically frozen sperm sample as a fail-safe against the loss of the relatively small male population. This would give the MoI - or the AIs - the ability to induce pregnancy in any woman, sexually active in a heterosexual relationship or not, and largely regardless of precautions taken. On the other hand, these reports could simply be the result of sperm contamination from an accidential source, which would be unsurprising given the hypersexualized nature of Torean culture.