Feline Pregnancy Due Date Calculator

Female cats are induced ovulators, which means that the queen must be stimulated by the spines on a male cat’s penis before she can produce enough luteinising hormone for her eggs to mature. It takes a minimum of four acts of coitus before the luteinising hormone is strong enough in her system to cause her ovarian follicles to release their mature eggs.

Like humans, potentially damaging substances should be avoided during the early stages of pregnancy, and care should be taken with the types of vaccines used as well as medication. Responsible breeders will ensure that they never mate a queen who is not fully vaccinated and in perfect health before she conceives, so as to reduce the need for medication during her pregnancy.


(65 is the average)

Your Kitten’s Development During Pregnancy

Day 1: This is the date of the first act of coitus between male and female. The sperm reach the womb 30 minutes after mating, but must wait until her eggs are mature enough to be released into the female’s oviducts. Her eggs will only be viable for 24 hours, so queens should not be kept with the stud for more than three to five days, otherwise it becomes very difficult to predict the date on which the kittens will be born.

Day 2: The ovarian follicles release their mature eggs into the oviducts, ready to be fertilised by the waiting sperm.

Day 3: The first division of cells occurs within the fertilised egg, now called the blastocyte.

Day 4: The lump of around 30 cells is now called blastula. It forms a sphere of around 0.6mm in diameter.

Day 5: The blastulas release steroids to propel themselves down the oviducts into the uterine horns.

Day 6: Each blastula now forms a cavity, surrounded by 60 to 80 cells, which will later form the digestive tract. The outer cells of the blastula begin to form the placenta. As each blastula implants itself into the uterine wall, it releases a hormone which stops other blastulas from implanting nearby, and thus each kitten will have enough space to develop. They are now called embryos, and cells continue to multiply.

Day 8: The cells in each embryo now fold themselves into three layers, which will go on to form distinct parts of the future foetus. The embryos now measure 1.5mm by 1mm.

Day 13: Cells begin to develop into organs and the skin is formed.

Day 14: The placenta begins to form. The spinal cord begins to develop.

Day 15: The head and the tail can now be distinguished, and the circulatory system is beginning to develop. Testosterone is produced by male embryos, and this enters the bloodstream of the mother and other kittens via the placentas. If a female is placed between two males, she is likely to be more aggressive than normal females, and her sexual organs can sometimes be overly masculine for a while after birth.

Day 17: The embryo is 10mm by 2mm. The gastrointestinal system has developed, and the mouth is forming as well as the cerebellum. One can distinguish the placement of the eyes and ears now.

Day 18: The embryo measures 16mm by 5mm. The neck and tail curve towards each other. The forlegs are developing.

Day 19: The embryo measures 18mm long by 7mm wide, and the hind legs begin to develop. The primitive cerebrum and brainstem are in place now.

Day 20: The embryo now measures 24mm by 10mm. The eyes have colour, the forlegs have an internal skeleton and the rudimentary circulatory system is now carrying blood. The kittens’ hearts are the size of a pinhead, and beat at 230 beats per minute, as opposed to the adult rate of 140 beats per minute. The internal organs are all formed and the spinal cord reaches into the tail. The queen now begins to show signs of pregnancy such as enlarged, pink nipples, and even nausea with vomiting. Feeding several small meals a day might help. An experienced person can carefully feel her abdomen and count the tiny, pea-sized foetuses.

Days 21-23: The embryo measures 30mm by 13mm, and it’s skeleton is made of cartilage. Ear-holes are noticeable, and in the face, the tongue and palate are formed.

Days 23-25: Each embryo measures 34mm by 17mm. Toes begin to separate in the forlegs, and the toes begin to be distinguished in the little paddle shape at the end of each hind leg. The brain develops a bit more as does the spinal cord and nervous system.

Days 25-28: It is at this stage, when they are virtually complete, that the embryos become known as Foetuses. They measure 40mm by 21mm and their heads develop a chin, mouth, nose and cheeks, and teeth are present in their jaws. Little skeletons, formed of 247 bones, begin to calcify. Their digits begin to form paw-pads, and 30 distinct muscles develop in and around the ears to allow independent movement.

Days 28-32: The foetus measures 50mm by 25mm and they become difficult to differentiate on palpation of the queen’s abdomen. Small triangular ears are formed now and their inner ears are developing into organs that will be able to hear the footsteps of a mouse at 9 meters away, and will distinguish sounds two octaves higher than humans. Female kittens develop their wombs and the bladder now develops. Although the teeth are hidden under their gums, pressure receptors develop under each canine to help the cats determine when and how to deliver the killing bite to their prey. Eyelids seal the eyes shut to protect the developing cornea from the urine which is being secreted into the amniotic fluid by the newly formed kidneys. Nerves in the whisker pads are being formed, which will enable the cats to spatially orientate themselves and negotiate tight spaces. The queen’s food can now be increased, and she should be fed a premium quality food for kittens which contains more appropriate nutrients for the developing foetuses.

Days 32-38: The queen is now noticeably bigger, and the foetuses measure 60mm by 35mm. Nerves and muscles are developing, which enables more dynamic movements such as kicking, stretching, running. On scans, kittens can be observed to kick and head-butt their siblings as space becomes tighter. They do not yet have fur, but claws are formed on their toes, external genitals are now obvious and the iris is formed in the eye.

