By Sarina Gomez
This article is general information, not medical advice. Ask your midwife, OB-GYN or sonographer about your own pregnancy and scans.
Neither Ramzi theory nor skull theory has been shown to work. Ramzi theory comes from a single article that was never published in a peer-reviewed journal and has not been confirmed by any later study, and skull theory has no published study at all. If you want an early answer with evidence behind it, a cell-free DNA blood test or a sonographer’s read of the nub from 12–13 weeks are the options that have been tested.
Ramzi theory: the claim and where it came from
Ramzi theory says the side of the uterus where the placenta forms at about 6 weeks gives away the sex: placenta on the right means a boy, on the left means a girl. It is named after the author of the article “The Relationship Between Placental Location and Fetal Gender (Ramzi’s Method)” appeared on the Contemporary OB/GYN website in 2011.
Three things about that origin matter:
- It wasn’t peer reviewed. The article ran on a professional news website, not in a journal where other experts check the method before publication.
- The publisher has since added a caveat. Contemporary OB/GYN replaced the page with an editor’s note in October 2020 stating that “Ramzi’s method has not been confirmed in any additional studies” and that “many ob/gyns dismiss the validity of Ramzi’s method entirely” (Contemporary OB/GYN).
- The high accuracy figures quoted online trace back to that one article. You’ll see them repeated on forums and in apps, but no independent team has reproduced them in a published paper.
What the peer-reviewed evidence says about Ramzi
The peer-reviewed evidence is close to empty, and that is the main finding. No independent team has confirmed Ramzi’s left-right rule in a major peer-reviewed journal. The closest thing in a major journal is a 2010 poster abstract, “The role of placental location assessment in the prediction of fetal gender,” printed in a congress supplement of Ultrasound in Obstetrics & Gynecology (The and Chan, 2010). A short congress abstract isn’t a full, peer-reviewed study either, so it can’t settle the question in either direction.
The biology also argues for caution. The editor’s note on the Ramzi page points out that there are no outward signs of sex until about 9 weeks, and that the genitals can’t be seen clearly until about 15 weeks (Contemporary OB/GYN). A 6-week scan is looking at a pregnancy where none of that is visible yet.
Why reading Ramzi at home goes wrong
Even if the theory were sound, applying it to your own scan photo adds new ways to be wrong:
- Left and right are hard to read. Whether the left of the image is your left depends on the type of scan, the probe position and the machine’s display settings. Online guides add their own “flip the image if…” rules, and they don’t agree.
- Early scans are small. At 6 weeks, the gestational sac fills only a small part of the image, and the start of the placenta isn’t labeled.
- Many parents don’t have a 6-week scan at all. ACOG notes that a first-trimester ultrasound is not standard (ACOG, ultrasound exams), so the “Ramzi photo” is often a later scan where the placenta’s position tells you even less.
Skull theory: no study at all
Skull theory says a boy’s skull looks blockier on the 12-week scan, with a squarer jaw and a heavier brow, while a girl’s looks rounder with a smaller chin. It circulates in online pregnancy forums and has never been tested: no peer-reviewed study of it turns up in PubMed.
The practical problems are the same as with Ramzi. A 12-week profile is small, grainy and taken from whatever angle the baby allowed, and tilt alone changes how square a jaw looks on paper. When a skull-theory guess turns out right, there was a 50% chance it would. Our guide to 3D ultrasound vs the real baby explains why even later, clearer scans make faces look different from the newborn.
Ramzi, skull and nub theory side by side
Of the three early-scan theories, only nub theory has been studied, and it works only from about 12–13 weeks in a trained sonographer’s hands.
| Theory | Week | What’s read | Peer-reviewed evidence |
|---|---|---|---|
| Ramzi | About 6 | Side of the placenta | Not confirmed by any published study |
| Skull | About 12 | Skull and jaw shape | None |
| Nub | 12–14 | Angle of the genital tubercle | Several studies; about 92% at 12 weeks and 98–100% from 13 weeks when a sonographer measures it (Hsiao et al., 2008; Efrat et al., 2006) |
The details, including why 11 weeks is so unreliable, are in our nub theory guide.
A guess that says it’s a guess
If you’re keeping the sex a surprise, or you just don’t know yet, a guess can still be part of the fun as long as nobody mistakes it for an answer. That’s how the SeeMyBaby gender reveal party works. You pull the ribbon on a gift box, and after you buy the gender add-on on the paywall, the box opens on a drumroll with pink or blue balloons and confetti. The result is a playful AI guess, just for fun, not a medical result, and SeeMyBaby doesn’t read the placenta or the skull. Parents who already know the sex tell the app, and no guess is made.
For a real answer, ACOG notes that a cell-free DNA blood screen can be done from 10 weeks and looks at the sex chromosomes (ACOG, prenatal genetic screening tests), and that the standard ultrasound at 18–22 weeks may show the sex if the baby is in a good position (ACOG, ultrasound exams). See when can you find out the gender for the full timeline, the boy or girl old wives’ tales for the folklore, and whether any gender predictor is 100 percent accurate. More guides are on the SeeMyBaby blog.
Sources
- Contemporary OB/GYN. The relationship between placental location and fetal gender (Ramzi’s method), 2011, with editor’s note of October 2020.
- The S, Chan L. P18.17: The role of placental location assessment in the prediction of fetal gender. Ultrasound in Obstetrics & Gynecology, 2010; 36(S1): 242 (congress abstract).
- Efrat Z et al. Fetal gender assignment by first-trimester ultrasound. Ultrasound in Obstetrics & Gynecology, 2006.
- Hsiao CH et al. Fetal gender screening by ultrasound at 11 to 13+6 weeks. Acta Obstetricia et Gynecologica Scandinavica, 2008.
- ACOG. Prenatal genetic screening tests and Ultrasound exams.
Questions parents ask
How accurate is Ramzi theory?
No one knows, because it has never been confirmed in a peer-reviewed study. The accuracy figures quoted online come from the original 2011 article, which wasn’t peer reviewed.
Does a placenta on the right mean a boy?
There’s no published evidence that it does. Reading left and right on a scan photo is also unreliable, because it depends on how the scan was taken and displayed.
Is skull theory accurate at 12 weeks?
It has never been studied. Any correct skull-theory guess has the same 50% chance as a coin toss.
What is the most accurate early way to find out the sex?
A cell-free DNA blood screen, which ACOG says can be done from 10 weeks and looks at the sex chromosomes. On ultrasound, a sonographer’s read of the nub from 13 weeks has the best published accuracy.
