How are fingerprints formed before birth?
Quick Answer
Fingerprint patterns form in the womb, mainly between weeks 10 and 24 of pregnancy. The final ridges are shaped by both genes and tiny differences in pressure, growth, and movement in the uterus.
The Full Story
Fingerprint ridges begin forming during fetal development and are usually set by about the 24th week of pregnancy. Genes help determine the overall pattern, but the exact details are influenced by local conditions in the womb, which is why identical twins have similar but not identical fingerprints. The basic ridge pattern is permanent because it is built into the deep layers of the skin as the fetus grows. That is also why fingerprints can remain stable for life unless the skin is severely damaged.
Key Facts
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"Your fingerprints start forming before you’re even born—here’s how."