Timing of oocyte retrieval and embryo transfer with pregnancy duration

Recent studies have suggested that assisted reproductive technology (ART) may be associated with a shorter pregnancy duration, possibly due to various aspects of the ART procedure. The purpose of this study was to examine whether pregnancy duration is affected by timing of oocyte retrieval and embryo transfer with respect to the first day of the last menstrual period (LMP) among pregnancies achieved through in vitro fertilization with or without intracytoplasmic sperm injection.

A retrospective study was conducted at an academic center in Norfolk, Virginia, with analyses based on 294 ART cycles.

Median and interquartile range for pregnancy duration was estimated at 38.2 ± 3.4 weeks. Similarly, median and interquartile ranges for days between LMP and day of oocyte retrieval (27.0 ± 2.0) and between LMP and embryo transfer (29.8 ± 2.2) differed significantly from the standard of 14 days. Timing of oocyte retrieval and embryo transfer with respect to LMP were accelerated among multiple compared with single gestations. For single gestations, pregnancy duration was positively associated with time duration between LMP and embryo transfer (β=0.14, p=0.036). The number of days between oocyte retrieval and embryo transfer was marginally associated with a shorter pregnancy duration in women with multiple gestations (β=3.70, p=0.083). Controlling for patient characteristics, timing of oocyte retrieval and embryo transfer were not significantly associated with pregnancy duration.

With few exceptions, timing of oocyte retrieval or embryo transfer did not affect pregnancy duration among ART-conceived live births.