I love Harry Potter and I love knowing how my baby was developing while I was pregnant. So with the help of the internet, I put together the Wizard’s Guide to Pregnancy!

In the Wizard’s Guide to Pregnancy, you can compare the size of your baby each week to a wizardly item from the Harry Potter Universe! Does your baby feel like a snitch or a bludger this week?!

8 Weeks

At about 0.6 inches, your baby has doubled in size in the last week! Your baby is the size of a bronze knut. There are 29 knuts in one silver sickle, and 493 knuts in one gold galleon. In 1991, the Daily Prophet cost Hagrid five knuts when delivered by owl. Knuts are worth approximately two cents of US muggle money

9 Weeks

At about 0.9 inches, your baby is beginning to form knees and elbows. Your baby is roughly the size of Marvolo Gaunt’s ring. Of course, you know this signet ring passed through the Peverell family and made its way to Tom Riddle, and contains the resurrection stone! The stone is the only hallow that has the Deathly Hallows symbol etched into it

10 Weeks

Coming in at 1.2 inches, your baby’s ears are forming and the brain is connecting to the spinal cord. Your baby is the size of a snitch! The snitch replaced a rare and protected bird species that was originally used in Quidditch, called the Golden Snidget. The longest game of Quidditch went on for three months because the game doesn’t end until the snitch is caught.

11 Weeks

Your baby’s arms and legs are beginning to function and baby is growing fingernails and nipples. Your baby is 1.6 inches long, and the size of a time turner. Time turners have a limit of traveling back a maximum of five hours, which makes time travel safe for people and the fabric of time. The user might still age while within time produced by the Time Turner.

12 Weeks

Your baby has reached 2.1 inches! In the wizarding world, your baby is the size of Salazar Slytherin’s locket. After the locket became a Horcruz, those in its proximity became irritable and eventually unable to summon enough happiness to use a Patronus Charm. However, someone as awful as Dolores Umbridge is not hindered by the negative magic!

13 Weeks

Week 13 marks the end of the first trimester! Your baby is 2.91 inches and the size of a Remembrall. Would Harry have ever been Gryffindor’s seeker if Malfoy hadn’t stolen Neville’s Remembrall? They’re not very useful objects because you have to “remember what you have forgotten,” as Neville complains.

14 Weeks

Your baby is 3.4 inches long now, which is the size of a box of chocolate frogs. After defeating Voldemort, Harry, Ron, and Hermione were placed on Chocolate Frog cards, which Ron considers his proudest moment. Did you know they also make white chocolate frogs?

15 Weeks

Your baby is approaching four inches in length and their eyes are now developed enough to sense light. Speaking of lights, your baby is now the size of Dumbledore’s creation, the Deluminator. Besides controlling light, it has a mysterious way of guiding its owner to the place they need to be.

16 Weeks

Itty bitty baby ear canal bones are starting to develop, which means your baby can hear the sound of your Harry Potter audiobook. At 4.6 inches, your baby is now approaching the size of the Sorcerer’s Stone (or Philosopher’s Stone, if you prefer). Gilderoy Lockhart would boast as a student that he would create a stone before graduating. Which we know never happened. Or did it? OBLIVIATE!

17 Weeks

At 5.1 inches, your baby has now developed sweat glands and fingerprints! Your baby is the size of Helga Hufflepuff’s cup. This cup is actually the only object known to have been stolen from a vault at Gringotts. The cup is also theorized to have been the very first dining utensil at Hogwarts to assist in the magical transport of the food from the House Elf Kitchens to the Great Hall

18 Weeks

At 5.6 inches, your baby is now the diameter of the lost Diadem of Ravenclaw. The diadem is said to increase the wearer’s intelligence. Tom Riddle transformed it into his fifth Horcrux. Unfortunately, we cannot complete the set of Hogwarts house heirlooms during pregnancy, unless your baby reaches three feet inside the womb to achieve the length of the Sword of Gryffindor!

19 Weeks

At 6.0 inches, your baby has reached the length of a Basilisk fang. Just the fang. Basilisks can grow up to fifty feet and live for a thousand years. Breeding of basilisks was banned in medieval times and there were no recorded sightings of basilisks in over 400 years until the Chamber of Secrets was opened. Basilisk venom has only one known cure -phoenix tears.

20 Weeks

Halfway done! This week, your baby is 10.1 inches long, about the size of a bludger. Thankfully, not the weight, as they are made of iron and weigh 149 pounds. Early bludgers were bewitched rocks that chased players, but they were eventually deemed too fragile as they were smashed by a beater’s bat and results in players being chased by flying gravel for the remainder of the game.

21 Weeks

Your baby is forming eyelids! At 10.5 inches, your baby is the size of Slughorn’s hourglass. The sand runs accordingly with the quality of conversation. If stimulating, the sand runs slowly. Since it is never mentioned in the book, little is known about how or when Horace Slughorn acquired this Slytherin inspired object.

22 Weeks

Your baby’s eyes are maturing and fully formed, but the irises are still uncolored. At 10.9 inches, your baby is the length of a Ministry of Magic interdepartmental memo. As mentioned in the film, the Ministry used to use owls to communicate between departments at the Ministry of Magic. However, it was quite messy as the owls left droppings everywhere.

23 Weeks

Fingernails have been growing since the Time Turner week, but now they cover the entire fingertip. At 11.4 inches, your baby is the size of a baby acromantula. Acromantulas have eight eyes, a taste for human flesh, highly toxic venom, are capable of human speech, and adults are the size of a horse. The babies are “no bigger than a Pekingese!”

