Abstract
BackgroundSmooth endoplasmic reticulum aggregation (SERa, SER+) has been reported to increase the risk of birth malformations and other abnormal outcomes, miscarriage, and perinatal complications. Other studies, however, suggest that SER+ embryos may develop into healthy infants. One report indicates that 25% of in vitro fertilization (IVF) centers discard SER+ oocytes. Thus, we investigated the effect of SER+ on birth outcomes in IVF and intracytoplasmic sperm injection.MethodsWe performed a literature search using PubMed, ScienceDirect, Cochrane, Embase, Ovid, and Scopus. We found a total of 1500 relevant studies between 1978 and 2020 and conducted a meta-analysis to study the effects of SER+ on live births, birth weight, and the number of metaphase II (MII) oocytes retrieved per cycle.ResultsEleven eligible studies were included. If the SER+ zygote was evaluated again at the embryo transfer (ET) stage, SER+ did not affect birth or infant body weight. Stimulated ovaries producing too many oocytes per cycle were positively correlated with SER+ (OR = 1.28, 95% CI = 0.41–2.15; p = 0.004). SER+ was positively correlated with oocyte maturation rate, and observed heterogeneity in a previous meta-analysis was likely due to maternal age. Our data also showed that SER+ cycles produced more oocytes but achieved the same number of births from ET.ConclusionsThe use of SER+ MII oocytes is rare, with the collection of many oocytes in 1 cycle potentially inducing SER+. SER+ may be more common than we originally thought, as some SER+ is found in all oocytes. Although SER+ positively affected oocyte maturation rate, it did not affect births. We hypothesized that this is because the best embryos are chosen at every step of the process, and the oocytes with the poorest characteristics are removed. We therefore suggest a standard method for measuring SER+. Although embryos produced from SER+ cycles can be used, they should only be transferred when no other suitable embryos are available over several cycles.
Highlights
Smooth endoplasmic reticulum aggregation (SERa, smooth endoplasmic reticulum (SER)+) has been reported to increase the risk of birth malformations and other abnormal outcomes, miscarriage, and perinatal complications
We included in our meta-analysis eligible studies that were published less than years ago (Table 2) [3, 4, 10, 12,13,14,15, 21,22,23,24], and we noted that ovarian stimulation protocols were very common among them
We analyzed births and SER+ cycles (Fig. 2a) and SER metaphase II (MII) oocytes (Fig. 2b), and observed no differences between SER+ (OR = 1.13, 95% CI = 0.99–1.3; p = 0.35)
Summary
Smooth endoplasmic reticulum aggregation (SERa, SER+) has been reported to increase the risk of birth malformations and other abnormal outcomes, miscarriage, and perinatal complications. One report indicates that 25% of in vitro fertilization (IVF) centers discard SER+ oocytes. Clinical studies have indicated that smooth endoplasmic reticulum aggregation (SERa or SER+) may increase the risk of birth malformation or other abnormal outcomes [1,2,3,4,5], miscarriage [2], and perinatal complications [3]. During in vitro fertilization (IVF), SER+ appears in 10% of ovulationinduction cycles and in 19–34% of oocytes [6]. Embryologic research has revealed that the smooth endoplasmic reticulum (SER) regulates early embryonic development via energy accumulation [4] and plays a key role in calcium storage and release [9]. Researchers have even reported the occurrence of complex chromosomal rearrangements with consistent 2q31 deletions [5]
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