Fresh or frozen? That is the question.
Unfortunately, there is no one-size-fits-all answer when it comes to IVF, or in-vitro fertilization. According to a recent study of almost 83,000 IVF patients, it completely depends on the patient as to whether or not transferring a fresh or frozen embryo will offer the best opportunity for a healthy baby.
There are several factors that doctors consider before making a decision, including how many eggs a woman produces. And while some women benefit from a fresh embryo transfer, others benefit from a frozen transfer that is slightly delayed.
So what does 'delayed' mean, exactly?
First, it helps to explain the process involving a fresh transfer. During a fresh transfer, a woman prepares by taking hormone injections for several weeks prior, which helps to stimulate egg production. Doctors then retrieve the eggs, fertilize them, and then place one or more embryos in the mother. In a delayed transfer, after fertilization the embryos are frozen, and doctors wait several weeks for the patient to enter a new menstrual cycle before transferring the embryo(s).
Advocates of delayed frozen transfers claim that what a woman's body goes through to prepare for IVF makes it a little more hostile to pregnancy - which is why waiting until the next cycle is a good approach.
"In the past five years, some clinics have advocated for freezing everything with the belief that the process that stimulated the eggs makes the lining of the uterus less welcoming for pregnancy," said Dr. Suheil Muasher, a reproductive endocrinology and infertility specialist and senior author of the study, which was published in the journal Fertility and Sterility on August 20. Dr. Muasher added that some research has also shown that frozen embryo transfers are less likely to result in problems down the road such as preterm labor and underweight babies.
The study claims however, that delayed frozen transfers may only be better for women who produce 15 or more eggs, dubbed "high responders". This is because data shows that for women who produced 14 eggs or fewer ("low and intermediate responders"), fresh transfers led to better pregnancy and birth rates.
For women over 40, there's even more to consider - particularly when it comes to freezing your eggs. According to The Human Fertilisation and Embryology Authority (HFEA), egg freezing into your 40s is not recommended as fertility declines with age. Despite this, many women in the UK are still freezing eggs into their 40s, with data showing the most common age of treatment at 38.
"Clinics have an ethical responsibility to be clear that egg freezing below the age of 35 offers women their best chance of creating their much longed-for family," said Sally Chesire, HFEA Chair.