Objective: To evaluate the contribution of different subfertility treatments to the number of multiple pregnancies in a subfertile population.
Design: A prospective cohort study between January 2002 and December 2006.
Setting: A subfertility clinic in a large regional training hospital in the Netherlands.
Population: A total of 1,001 continuing pregnancies, of which 63 (6.3%) were multiple.
Methods: Of all pregnancies, mode of conception, outcome and type of pregnancy (singleton or multiple) were documented.
Main outcome measures: Proportions of continuing and multiple pregnancies caused by the different modes of conception.
Results: Of all subfertility related continuing pregnancies, 46% were conceived spontaneously, 16% were induced by clomiphene citrate (CC), 2.4% by follicle stimulating hormone (FSH) and 14% by intra-uterine insemination combined with controlled hyperstimulation (IUI/(COH)). In vitro fertilization (IVF) and its related techniques resulted in about a fifth of all continuing pregnancies (n = 212), but were responsible for more than half (n = 36) of the multiple pregnancies. Furthermore, 18% of the multiple pregnancies were induced by IUI/(COH), 3% by FSH, 11% by CC, whereas about 11% were conceived spontaneously.
Conclusions: IVF and intra-cytoplasmic sperm injection (ICSI) were responsible for the majority of the multiple pregnancies in a subfertile population. Therefore, twin prevention should be focused on further promoting elective single embryo transfer (eSET). Fertility treatment and particular IVF should not be started as long as the spontaneous pregnancy prognosis is good.