Storing embryos for long periods impedes pregnancy success

For most couples, having children happens naturally and as planned.

Unfortunately, that is not usually the case for some individuals. After trying to have children unsuccessfully, health experts usually advise affected couples to consider using the In-Vitro Fertilisation (IVF) technique.

During the procedure, doctors take eggs from a woman and fertilise them with sperm outside the body.

The fertilised eggs, known as the embryo, can then be transferred to the woman’s uterus or womb, where it will follow the normal infant development stages and enable the mother to deliver after nine months.

In other instances, couples may decide to delay the implantation so they can have children at a later date.

CANCER TREATMENT

For example, women going through cancer treatment are usually advised to wait until they are well before having babies.

With the increasing work demands and pressures, some couples also delay having kids until they are in the right frame of mind.

Embryos may also be preserved so they can be used in multiple IVF procedures in case the previous ones are not successful.

For effective preservation, the embryos are usually frozen through vitrification.

With this technology, embryos are briefly placed in a dehydrating solution, then fast-frozen to prevent damaging ice crystals from forming.

Despite the use of this procedure, there have been concerns that the procedure could be unsafe for the embryo, leading to adverse health effects for the unborn such as being born prematurely or having birth defects.

It has also been unclear whether storage time after freezing (vitrification) affects the viability of the embryos to yield successful pregnancy and improved well-being for the unborn.

A new study published in the Human Reproduction Journal offers clarity.

It shows that the vitrification process is safe, but women are less likely to become pregnant and have a live birth the longer the embryos are stored.

FOUR GROUPS

During the study, researchers from the Shanghai Ninth People’s Hospital based in China analysed outcomes of 24,698 women that used frozen embryos to get babies.

The women were divided into four groups.

The first group used frozen embryos stored for up to three months while the second one had preservation for three to six months.

Mothers in the third group relied on those frozen for six to 12 months while the last used those kept for between one to two years.

Based on the results, pregnancy rates fell from 56 percent in the first group to 26 percent in the last.

In addition, the live birth rate fell from 47 percent to 26 percent in the former and latter group respectively.

The rate of miscarriages and ectopic pregnancies also increased with longer storage.

However, these associations were not statistically significant after taking into account other factors that affect pregnancy, including the mother’s age, mother’s body weight, the cause of infertility, embryo quality and stage of development.

HEAVY BURDEN

There was also no evidence that storage time affected neonatal outcomes or the health of babies.

“We think the results from this analysis support our main results about the relationship between the duration of storage with pregnancy and neonatal outcomes [newborn health],” said Dr Qianqian Zhu, the lead author of the study.

“This is reassuring news for couples seeking fertility treatment. If we had found that neonatal [newborn] health was adversely affected by vitrification, it would impose a heavy burden on individuals, family and society,” stated Prof Qifeng Lyu, a co-author and deputy director of the department of assisted reproduction at Shanghai Ninth People’s Hospital.

Dr Zhu said: “Our results suggest that clinicians should consider the effect of storage duration before making decisions about the numbers of embryos to freeze and store.

“This is especially important for cancer patients, who may have their ovaries destroyed by cancer therapies and who have to delay fertility treatment until they have recovered from their disease.”