Baby Gender Prediction at 13 Weeks
At 13 weeks, you're at the end of your first trimester and early gender prediction is reliable enough to be meaningful. The nub is clearly visible, the skull shows definitive shape differences, and AI accuracy is climbing toward 85%.
Your Baby at 13 Weeks
- ✦Baby is about 65mm — the size of a peach
- ✦Fingerprints are forming on the tiny fingertips
- ✦Baby can now suck their thumb
Gender Prediction Methods at 13 Weeks
Nub Theory
13 weeks is excellent for nub theory. The genital tubercle is clearly differentiated — a steep upward angle for boys, horizontal or slightly downward for girls. Accuracy is around 80%.
Skull Theory
Skull theory is highly readable at 13 weeks. The differences in forehead slope and brow ridge are more pronounced, giving around 75% accuracy.
Chinese Gender Calendar
The Chinese Gender Calendar can be used alongside other methods for an added data point — though ultrasound-based methods are significantly more accurate.
AI Ultrasound Analysis
AI analysis at 13 weeks reaches around 80-85% accuracy by combining nub angle, skull morphology, and other anatomical signals. This is a strong window for predictions.
Get Your AI Gender Prediction
Upload your 13-week scan — our AI combines nub theory and skull analysis for an 80-85% accurate early gender prediction.
Upload Your 13-Week Scan →Frequently Asked Questions
Can you tell the gender of a baby at 13 weeks?
Absolutely — 13 weeks is an excellent time for early gender prediction. Most gender specialists and sonographers are confident making predictions at this stage.
How accurate is gender prediction at 13 weeks?
Around 80% for nub theory, 75% for skull theory, and 80-85% for combined AI analysis. Confidence is high at 13 weeks — this is the most reliable first-trimester window.
What does a boy/girl look like on an ultrasound at 13 weeks?
At 13 weeks, the genitalia are becoming more distinct. Boys show a clearly angled nub and slight scrotal tissue forming; girls show a forked or horizontal nub. The skull shape differences are also more pronounced.