Singleton and twin confinements associated with infertility treatments.

A cross-sectional sample of 150 singleton and 159 twin confinements delivered in Western Australia in 1991 were randomly sampled in 1993; 63% of the women responded to a postal questionnaire. Thirteen percent of respondents with singletons and 26% of those with twins reported having problems conceiving at some stage in their life. Six percent of those who had singleton confinements and 22% of those women who had twin confinements sought fertility advice prior to the conception of the index pregnancy. One percent (95% CI 0.03%, 5.5%) of women with singletons received infertility treatment compared with 17% (95% CI 10.4%, 26.3%) of those with twins. Overall 82.7% (95% CI 75.2%, 90.1%) of twin confinements followed spontaneous conception, 11.2% (95% CI 5.7%, 19.2%) followed ovarian stimulation treatment alone and 6.1% (95% CI 2.3%, 12.9%) followed IVF or GIFT procedures. The probability of a spontaneous twin confinement was 1 in 95. It was concluded that nearly twice as many twin pregnancies were associated with ovarian stimulation treatment given alone than with IVF and GIFT combined. The routinely collected data about assisted twin conceptions provide an incomplete picture with regard to the role of different infertility treatment modalities.