Birth control in the queen

Most responsible cat owners want to prevent unplanned breeding and the production of unwanted kittens. Most forms of birth control prevent the heat cycle of queens, and so mating and conception does not occur. The cycle can be controlled permanently or temporarily. Pregnancy prevention is also possible after an unplanned mating has occurred.

The reproductive cycle in queens is very different from that in women. Queens usually undergo oestrus cycling (also known as ‘heat’ or ‘season’) between one and three times every 12 months, although there is a degree of individual variation in this. Oestrus is the time at which mating, and hence pregnancy, may occur.

Queens usually develop a regular cycle and any alteration of this cycle should be taken seriously. Occasionally, factors such as ill health can act to delay or suspend oestrus cycling. Unlike women, queens do not experience a menopause and usually continue to have seasons throughout life.

The first oestrus period (puberty) usually occurs between 6 and 12 months of age, when the queen has reached 80% of her adult size. Large breed queens may be older, e.g. 12-18 months, when their first oestrus period occurs. Sometimes this initial oestrus is missed by owners as the physical signs may be subtle and not last for long.

The normal oestrus cycles lasts around 3 weeks in the queen, and can be divided into a number of distinct stages:


Usually lasts for around 9 days. In pro-oestrus the vulva becomes swollen with a red (bloody) discharge. Male cats may show interest in queens in pro-oestrus, but the queen will not allow mating.


Lasts around 9 days. The bloody discharge typical of pro-oestrus is reduced. This is the time when queens will allow mating.


Lasts around 45 days. After oestrus the same hormonal changes occur in the queen whether or not she is pregnant. During dioestrus, levels of progesterone rise. Dioestrus ends spontaneously in the non-pregnant state, and with whelping in the pregnant state. It is this part of the cycle that can result in a ‘false pregnancy’.


The 3-4 month period between oestrus cycles. In this period the uterus shrinks down and repairs. The reproductive system is outwardly inactive during this time.

There are 4 ways to prevent pregnancy in the queen.

  • Avoidance of male cats whilst in heat.
  • Neutering (spaying).
  • Chemical prevention of the oestrus cycle
  • Chemical intervention after unintended mating.

Avoiding male cats

This is a possible method of natural birth control. It relies on a firm understanding of the normal oestrus cycle (see above) on the part of the owner of an entire queen. Extreme care must be taken during the receptive oestrus period. Not only are male cats very resourceful at gaining access to queens in heat, but the queens themselves may stray during this period if they get the opportunity.

Nevertheless, with responsible cat ownership on the part of owners of both queens and male cats, this should be a possible method of birth control. This method of birth control is often used by owners who wish to breed from their queen at some time in the future.

Neutering (spaying)

This is the most common method of birth control, and is a permanent, surgical method of preventing oestrus cycling and therefore pregnancy. An operation known as ovario-hysterectomy is usually performed, i.e. the ovaries and uterus are removed surgically. Ovariectomy (removal of the ovaries only) is a less common method of surgical neutering that is performed in some countries. In either case removal of the ovaries stops reproductive cycling and conception is impossible.

Surgical neutering is a major procedure but most vets perform the procedure frequently, and the risk is relatively low. Most animals being neutered are young and fit. The procedure can safely be performed before puberty, (even in cats as young as 6 weeks of age). Early neutering has an additional health benefit – it results in a diminished chance of mammary (breast) cancer occurring later in life.

Chemical prevention of the oestrus cycle

Birth control can be employed using various drugs similar to natural reproductive hormones. The drugs are administered by injection or as tablets at specified intervals, and it is very important that veterinary advice is followed as regards the treatment programme. The drugs used can prevent or shorten oestrus cycles but many have potentially serious side effects which should be discussed with your vet.

This method is similar to human contraception, but the potential risks mean that it is not generally considered desirable for on-going, long-term birth control in pet cats. It may be used as a short-term measure, or as a permanent measure only in cats that for some reason cannot undergo conventional surgical neutering.

If your queen has been mated unintentionally contact your vet as soon as possible. Your vet will be able to discuss the options for terminating pregnancy if it occurs. Immediate treatment can be given (similar to the use of the ‘morning after’ pill in human females). All drugs used in the prevention of pregnancy have potentially serious side-effects and should be used as a last resort rather than a method of birth control.

If your queen has been mated unintentionally your vet may advise neutering your queen to prevent this and future pregnancies. If you want to breed from your queen later, treatment should be delayed until pregnancy has been confirmed.

Queens should be neutered when their reproductive tract is inactive (during the anoestrus phase). The best time is around two to three months after the end of the previous oestrus. There is more risk of bleeding if the operation is performed during oestrus, and the surgery is technically more difficult at this time. Early spaying of queens helps prevent mammary (breast) cancer in later life.

This is a serious infection of the womb, seen most commonly in older un-neutered queens. Queens with pyometra are often very seriously ill and emergency treatment is usually required. Pyometra is best treated by surgical removal of the womb, but the risks are higher.

False pregnancy occurs ‘naturally’ at the end of dioestrus (see above). Some cats have very exaggerated symptoms and may show:

  • Poor appetite, lethargy and depression
  • Nest building behaviour and ‘adopt’ toys
  • Behavioural changes, including aggression
  • Mammary development and milk production

Such queens tend to have recurring false pregnancies at every oestrus and symptoms may last for weeks. Drug treatment can help during the false pregnancy, but the best solution is spaying, after the false pregnancy has ended. If your queen has suffered a false pregnancy discuss the options for treatment with your vet.

The reproductive cycle in the queen is complicated and during this time your cat will undergo many hormonal changes which can alter her health and temperament. If your queen is not neutered you should be familiar with all the natural changes in her cycle so that you can be alert to any signs of problems. If you do not plan to breed from your queen discuss the option of permanent neutering with your vet.