• Wed. Apr 17th, 2024

How Long Are Pet Rats Pregnant? (Rat Gestation Period)


Apr 13, 2023
White-grey pregnant rat in a cage


White-grey pregnant rat in a cage

Pet rats or fancy rats are different shapes, sizes, and shades of brown rats (Rattus norvegicus). 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 eight and 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. Rats are reflex ovulators, and a female rat will release eggs to be fertilized if mated with a male. There are four stages to the rat ovulation cycle: proestrus, estrus, metestrus, and diestrus. It’s good to know roughly when these phases are, so you can gauge how far along your rat might be in pregnancy. The cycle is rapid and only takes 4 to 5 days to complete.

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


The proestrus phase is before ovulation occurs when a female rat is ready to reproduce. Her behavior in this phase is usually the best indicator that she’s ready to mate, and there will also be a few physical changes.

Female rats in proestrus present to males by pushing their hind ends in the air. They vibrate, sway their heads, and become very still when touched. They’ll also have swollen genitals that can seem alarming at first glance, but that is normal. This phase lasts around 14 hours.


This is the phase in which eggs are released from the female’s ovaries to be fertilized by the male’s sperm. There aren’t many differences in normal behavior during estrus, except the female will no longer present herself to the male. The fertilized eggs will then implant into the uterus, and pregnancy will begin. 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 menstrual 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. During diestrus, the body re-sets and prepares for a new cycle. Metestrus lasts 6 to 8 hours, and diestrus lasts 48 to 72 hours before the process begins again.

divider-rodentHow 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 Credit: 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 kittens (or 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 kit as they are born and eat the placentas as they are delivered. If any babies are born dead, move them away from mom as she may eat them (this is a natural behavior).

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 kits.

mother rat feeding its children
Image Credit: 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.


Final Thoughts

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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