Background Short interpregnancy intervals (IPIs) are associated with adverse obstetric outcomes. However, few studies have explored women’s understanding of ideal IPIs or investigated knowledge of the consequences of short IPIs.

Methods We performed a prospective questionnaire-based study at two hospitals in Sydney, Australia. We recruited women attending antenatal clinics and collected demographic data, actual IPI, ideal IPI, contraceptive use, and education provided on birth-spacing and contraception following a previous live birth. We explored associations between an IPI <12 months and a selection of demographic and health variables.

Results Data were collected from 467 women, of whom 344 were pregnant following a live birth. Overall, 72 (20.9%) women had an IPI <12 months only 7.5% of whom believed this was ideal, and the remaining stating their ideal IPI was over 12 months (52.3%) or they had no ideal IPI (40.3%). IPI <12 months following a live birth was significantly associated with younger age (p=0.043) but not with ethnicity, relationship status, education, religion, parity nor previous mode of delivery. IPI <12 months was associated with non-use of long-acting reversible contraception (LARC) (p<0.001), breastfeeding <12 months (p=0.041) and shorter ideal IPI (p=0.03). Less than half of the women (43.3%, n=149) reported having received advice about IPI and less than half about postnatal contraception (44.2%, n=147).

Conclusions Younger age and non-use of LARC are significantly associated with IPIs <12 months. A minority of women with a short IPI perceived it to be ideal. Prevention of short IPIs could be achieved with improved access to postnatal contraception.