Maternal Cardiovascular Adaption to Pregnancy in IVF Patients Following Frozen Embryo Transfer (FET)

Inclusion Criteria: * Autologous embryo transfer in programmed FET-cycle or modified-natural FET-cycle or * Planned donor egg transfer in programmed FET-cycle or modified-natural FET-cycle * Age \< 40 years * BMI \< 35 * Primary diagnosis being unexplained infertility, male infertility or tubal factor * Singleton blastocyst transfer Exclusion Criteria: * PCOS * Essential hypertension * Diabetes Mellitus (type 1 or 2) * Known cardiac disease * Antiphospholipid syndrome, Lupus erythematosus, rheumatoid disease * Preelampsia, gestational hypertension, gestational diabetes or severe intrauterine growth restriction (IUGR) in any previous pregnancy * Smoking * Multiple pregnancy * Severe claustrophobia or any other contraindications to MRI