Stillbirth among singletons and twins by mode of conception.

Odds ratios account for clustering within mother, and are adjusted for maternal age, parity, baby's sex and whether twins same-sex.
IF DX: Births to women who had a recorded diagnosis of infertility but no assisted conception treatment from a specialist clinic.
IF TX: Births as a result of spontaneous conception in women with a previous birth from assisted conception.
Singletons and twins combined because of small numbers.
# Significant difference between effect for singletons and twins.