Abstract
Research questionWhat are the obstetric and neonatal risks for women conceiving via frozen–thawed embryo transfer (FET) during a modified natural cycle compared with an artificial cycle method. DesignA follow-up study to the ANTARCTICA randomized controlled trial (RCT) (NTR 1586) conducted in the Netherlands, which showed that modified natural cycle FET (NC-FET) was non-inferior to artificial cycle FET (AC-FET) in terms of live birth rates. The current study collected data on obstetric and neonatal outcomes of 98 women who had a singleton live birth. The main outcome was birthweight; additional outcomes included hypertensive disorder of pregnancy, premature birth, gestational diabetes, obstetric haemorrhage and neonatal outcomes including Apgar scores and admission to the neonatal ward or the neonatal intensive care unit and congenital anomalies. ResultsData from 82 out of 98 women were analysed according to the per protocol principle. There was no significant difference in the birthweights of children born between groups (mean difference –124 g [–363 g to 114 g]; P = 0.30). Women who conceived by modified NC-FET have a decreased risk of hypertensive disorders of pregnancy compared with AC-FET (relative risk 0.27; 95% CI 0.08–0.94; P = 0.031). Other outcomes, such as rates of premature birth, gestational diabetes or obstetric haemorrhage and neonatal outcomes, were not significantly different. ConclusionsThe interpretation is that modified NC-FET is the preferred treatment in women with ovulatory cycles undergoing FET when the increased risk of obstetrical complications and potential neonatal complications in AC-FET are considered.
Highlights
I t has been more than 30 years since the first successful frozen embryo transfer (FET) (Trounson and Mohr, 1983; Zeilmaker et al, 1984), and it is increasingly used throughout the world (De Geyter et al, 2018; ESHRE, 2018; Pereira et al, 2019)
Women who conceived by modified natural cycle FET (NC-FET) have a decreased risk of hypertensive disorders of pregnancy compared with artificial cycle FET (AC-FET)
The interpretation is that modified NC-FET is the preferred treatment in women with ovulatory cycles undergoing FET when the increased risk of obstetrical complications and potential neonatal complications in AC-FET are considered
Summary
I t has been more than 30 years since the first successful frozen embryo transfer (FET) (Trounson and Mohr, 1983; Zeilmaker et al, 1984), and it is increasingly used throughout the world (De Geyter et al, 2018; ESHRE, 2018; Pereira et al, 2019). The two most commonly used methods to prepare the endometrium and optimize timing of FET are the artificial cycle (AC-FET) using exogenous oestrogen administration to develop the endometrium and subsequent administration of exogenous progesterone to prepare the endometrium and time FET; or the natural cycle (NC-FET), with a natural build-up of the endometrium while using detection of the LH surge to time the embryo transfer. In 2017 a Cochrane review, focused on endometrium preparation for FET, concluded that no one type of endometrium preparation in FET was to be preferred over another in subfertile women with regular ovulatory cycles (Ghobara et al, 2017). Aside from the chances of pregnancy, the safety of mothers and babies after assisted reproduction should be taken into account
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