1. The type of culture media and the duration of embryo culture were not associated with changes in birthweight in singletons born using assisted reproductive technologies (ART).
2. These findings contradict previous studies.
Evidence Rating Level: 2 (Good)
Study Rundown: The use of assisted reproduction technologies (ART), such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), has grown in recent years, raising concerns about the impact such techniques have on birth outcomes. Infants born following ART are more likely to be preterm, small for gestational age, or low birthweight compared with spontaneously conceived infants, but it is still unclear at what point in the process this increased risk is conferred. Some previous studies have suggested that the type of solution (medium) used to grow embryos and the duration of time grown outside the body prior to implantation may impact birthweight. However, many of the studies were small and of poor quality, so findings are still inconclusive. In this study, researchers used a large retrospective database to obtain stronger evidence to determine whether culture media type and duration of culture impacted birthweight in singletons born after ART.
Neither type of culture media nor duration of culture (3 days vs. 5 days) was associated with changes in birthweight. This is in contrast to previous findings. Strengths of this study included the large sample size and ability to control for many potentially confounding variables. Pregnancy-associated factors known to be associated with low birthweight, such as pre-eclampsia, were not included in multivariate models. Additionally, only fresh embryo transfers were studied. Therefore, results may not be extended to other forms of ART that use frozen embryos. As this is a hotly debated topic and will likely become more important as rates of ART births increase, future randomized, prospective studies examining the impact of culture duration and type are merited.
Relevant Reading: Further evidence that culture media affect perinatal outcomes
In-Depth [retrospective cohort study]: All singleton live births after fresh embryo transfer performed at a single tertiary care center from 2004-2009 were included in the analysis (n=2098). Two types of culture media were used, Medicult (n=1388) and Vitrolife (=719) and transfers occurred on either Day 3 (n=1234) or Day 5 (n=864) of culture. The primary outcome was birthweight. Other variables taken into account included maternal age, maternal/paternal BMI, parity, maternal smoking status, method of fertilization (IVF+/- ICSI), cause of infertility, number of embryos transferred, stimulation protocol, gestational age, and newborn gender.
Newborn birthweight did not differ by culture type (Medicult versus Vitrolife, p=0.264). Similarly, there was no difference in birthweight between embryos transferred on Day 3 or blastocysts transferred on Day 5 (p=0.209). Birthweight was affected by maternal parity, maternal smoking status, gestational age and newborn gender but not culture duration or stimulation protocol.
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