Fertility treatment: Storing vitrified embryos longer reduces chances of pregnancy

Longer storage of embryos using a technique called vitrification also decreases the chances of having a live birth, a new study suggests.

By: Longjam Dineshwori | Edited by: Longjam Dineshwori | | Updated: June 25, 2020 10:11 pm

Tags: Egg freezing Infertility treatment

The rate of miscarriages and ectopic pregnancies increases with longer embryo storage time.

Are you going for any fertility treatment? If it is in vitro fertilization (IVF), the process requires freezing and storing one or more embryos (fertilized eggs) for future use. Vitrification is a technique of freezing the fertilized egg/eggs during fertility treatment, but there have been concerns that this process could be unsafe for the embryo, and lead to complications at the time of birth and later. Clearing all the doubts about this egg freezing technique, a new study has revealed that vitrification is safe for embryos – but longer storage may reduce chances of pregnancy success. Also, the longer the embryos are stored, the lesser women are likely to have a live birth – it said. Also Read - Not able to conceive? Blocked fallopian tubes may be to blame

The study suggested that although longer storage of vitrified embryos was associated with decreased pregnancy and live birth rates, it did not affect neonatal health. This is reassuring news for couples seeking fertility treatment, noted the researchers. The research was published in Human Reproduction. Also Read - Female infertility: 6 herbs that can help you get pregnant

Consider storage duration before freezing embryos

In vitrification process, the eggs are frozen so rapidly that the water molecules don’t get time to form ice crystals, and instead instantaneously solidify into a glass-like structure. When the eggs are needed, the freezing process is reversed to thaw and warm the embryos quickly. Also Read - Are you going through fertility treatment? Don't let your sex life take a beating

For the study, the researchers looked at the outcomes of 24,698 patients who had vitrified embryos transferred for the first time between January 2011 and December 2017. They were divided into four groups based on the duration of storage of their embryos. Group 1 – those who had embryos stored for up to three months; Group 2 – whose embryos were stored for three to six months; Group 3 – embryos stored for six to 12 months and Group 4 – embryos stored for 12-24 months. Here are some key findings of the study:

Implantation rate fell from 40% in group one to 26% in group four.
Clinical pregnancy rate fell from 56% in group one to 26% in group four
Live birth rate fell from 47% in group one to 26% in group four.
No association found between embryo storage time and neonatal outcomes.

Based on these findings, the researchers said that 47 out every 100 women, who had embryos stored for less than three months, would have a live birth. And 34 out of every 100 women, who had embryos stored for between 12-24 months, would have a live birth.

The rate of miscarriages and ectopic pregnancies also increased with longer storage time, the researchers noted.

Therefore, the researchers suggested that clinicians should consider the effect of storage duration before making decisions about the numbers of embryos to freeze and store.

Other factors that can determine your pregnancy

It’s not just the embryo storage duration that might affect your fertility treatment outcomes. Your changes of getting pregnant may also depend on many other factors such as the mother’s age, mother’s body mass index, the cause of infertility, parity and embryo quality and stage of development.

Moreover, the new study has some limitations, including that it did not to show the effect of storing embryos for longer than 24 months. Also, the researchers did not undertake long-term follow-up of babies, and so there’s no information about their growth and development.

Published : June 25, 2020 10:03 pm | Updated:June 25, 2020 10:11 pm

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