A family history of twinning in relation to multiple implantation

BACKGROUND: A familial basis for dizygotic twinning is known for multiple ovulation. However, for multiple implantation this remains unclear. In IVF/intracytoplasmic sperm injection (ICSI) ‘multiple ovulation’ is artificially induced. If multiple implantation is not hereditary, the incidences of twins in families of patients with single and multiple implantation after IVF/ICSI with double embryo transfer (DET) should be comparable. METHODS: A questionnaire study was conducted among patients with intra uterine pregnancy at 6 weeks of gestation, after IVF/ ICSI treatment with DET 3 days after oocyte retrieval. RESULTS: There were 940 patients who gave their informed consent. For women with single implantation (Group A), the incidence of one and of multiple twins among the family was 27.2 and 15.5%, respectively. For women with multiple implantation (Group B), this incidence was 29.5 and 17.8%, respectively, P 5 0.424. The incidence of one and of multiple twins among first degree relatives was 10.6 and 1.1% in Group A; for Group B this was 8.7 and 1.9%, P 5 0.469. Multivariate regression analysis also did not reveal ‘twins in family’ or ‘twins in first degree’ as an associated variable for multiple implantation at 6 weeks. CONCLUSIONS: Incidences of twins in families of patients with single implantation and patients with multiple implantation after IVF/ICSI are comparable. Our data do not support the concept that multiple implantation is hereditary.