Frequently asked questions
Female cats do not have menstrual periods and bleed like humans and some primates. Just like people, the lining of the uterus does develop in preparation for pregnancy; however, it is not shed in the way the uterine lining of females does.
Cats have a different reproductive cycle to us. They are seasonal maters and induced ovulators. As the number of daylight hours increases in spring, cats of sexually reproductive age will go through four reproductive cycles. If the cat becomes pregnant, she will no longer be receptive to males until two weeks after the birth of her kittens. If she is not pregnant, estrus (heat) will return every 2-3 weeks.
The feline reproductive cycle
|Proestrus||The period which precedes estrus, and is not noticeable in most cases, it lasts for approximately one day. Follicular growth occurs, which produces estradiol, which causes changes to the vaginal epithelium. Toms may be attracted to the queen, but she is not receptive to mating during this phase.|
|Estrus||Estrus occurs when serum levels of estradiol are at their peak. The female is now receptive to mating and will call (or yowl) loudly and roll on the floor to attract a male. Cats are induced ovulators and are dependant on the release of luteinising hormone (LH) from the pituitary gland in the brain. LH stimulates the follicle to release the eggs which travel down the fallopian tube. Release of LH is triggered by vaginal stimulation during copulation.|
Estrus lasts approximately 4-5 days; if she doesn’t become pregnant, estrus will occur again every 2-3 weeks.
|Postestrus (diestrus)||Following release of the eggs (ovulation), the follicle becomes a corpus luteum which produces estrogen for 30-60 days. This stimulates the development of endometrium (lining) in the uterus. If the cat is not pregnant, the corpus luteum and the endometrium regress. During this phase, the cat is no longer responsive to males.|
|Anestrus||The seasonal absence of cycling activity which occurs in the autumn and winter months as the period of daylight becomes shorter.|
The human reproductive cycle
|Menstrual phase (From day 1 to 5)||The uterus sheds the soft tissue and blood which lined the uterus; it is during this phase that the female period occurs.|
|Follicular phase (From day 1 to 13)||The pituitary gland secretes a hormone which stimulates the eggs in the ovaries to grow. During this time, the lining of the uterus begins to develop in preparation for a fertilised egg.|
|Ovulation phase (Day 14)||The mature egg is released and swept into the fallopian tube.|
|Luteal phase (From day 15 to 28)||The egg remains in the fallopian tube for 1 day. If it is not fertilised, it disintegrates, and the lining of the will be shed during the next menstrual period.|
Signs of estrus
Anybody who has had an entire female cat will be familiar with a cat in heat although some cats are capable of a silent heat, in which no visible signs are evident. Typically, a cat in heat (estrus) will display the following:
- Loud calling (or yowling) which is different to a cat’s normal meow, it can almost sound like the cat is in pain (she isn’t)
- Rolling on the ground
- Friendlier towards people
- Raising the tail and rear end when stroked
- Lowering her front legs and raising the rear end, in the presence of a male, this is known as lordosis
How do I know if my cat is pregnant after estrus?
Unlike humans, there are no pregnancy tests for cats, and it can be several weeks before pregnancy becomes apparent.
Cat pregnancy timeline:
- Some cats may experience morning sickness early in the pregnancy, including being less interested in food and occasionally vomiting.
- Increased appetite, especially as the pregnancy progresses. This typically begins around the third week of pregnancy. A pregnant cat’s nutritional needs will increase, particularly later in the pregnancy. There is more information on feeding the pregnant cat here.
- You may notice behavioural changes in your cat; she may become more affectionate.
- She may sleep more.
- Around 18-21 days, the nipples will be visibly swollen and rose coloured, this is known as “pinking up”.
- By three weeks, her belly will have become noticeably larger.
- Around three weeks gestation, your veterinarian will be able to perform an ultrasound on your cat to determine if she is pregnant.
- At this time, the veterinarian can also carefully palpate the abdomen and feel the developing fetuses (do not attempt this at home).
- In the later stages of pregnancy, the queen will look for a “nest” in which she can deliver and care for her kittens. This is usually a warm, quiet spot such as in a wardrobe or under furniture.
- The mammary glands (breasts) will start producing milk towards the end of the pregnancy.
Effects of repeated heat cycles in cats
It is easy to think ‘lucky cats, no period‘, however, several heat cycles which do not end in a pregnancy can cause a serious and life-threatening condition called pyometra, in which the female releases eggs (which could be from something as simple as a human stroking the cat) or a nearby male cat, and the lining of the uterus develops. Cats who have had multiple ovulations can develop an infection in the lining of the uterus. Pyometra can be open or closed. Cats with open pyometra have a discharge which escapes through the open cervix and out of the vagina. The cervix is closed in cats with closed pyometra, with nowhere for the pus to escape.
Symptoms of pyometra
As well as the possible discharge from the vagina, your cat may display some or all of the below symptoms:
- Anorexia (loss of appetite)
- Weight loss
- Normal, increased or decreased body temperature
- Excessive thirst and urination
- Distended abdomen
- Abdominal pain
A cat with pyometra must see a veterinarian immediately; the usual treatment is surgical removal the infected uterus.