Monique and Stephen's twins were conceived via IVF. Her twins were identified as dichorionic/diamniotic at 14 weeks gestation. She received regular antenatal care from an experienced obstetrician and decided to stop work at 28 weeks gestation. Her BP remained within normal limits until 35 weeks gestation when a slight increase was noted. Monique and Stephen attended prenatal classes and she is planning on a vaginal birth. At 36 weeks it was noted that Twin B's growth had slowed, therefore induction of labour was suggested by the physician. After reviewing the risks and benefits with their physician, Monique consented to this plan of care. What is the method of conception used by Monique and Stephen for their twins?
1) Natural conception
2) Intrauterine insemination
3) In vitro fertilization
4) Surrogacy