Abstract
BackgroundPrevious studies have focused on pregnancy outcomes after frozen embryo transfer (FET) performed using different endometrial preparation protocols. Few studies have evaluated the effect of endometrial preparation on pregnancy-related complications. This study was designed to explore the association between different endometrial preparation protocols and adverse obstetric and perinatal complications after FET.MethodsWe retrospectively included all FET cycles (n = 12,950) in our hospital between 2010 and 2017, and categorized them into three groups, natural cycles (NC), hormone replacement therapy (HRT) and ovarian stimulation (OS) protocols. Pregnancy-related complications and subsequent neonatal outcomes were compared among groups.ResultsAmong all 12,950 FET cycles, the live birth rate was slightly lower for HRT cycles than for NC (HRT vs. NC: 28.15% vs. 31.16%, p < 0.001). The pregnancy loss rate was significantly higher in OS or HRT cycles than in NC (HRT vs. NC: 17.14% vs. 10.89%, p < 0.001; OS vs. NC: 16.44% vs. 10.89%, p = 0.001). Among 3864 women with live birth, preparing the endometrium using OS or HRT protocols increased the risk of preeclampsia, and intrahepatic cholestasis of pregnancy (ICP) in both singleton and multiple deliveries. Additionally, OS and HRT protocols increased the risk of low birth weight (LBW) and small for gestational age (SGA) in both singletons and multiples after FET.ConclusionCompared with HRT or OS protocols, preparing the endometrium with NC was associated with the decreased risk of pregnancy-related complications, as well as the decreased risk of LBW and SGA after FET.
Highlights
Previous studies have focused on pregnancy outcomes after frozen embryo transfer (FET) performed using different endometrial preparation protocols
Endometrial preparation protocols can be commonly divided into three methods: natural cycles (NC) using spontaneous ovulation, ovarian stimulation (OS) protocols performed with endogenous steroids, and hormone replacement therapy (HRT) protocols involving artificial preparation with exogenous steroids [4, 5]
The rate of live birth was lower in patients who underwent HRT cycles than in those who underwent an NC cycle (HRT vs. NC: 28.15% vs. 31.16%, p < 0.001), while a comparable live birth rate was observed between patients who underwent endometrium preparation with the NC or OS protocol (NC vs. OS: 31.16% vs. 31.01%, p = 0.920)
Summary
Previous studies have focused on pregnancy outcomes after frozen embryo transfer (FET) performed using different endometrial preparation protocols. Few studies have evaluated the effect of endometrial preparation on pregnancy-related complications. This study was designed to explore the association between different endometrial preparation protocols and adverse obstetric and perinatal complications after FET. Many cohorts have been studied and randomized controlled trials performed to evaluate the effects of these endometrial preparation protocols on pregnancy outcomes for FET; their findings remain controversial [5,6,7,8]. Compared to the pregnancy outcomes achieved after FET, few studies have explored the effect of endometrial preparation on pregnancy-related complications and subsequent neonatal outcomes
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