Days 38-43: The foetus is 80mm by 50mm. The skin becomes thicker and begins to wrinkle. Ears become bigger and the tail lengthens. The queen now spends more time grooming and her teats enlarge in preparation for feeing her kittens.

Days 43-48: The foetus is 94mm by 59mm, and silky fur is developing on its body which shows some pigmentation. The queen may begin to search for a suitable place to have her kittens and now is a good time to introduce her to her nesting box.

Days 48-52: The kittens measure 125mm by 65mm. The chest inflates and the lungs fill with amniotic fluid and practice breathing movements which can induce hiccups. The foetuses practice grooming, like wiping their paws over their mouthes. 2 Million hairs develop in the nose, to help sense smell. The kittens now have 70 taste buds and tiny spikes develop on the surface of their tongues to help them groom and rasp meat. The queen can lose her appetite as her abdomen becomes too crowded with kittens. Feed small meals often to keep her energy levels up. A cat drinking fountain can be helpful to ensure that she gets plenty of fresh water to help her to process and replace the kittens’ amniotic fluids. Our queen drinks around 500ml to 1 litre of fresh water per day at this time, and it is imperative to keep her litter box smelling clean and fresh as she uses it more often to eliminate the kittens’ waste. This is the time to advise your vet that your queen is expecting kittens, so that they can be aware of potential emergency appointments in case of delivery problems.

Days 52-58: This section of the calendar is still under development!

Days 58-birth: The kittens now measure 186mm by 60mm. After the 60th day, their organs are all sufficiently developed to ensure that if they are born now they will be viable. They are now putting weight on, ready to be born. Although gestation usually lasts 63 days from fertilisation, the delivery date is usually calculated from the first day of mating, which brings the expected pregnancy duration up to 65 days. If the pregnancy lasts for more than 69 days, it can be wise to consult your vet, just to check that all is well. If you are able to, it is possible to determine the onset of labour by taking the rectal temperature of the queen every day in the last few days. 24 hours before she is due to deliver her kittens, her temperature will drop by around 1 degree, from 38.5 Celsius to 37.5 degrees Celsius.

Birth: Each kitten weighs approximately 100 grams at birth. The birthing process begins with dilation of the queen’s cervix, and she will produce some blood-tinged, pinky mucus from her vagina as this happens. You may not see this process, as she is likely to clean this up herself, if she can reach around her abdomen. This first stage of labour can last 36 hours, but so long as the queen is relaxed and calm, and you are around to keep an eye on things, there is nothing to worry about. She will likely purr to release endorphins into her bloodstream, and this causes her to relax and helps to ease pain during contractions. You will be able to feel her contractions by placing a hand on her belly and feeling when her abdomen goes rigidly hard. Many queens like to have their favourite human around them during this time, and some even like to have their paw held during contractions! Some queens can get agitated or panicky if their human has to go away, (even to the toilet!) so it is imperative to take time off from work to be around during the week where she is due to give birth.

If the labour has been progressing for several hours, but no kittens are appearing, it is important to take your cues from the queen. If she is becoming agitated and is not settling into her litter box, or she is straining to push but nothing is coming out, it is possible that a kitten is presented the wrong way and needs the attention of a qualified vet to help it out. Only 7% of kittens are still-born, but it is good to have the vet on standby, so that you can rush your queen in for an emergency caesarean if needed. Usually, even breach-presented kittens are born without complications, and the queen will quickly begin to lick it to stimulate it to breathe.

If she is a first-time, inexperienced mum, it may be that she needs a bit of help to kick-start her instinctive behaviour, and a warm towel to dry the kittens as well as clear the mucus from their nose and mouth is useful to have on standby. A pair of sterile, sharp scissors can be used to cut the umbilical cords once the kitten is breathing. The placenta will be delivered shortly after each kitten, and even an inexperienced queen should feel compelled to eat them after each delivery. Each placenta must be checked to ensure that it looks complete, but is often difficult to do so, as the queen can begin to eat it as soon as it appears. It contains high levels of oxytocin which not only helps her to produce milk, but it also triggers her brain to feel trust and love towards her newborns, which helps her to bond with them and want to care for them.

It is important to allow the queen to eat the placentas, so that she can reabsorb important nutrients which help her to bond with and feed her kittens. In case a clumsy queen accidentally nicks one of her kittens whilst cleaning them up after birth, place a bit of placenta on the wound, and it will heal significantly quicker. Just make sure that mum doesn’t try to lick it off too soon! Like with human babies, Mum’s milk is also helpful in case of umbilical cord and other newborn infections: Squeeze a small drop from her teat and drip it into the crusty eye or other infection, and it will soon heal up after a day or so.


We are indebted to the excellent article on Pawpeds called “Embryology of the Domestic Cat, by A.L. Leipoldt, and translated from German into English by Karin Sandbergen.

We also wish to credit the DVD by Pioneer Productions, called: “In the Womb CATS”. It is the program about feline pregnancy in domestic and big cats, which was shown on Channel 4 and the National Geographic Channel. The reconstructed models of in-the-womb cats and lions, and 4-dimensional scan imagery are inspiring!

The copyright of this cat pregnancy calculator belongs to Wychwood Russian Blue Cats.

© Wychwood Russian Blue Cats 2018