Obstetrical Outcomes of Fresh in vitro Fertilization Cycles after Embryo Transfer at Different Stages of Early Embryonic Development

Introduction:

Clinical pregnancy rate and live birth rate are increased with blastocyst stage ET compared to cleavage stage. Conflicting data regarding the association between embryo age at transfer and obstetrical outcomes.

Aim:

To assess differences in obstetrical outcomes of pregnancies following Day 2, Day 3 and Days 5/6 fresh embryo transfer (ET)

Materials and methods:

A retrospective cohort study including all pregnancies following fresh IVF/ intra-cytoplasmic sperm injection (ICSI) ET cycles performed between January 2014 and December 2015 at Fertility and In Vitro Fertilization Unit of the tertiary Soroka University Medical Center was conducted. The study groups consisted 48, 72, 120 and 144 hours embryos. Pregnancies were confirmed by a serum beta human chorionic gonadotropin measurement. Data was collected from patients` medical records and IVF Laboratory database. Multiple regression models were constructed to control for confounders.

Results:

A total of 534 pregnancies following fresh IVF/ICSI ET on Day 2 (n=189, 35.4%), Day 3 (n=200, 37.5%), and Days 5 or 6 (n=145, 27.2%) were included. Live birth rate demonstrated a linear association to developmental stage at ET with highest rates in bladtocysts and gradually lower in Day 3 and Day 2 ET (79.2%, 65.8% and 60.6% respectively, p =0.001). Multivariate logistic regression revealed that increased maternal age was negatively associated with live birth (odds ratio (OR) =0.94 , 95% confidence interval (CI) = 0.90-0.98, p=0.004).

A positive linear association was observed between ET age and clinical pregnancy rate (77.3%, 87.5% and 90.3% for Days 2, 3 and 5/6 respectively, p =0.002), and pregnancy complication rate (29%, 37.3% and 43.3%, p =0.026). Gestational age at delivery (37.87±2.99, 38.03±2.51 and 37.88±2.26 for Days 2, 3 and 5/6 respectively; p= 0.857), low birth rate (18.9%, 17.1% and 21.2%; p=0.710) and congenital anomalies (21.2%, 17.7% and 23.2%; p=0.557) were comparable between the groups

Conclusions:

The commonly approach of blastocyst transfer, as a high quality of embryo has not proven beneficial in terms of live birth rate. Cleavage stage embryos were not associated with adverse perinatal outcome.