Objectives: To understand differences between birth expectations and experiences, and to explore possible reasons for mismatches. Design: Online survey Setting: UK Population: Postnatal primiparous (PP) and multiparous (MP) women within 5 years of a birth Methods: Survey advertised on social media, Participants completed questions relating to birth expectations, experience and preparedness. Data were analysed descriptively and presented overall and by parity. Results: Of the 819 women, 40% expected birth to be straightforward [PP 29% vs MP 51%], 20% anticipated difficulty [PP 22% vs MP 19%], and 40% [PP 51% vs MP 30%] were unsure. Among the 737/819 whose birth was not exactly as expected, 44% [PP 30% vs MP 47%] found it better than expected, while 56% [PP 66% vs MP 38%] found it more difficult. Unplanned births were higher in those with difficult experiences, particularly for primiparous women [PP 58% vs MP 23%]. Women cited quicker births, fewer complications, and better coping as reasons for positive experiences, while complications, pain, and slower labour contributed to difficulties. Overall, 77% (633/819) [PP 64% vs MP 80%] of women felt very or somewhat prepared for birth. Among them, 76% (484/633) [PP 88% vs MP 69%] had attended antenatal education. However similarly, 75% (130/174) [PP 80% vs MP 66%] of those who felt less prepared had also attended antenatal education. Conclusions: Most women have an element of expectation-experience mismatch. Over half in the found birth more difficult than expected, this suggests current approaches to birth preparation may be inadequate. Further research into reducing the expectations-experience gap is needed.