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Meta-Analysis
. 2020 Jul;302(1):31-45.
doi: 10.1007/s00404-020-05593-4. Epub 2020 May 22.

Neonatal outcomes in singleton pregnancies conceived by fresh or frozen embryo transfer compared to spontaneous conceptions: a systematic review and meta-analysis

Flavia T S Elias  1   2 , Danielle Weber-Adrian  1 , Jessica Pudwell  1 , Jillian Carter  1 , Mark Walker  3 , Laura Gaudet  1 , Graeme Smith  1 , Maria P Velez  4   5
Affiliations
Meta-Analysis

Neonatal outcomes in singleton pregnancies conceived by fresh or frozen embryo transfer compared to spontaneous conceptions: a systematic review and meta-analysis

Flavia T S Elias et al. Arch Gynecol Obstet. 2020 Jul.

Abstract

Purpose: The use of assisted reproductive technology (ART) has increased in the last 2 decades and continuous surveillance is needed. This systematic review aims to assess the risk of adverse neonatal outcomes (preterm birth [PTB], low birth weight [LBW], small-for-gestationalage [SGA] and large for gestational-age [LGA]), in singleton pregnancies conceived by fresh or frozen embryo transfer (FET) compared to spontaneous conceptions.

Methods: Cohort studies were identified from MEDLINE, Embase, Cochrane Library (January 2019), and manual search. Meta-analyses were performed to estimate odds ratios (OR) using random effects models in RevMan 5.3 and I-squared (I2) test > 50% was considered as high heterogeneity.

Results: After 3142 titles and abstracts were screened, 1180 full-text articles were assessed, and 14 were eligible. For fresh embryo transfer, the pooled ORs were PTB 1.64 (95% CI 1.46, 1.84); I2 = 97%; LBW 1.67 (95% CI 1.52, 1.85); I2 = 94%; SGA 1.46 [95% CI 1.11, 1.92]; I2 = 99%, LGA 0.88 (95% CI 0.80, 0.87); I2 = 80%). For frozen, the pooled ORs were PTB 1.39 (95% CI 1.34, 1.44); I2 = 0%; LBW 1.38 (95% CI 0.91, 2.09); I2 = 98%; SGA 0.83 (95% CI 0.57, 1.19); I2 = 0%, LGA 1.57 (95% CI 1.48, 1.68); I2 = 22%).

Conclusions: When compared with spontaneous pregnancies, fresh, but not frozen was associated with LBW and SGA. Both fresh and frozen were associated with PTB. Frozen was uniquely associated with LGA. Despite improvements in ART protocols in relation to pregnancy rates, attention is needed towards monitoring adverse neonatal outcomes in these pregnancies.

Keywords: Adverse neonatal outcomes; Assisted reproductive technology; Fresh embryo transfer; Frozen embryo transfer; Meta-analysis; Real-world data.

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Conflict of interest statement

The authors declare no competing interests that might have influenced the work described in this manuscript.

Figures

Fig. 1
Fig. 1
Flowchart identification and selection of included studies
Fig. 2
Fig. 2
Forest plot of singleton pregnancies resulting from fresh embryo transfer compared to spontaneous conceptions, in relation to a preterm birth and b low birth weight
Fig. 3
Fig. 3
Forest plot of singleton pregnancies resulting from fresh embryo transfer compared to spontaneous conceptions, in relation to a small for gestational age and b large for gestational age
Fig. 4
Fig. 4
Forest plot of singleton pregnancies resulting from IVF/ICSI in frozen embryo transfer cycles compared to spontaneous conceptions, in relation to a preterm birth and b low birth weight
Fig. 5
Fig. 5
Forest plot of singleton pregnancies resulting from IVF/ICSI in frozen embryo transfer cycles compared to spontaneous conceptions, in relation to a small for gestational age and b large for gestational age
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