Australian data regarding spontaneous conceptions following a live birth conceived by assisted reproductive technologies (ART) have not yet been reported.

This study aimed to determine the incidence of spontaneous conceptions within 18–24 months after women had a first infant conceived by ART (ARTC) or spontaneously conceived (SC). Factors associated with spontaneous pregnancies in women with ARTC first infants were investigated.

Materials and Methods
Nulliparous women were recruited through ART clinics (n = 297) and maternity hospitals (n = 295) in Melbourne and Sydney, Australia. Participants were interviewed in pregnancy and when their first infants were aged 18–24 months. Information was collected on pregnancies since the first infant’s birth. The outcome was any subsequent conception during this period.

Follow‐up data were available for 198 women with SC first infants and 236 women with ARTC first infants, 94 (40%) of whom had further ART following the first birth. Spontaneous conceptions had occurred in 40% of women with SC first infants and 33% of women with ARTC first infants who had not had subsequent ART. Twenty‐four per cent of pregnancies after the birth of SC first infants were unexpected, compared with 61% of subsequent pregnancies (without further treatment) after the birth of ARTC first infants (P < 0.001). Subsequent, spontaneous pregnancies in women with ARTC first infants were significantly associated with unexplained infertility and shorter partner relationship duration. Discussion Discussion about contraception is recommended if women with ARTC first infants do not wish to have more children or wish to delay subsequent pregnancies.