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Home > Pet rats > How Long Are Pet Rats Pregnant? Vet Approved Facts & Info

How Long Are Pet Rats Pregnant? Vet Approved Facts & Info

White-grey pregnant rat in a cage

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Dr. Luqman Javed

Veterinarian, DVM

The information is current and up-to-date in accordance with the latest veterinarian research.

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Pet rats are part of the rodent family and are very prolific breeders. A female pet rat is only pregnant for around 21 to 23 days, after which she will give birth to a litter of up to 18 pups! The short gestation period and larger litter mean more offspring are likely to survive and carry on the parent’s genes, which is a vital part of survival in the animal kingdom.

Rats breed year-round and are polyestrous; they spontaneously ovulate and don’t have a set ovulation cycle. Usually, rats will mate at night, and male rats are attracted to the female by her scent and mating behaviors. Rats are sexually mature at around 5 weeks old, so some owners may find themselves with more rats than they bargained for if they have a male and female together!

Knowing how rats reproduce and what to expect if you have a litter is important since even accidental litters need the correct care to ensure they’re happy and healthy.


What Is a Pet Rat’s Reproductive Cycle?

Rats follow the same reproductive cycle as most animals, with a few key differences.

Female rats are spontaneous ovulators, and a female rat will release eggs to be fertilized if mated with a male. In addition, a female rat who has just given birth and mates with a male may release eggs as a reflex to the mating action to conceive again. In such an instance, they’re termed as reflexive ovulators. These two methods of ovulation are part of the reason why rats are very successful at procreation.

There are four stages to the rat ovulation cycle: proestrus, estrus, metestrus, and diestrus. The cycle is rapid and only takes 4 to 5 days to complete.

happy white rat on shoulder
Image By: Darina Matasova, Shutterstock


The proestrus phase is the first phase of the estrous cycle and is essentially a period where a female rat’s body is preparing for both ovulation and eventual copulation. Females are not receptive towards males in this phase. During this phase, the vulva is often gaping and the visible tissues of the vagina are moist and reddish-pink in color. This phase lasts around 14 hours.


Female rats in estrus present to males by pushing their hind ends in the air. They vibrate, sway their heads, and become very still when touched. This is the phase in which eggs are released from the female’s ovaries to be fertilized by the male’s sperm. The fertilized eggs will then implant into the uterus, and pregnancy will begin. During this phase, the vulva appears similar to that seen during proestrus. However, the visible tissues are usually lighter pink and less moist and may have some visible stripes. This phase lasts around 24-48 hours.

Metestrus and Diestrus

The last two phases of ovulation, metestrus and diestrus, occur if mating does not occur and the female doesn’t get pregnant. During metestrus, the body essentially “cools down” from the estrous cycle, and the levels of hormones decrease.

There are no behavioral changes in females at this stage, and the genitals shrink to their normal size and color. The vulva appears pale and dry. There may also be a semen plug visible if mating occurs (however, the presence of the plug isn’t a guarantee of pregnancy). During diestrus, the body resets and prepares for a new cycle. Metestrus lasts 6 to 8 hours, and diestrus lasts 48 to 72 hours before the process begins again. If the rat is pregnant though, diestrus will last the entire duration of the pregnancy.

divider-rodent How Can I Tell if My Rat Is Pregnant?

There are some subtle and not-so-subtle signs that a rat is pregnant, with the more obvious ones occurring later in the pregnancy. Because the rat gestation period is short (21 to 23 days), pregnancy sigma can develop almost suddenly if you weren’t aware your rats had mated.

The early signs of pregnancy can be difficult to spot, but looking closely and observing behavior can help you determine whether or not your doe is pregnant.

Signs a female rat (doe) is pregnant include:

  • A mucus plug in the vagina after mating (only present for a few days)
  • Weight gain
  • Eating and drinking more
  • Visible swelling of the belly (particularly at the sides)
  • More visible nipples
  • Nest making
Pregnant rat and human hand on a pink background
Image By: Maryia Karneyenka, Shutterstock


Sometimes, if neutered males mate with them, rats can go through a pseudopregnancy. This is usually shorter than normal pregnancy, around 17 days, and will involve nest-making and potentially eating and drinking more. Your rat should come out of pseudopregnancy without any issues; if you have any concerns about behavioral changes, speak to your vet.

When Will I Know My Rat Is Going Into Labor?

There are a few signs you can look out for that indicate your rat will give birth soon, which usually begins a few days beforehand. The first sign is nest making; like many animals, your rat will make a comfortable nest to give birth and nurse her babies. Provide her with lots of nesting material so she can construct her nest to her liking, but make sure not to use wood shavings or stringy, fibrous bedding.

A few days before birth, the swelling in your rat’s abdomen will drop from the sides of her belly to underneath as her body prepares her for labor. Once her abdomen spasms and moves, she will enter labor and begin having her babies.

The labor is usually swift, taking around 2 hours to birth a litter. Your rat’s abdomen will contract very noticeably, and she will stretch out, often sitting back on her haunches and licking her genitals as the baby comes out. Rat pups can be born head or tail first and are pink, blind, and hairless!

How Do I Care for My Pregnant Rat and Her Babies?

Pregnant rats need proper nutrition and care to stay healthy and raise their babies correctly. When you discover your rat is pregnant, taking them to the vet for an exam can ensure they’re doing okay and give you a guideline on how far along they are. Your vet can feel your rat’s abdomen to see how many babies she has, but this is usually only accurate when she’s nearing labor.

Separating your rat from other rats when she’s nearing the end of her pregnancy and making sure she doesn’t do anything too strenuous, such as high climbing, is essential, as she can easily hurt herself. When she’s giving birth, keep an eye on her and her babies but don’t interfere. She will clean off each pup as they are born and eat the placentas as they are delivered.If any babies are born dead, the mom may eat them. This is considered normal and you shouldn’t attempt to remove the baby, as you may stress out the mother.

Make sure to keep mom away from any males since rats can get pregnant immediately after giving birth! Once she has birthed all her litter, look at them to ensure they’re all feeding and healthy. Baby rats are born deaf, blind, hairless, and utterly dependent on their mother.

They are bright pink and active and should have a white line running along their lower belly; this line shows that their stomach is full of nutritious milk. Your rat won’t eat much in the first days following birth, so feeding her a healthy meal is vital. She’ll also need to stay hydrated as she feeds her pups.

mother rat feeding its children
Image By: Liukov, Shutterstock

How Can I Make Sure My Rat Doesn’t Get Pregnant?

The best way to ensure rats don’t get pregnant is to separate males and females once they reach sexual maturity at around 5 weeks. This is easier said than done, as rats are very social animals that must be kept in groups. Getting the males neutered is the next best thing.

Castrating males is easier than spaying female rats, and the procedure is less risky. If you are unsure about the sexes of your rats, separate them and take them to your vet’s office for help on sexing them correctly and guidance on when to have the males neutered.



Since rats are rodents, they can reproduce very quickly. Rats have a short gestation period of 21 to 23 days and can have as many as 18 babies per litter. Therefore, separating male and female rats that haven’t been neutered is important to prevent pregnancy. Females who have given birth can become pregnant again immediately afterward, so keeping pregnant and lactating mothers away from the males is also very important!

Featured Image Credit: sakavichanka, Shutterstock

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