INSIDEEMBRYO · FERTILITY GLOSSARY
A pronucleus is a temporary haploid nuclear structure containing either the maternal or paternal genome following fertilisation and before the first embryonic mitosis. The female pronucleus develops after completion of oocyte meiosis II, while the male pronucleus forms following decondensation…
A pronucleus is a temporary haploid nuclear structure containing either the maternal or paternal genome following fertilisation and before the first embryonic mitosis. The female pronucleus develops after completion of oocyte meiosis II, while the male pronucleus forms following decondensation and reorganisation of sperm chromatin. During normal fertilisation, one maternal and one paternal pronucleus are typically visible within the fertilised oocyte. Observation of two pronuclei, commonly recorded as 2PN, is the classical morphological indicator of normal fertilisation during IVF laboratory assessment. The pronuclear envelopes subsequently break down as the parental chromosomes organise on the first mitotic spindle before cleavage.
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