Does cleavage- versus blastocyst-stage embryo transfer improve fertility rates in women over 38 years of age undergoing assisted reproductive technology?

Objective: To evaluate whether extending embryo culture to day 5 (D5) affects pregnancy rates in women older than 38 years undergoing in vitro fertilization (IVF). Methods: This retrospective, observational cohort study included data from fresh IVF cycles of women over 38 years, during 2011–2021. The cohort was divided according to day 3 (D3) versus D5 embryo transfer (ET). Results: A total of 346 patients (ages 38–45 years) who underwent 496 IVF cycles were included, each yielding one to six embryos. A total of 374 (75%) fresh D3 ETs were compared with 122 (25%) D5 ETs. Demographically, there were more nulliparas in the D3 group (189 [50.9%] vs 47 [38.8%], P = 0.021). Higher gonadotropin dosage was used (3512 ± 1346 vs 3233 ± 1212 IU, P = 0.045) and lower maximum estradiol levels were reached in the D3 group (1129 ± 685 vs 1432 ± 708 pg/mL, P = 0.002). Thirty-three (27%) of the D5 cycles resulted in transfer cancelation due to failure of blastocyst formation (P = 0.001). However, clinical pregnancy rates (P = 0.958), live birth rates (P = 0.988), and miscarriage rates (P = 0.710) did not differ between D3 and D5 ETs. Multivariable logistic regression for clinical pregnancy rate showed that day of transfer did not have a significant effect on the odds (P = 0.376), but maternal age (P = 0.001) and number of retrieved oocytes (P = 0.009) were significant variables. Conclusions: In older women, culturing embryos to blastocyst stage can decrease invalid ETs without reducing pregnancy rates. Cancelation rates are higher but it may avoid interventions and conserve valuable time.