Oocyte Scoring Enhances Embryo-Scoring in Predicting Pregnancy Chances with IVF Where It Counts Most

PLoS One. 2015 Dec 2;10(12):e0143632. doi: 10.1371/journal.pone.0143632. eCollection 2015.


Context: Our center's quality improvement optimization process on many occasions anecdotally suggested that oocyte assessments might enhance embryo assessment in predicting pregnancy chances with in vitro fertilization (IVF).

Objective: To prospectively compare a morphologic oocyte grading system to standard day-3 morphologic embryo assessment.

Design, setting, patients: We prospectively investigated in a private academically-affiliated infertility center 94 consecutive IVF cycles based on 6 criteria for oocyte quality: morphology, cytoplasm, perivitelline space (PVS), zona pellucida (ZP), polar body (PB) and oocyte size, each assigned a value of -1 (worst), 0 (average) or +1 (best), so establishing an average total oocyte score (TOS). Embryo assessment utilized grade and cell numbers of each embryo on day-3 after oocyte retrieval. Clinical pregnancy was defined by presence of at least one intrauterine gestational sac.

Interventions: Standard IVF cycles in infertile women.

Main outcome measures: Predictability of pregnancy based on oocyte and embryo-grading systems.

Results: Average age for all patients was 36.5 ± 7.3 years; mean oocyte yield was 7.97± 5.76; Patient specific total oocyte score (PTOS) was -1.05 ± 2.24. PTOS, adjusted for patient age, was directly related to odds of increased embryo cell numbers (OR 1.12, P = 0.025), embryo grade (OR 1.19, P < 0.001) and clinical pregnancy [OR 1.58 (95%CI 1.23 to 2.02), P < 0.001]. Restricting the analysis to day three embryos of high quality (8-cell/ good grades), TOS was still predictive of clinical pregnancy (OR 2.08 (95%CI 1.26 to 3.44, P = 0.004). Among the 69 patients with embryos of Grade 4 or better available for transfer 23 achieved Clinical Pregnancy. When the analysis was restricted to the 69 transfers with good quality embryos (≥ Grade 4) the Oocyte Scoring System (TOS) (AUC±SE 0.863±0.044, oocyte score) provided significantly greater predictive value for clinical pregnancy compared to the embryo grade alone (AUC 0.646 ± 0.072, embryo grade) p = 0.015.

Conclusions: Oocyte-scoring, thus, provides useful clinical information especially in good prognosis patients with large numbers of high quality embryos. This finding appears of particular importance at a time when many IVF centers are committing sizable investments to closed incubation systems with time-lapse photography, which are exclusively meant to define embryo morphology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Embryo, Mammalian / embryology*
  • Female
  • Fertilization in Vitro / standards*
  • Humans
  • Oocytes / physiology*
  • Pregnancy
  • Treatment Outcome

Grants and funding

This work was supported by the Foundation for Reproductive Medicine and intramural grants from the Center for Human Reproduction (CHR) – New York. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.