24 Weeks

At 11.8 inches, your baby is just about the diameter of a quaffle! Modern quaffles are red and contain gripping charms allowing players to hold onto them. The original ball was brown, not enchanted, and had a leather strap attached to allow players to throw and catch it one handed.

25 Weeks

Your baby is roughly the size of a bottle of Skele-Gro, which is an awful tasting potion used to regrow bones. Malfoy attributes Hagrid’s size to an accidental overdose of Skele-Gro as a child. Did you know that Linfred of Stinchcombe, the 12th century wizard credited with inventing Skele-Gro is the founding patriarch of the Potter family?

26 Weeks

At 14 inches, your baby is the size of Dolores Umbridge’s black quill, a magical torturous object. This quill carves whatever the user writes onto the back of their hand and the blood will be used as ink on the parchment. Continuous use will eventually scar. Dolores Umbridge instructs Harry to use this quill during numerous detentions to write “I must not tell lies.”

27 Weeks 

Your baby is allegedly sleeping for 95% of the day at 14.4 inches, your baby is the size of a ferret, minus the tail. Wait, isn’t this about Harry Potter sizing? Oh, but what about when Barty Crouch Jr, disguised as Alastor Moody, transfigured Malfoy into a white ferret? Is this cheating? Transfiguration is not allowed as a punishment, regardless of how funny the amazing bouncing ferret may be.

28 Weeks

At 14.8 inches, your baby is the size of the “manky old boot” portkey used to transport to the Quidditch World Cup. Almost any inanimate object can be turned into a portkey. Once bewitched, the object will transport anyone who grasps it to a prearranged destination. Portkeys were used to transport students to Hogwarts prior to the creation of the Hogwarts Express.

29 Weeks

At 15.2 inches, your baby is the size of a murtlap. The growth on a murtlap’s back may be pickled and eaten to improve ones resistance to jinxes, although eating an excess may case one to grow purple ear hair. Murtlap essence is what Harry put on his hand to heal the cuts after his detention with Umbridge

30 Weeks

Three quarters of the way there! Your baby is 15.7 inches long, the size of the Marauder’s Map. This magical document cannot be fooled by animagi, polyjuice potions, or invisibility cloaks. The Hogwarts ghost even appear on the map. The only things that do not show up are unplottable rooms, such as the Room of Requirement, the Chamber of Secrets, and any Jr. or Sr. at the end of names.

31 Weeks

Your baby is starting to crowd your lungs at the tail end of your seven months at 16.2 inches. Hagrid’s wand was 16 inches, the longest known wand! It was made of oak with an unknown core. It is speculated that Dumbledore mended the wand before it was concealed.

32 Weeks

At 16.7 inches, your baby is the size of a dragon egg. A Norwegian Ridgeback egg, to be specific! Young ridgebacks develop the ability to shoot flames earlier than other breeds. Females are generally more ferocious than the males. Which brings up the fact that Norbert, the dragon hatched at Hagrid’s hut, was later discovered to be female, and thus renamed Norberta.

33 Weeks

At 17.2 inches, your baby is approximately the length of the Daily Prophet. A Protean harm is used to change the news in each edition over the course of the day. Subscriptions cost 1 knut, and the Daily Prophet has been producing papers since 1743. The paper also features evening and weekend editions, properly called the Evening Prophet, and the Sunday Prophet.

34 Weeks

Your baby is now 50% of the volume of the womb. At 17.7 inches, your baby is the size of a young Mandrake, not including the leaves. Mandrakes not only resemble humans, but also have similar behaviors. Mandrakes become moody and secretive when they reach adolescence, as well as throw loud parties and develop acne.

35 Weeks

All of your baby’s major organs are fully developed and functioning. At 18.2 inches, your baby is the length of a beater’s bat. The design of the bat has not changed much since the 15th century, despite the bludger, snitch, and quaffle all being redesigned. The bats are enchanted to amplify the striking power of the beater – as week twenty informed us, the bludgers are made of iron.

36 Weeks

At 18.7 inches, your baby is the size of the Hogwarts Sorting Hat. It speaks to the wearer in a quiet voice and uses Legilimency to interpret their thoughts. The Hat stubbornly refuses to admit it has made a mistake in its sorting of a student. Before sorting the students each year, the Hat recites a new introductory song, which we do not get to hear in the films.

37 Weeks

Your baby is 19.1 inches long, and now at full term! Baby is the size of Crookshanks this week. Crookshanks is Hermione’s cat, who is also half kneazle. They are very intelligent, independent, and have an uncanny ability to detect suspicious and distrustful people. Harry’s neighbor, Arabella Figg, makes her living breeding kneazles.

38 Weeks

Each passing day, your baby’s lungs and liver are getting stronger. At 19.6 inches, your baby is the length of a hippogriff feather. Half horse and half eagle, these creatures are immensely proud and very dangerous. Newt Scamander’s mother was a known hippogriff breeder. When breeding, hippogriffs build nests on the ground and lay only a single egg. The egg will hatch within 24 hours.

39 Weeks

At 19.9 inches, your baby is the length of the Triwizard Cup. The cup was made in 1294, when the first Triwizard Tournament took place. Since then, the Cup has been held by the victorious school until the following tournament, which was held every 5 years until its discontinuation in 1792.


Thanks for reading A Wizard’s Guide to Pregnancy! Have ideas for other articles like this? I had a lot of fun writing this and would love to do something similar for another nerdy topic.

And check out some of my other Harry Potter-related stuff. Like wizardly pregnancy announcements.

Or magically nerdy baby onesies.

Or a subtle reference to Harry Potter with a nerdy baby name!

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