Beyond the uterine first pass: optimizing programmed frozen embryo transfers. A mini-review.

With the greatly increased popularity of segmented in vitro fertilization and frozen embryo transfers, progesterone replacement strategies in programmed cycles are being reexamined. Bidirectionality and the limited capacity of the uterine first pass provide an explanation for disconnects between the endometrial and serum levels when either vaginal or intramuscular progesterone is used alone. Whereas monotherapy departs from the physiology of spontaneous pregnancies, combined therapy provides physiologic replacement while minimizing the number of injections.

Individualised luteal phase support in artificially prepared frozen embryo transfer cycles based on serum progesterone levels: a prospective cohort study.

Study Question: Does an individualised luteal phase support (iLPS), according to serum progesterone (P4) level the day prior to euploid frozen embryo transfer (FET), improve pregnancy outcomes when started on the day previous to embryo transfer?

Summary Answer: Patients with low serum P4 the day prior to euploid FET can benefit from the addition of daily subcutaneous P4 injections (Psc), when started the day prior to FET, and achieve similar reproductive outcomes compared to those with initial adequate P4 levels.

What Is Known Already: The ratio between FET/IVF has spectacularly increased in the last years mainly thanks to the pursuit of an ovarian hyperstimulation syndrome free clinic and the development of preimplantation genetic testing (PGT). There is currently a big concern regarding the endometrial preparation for FET, especially in relation to serum P4 levels around the time of embryo transfer.

Low progesterone levels on the day before natural cycle frozen embryo transfer are negatively associated with live birth rates.

Study Question: Are progesterone (P) levels on the day before natural cycle frozen embryo transfer (NC-FET) associated with live birth rate (LBR)?

Summary Answer: Regular ovulatory women undergoing NC-FET with serum P levels <10 ng/ml on the day before blastocyst transfer have a significantly lower LBR than those with serum P levels >10 ng/ml.

What Is Known Already: The importance of serum P levels around the time of embryo transfer in patients undergoing FET under artificial endometrial preparation has been well established. However, no study has analyzed the importance of serum P levels in patients undergoing FET under a true natural endometrial preparation cycle.

Factors associated with serum progesterone concentrations the day before cryopreserved embryo transfer in artificial cycles.

Research Question: What factors determine serum progesterone concentrations the day before cryopreserved embryo transfer in artificially prepared cycles?

Design: Retrospective cohort study at a university-affiliated fertility centre including infertile women under 45 years old using own oocytes who underwent a total of 685 single cryopreserved blastocyst transfers under hormonal therapy. Determinants that affected live birth rate (LBR) were analysed using a multivariate logistic regression. Univariate analysis and multivariate linear regression were used to evaluate independent factors that affect serum progesterone concentrations.

Reproductive outcomes in recipients are not associated with oocyte donor body mass index up to 28 kg/m: a cohort study of 2722 cycles.

The effect of increasing donor body mass index (BMI) on clinical pregnancies was retrospectively analysed in a cohort of consecutive 2722 donor oocyte IVF cycles. The relationship between donor BMI and clinical pregnancies was assessed after adjusting for recipient BMI. Clinical pregnancy rates and live birth rates (LBR) were no different with increasing donor BMI (up to donor BMI ≤28 kg/m).