Assisted conception

IVF: the danger of ectopic pregnancy

In vitro fertilisation (IVF) has come a long way since the first successful procedure in 1987 resulted in the birth of the first IVF baby, Louise Brown. Now – 37 years later – there are over 5 million IVF babies and the procedure has been getting more advanced and more efficient all the while.

But that’s not to say IVF doesn’t have it faults. Reproduction is a very complicated biological process. So getting all the ins and outs and specific timings and procedures in perfect balance – so as to mirror a natural and seamless pregnancy – isn’t an easy feat.

Ectopic pregnancy

One of the problems that arises more often in IVF procedures than in natural conceptions is ectopic pregnancy. Usually, during implantation, a fertilised embryo embeds into the walls of the uterus. But during an ectopic pregnancy, an embryo implants somewhere outside of the uterus, usually in the fallopian tubes (which connect the ovaries to the uterus). And here the embryo cannot develop into a healthy pregnancy, since it has no room to grow.

Sometimes the embryo dies before it can grow. Other times ectopic pregnancy is treated with medication. However, if the problem is not picked up on until later, the woman may need surgery to remove the embryo, or in the worst case scenario, the growing embryo can cause a life-threatening rupture of the fallopian tube in which it is growing.

Researchers believe ectopic pregnancies are more likely to occur in IVF pregnancies than in those which are natural because there is a different hormonal and chemical environment in the uterus during IVF compared to during natural pregnancy. The balance of hormones and chemicals during IVF is manipulated by doctors and the mixture may be more likely to induce an ectopic pregnancy.

But that isn’t the only layer to the story.

Fresh and frozen eggs

Eggs used for IVF can either be fresh or frozen. When a women undergoes an IVF treatment, her ovaries are stimulated to release eggs. These are collected (or ‘harvested’) and then used immediately to create an embryo with sperm or frozen for preservation so they can be thawed and used for later IVF cycles. Eggs collected from donors for use in IVF are also usually frozen.

Strangely, new research published in the Fertility and Sterility journal has shown that whether or not a frozen egg is used during an IVF procedure can affect the likelihood of a woman having an ectopic pregnancy.

During IVF cycles with frozen eggs and donor eggs, the resulting fertilised embryo is transferred to perfectly coincide with a woman’s natural ovulation cycle. Alternatively, it might be transferred with hormone supplements that suppress the release of eggs from the ovaries. Fresh eggs, on the other hand, are transferred to the woman’s uterus with a higher concentration of hormones than the concentration that naturally occurs.

Because the hormone environment of the uterus more closely resembles natural conditions during conception in frozen egg IVF cycles, the researchers predicted that there was more chance of ectopic pregnancy during IVF cycles with fresh eggs. So they studied 103,070 IVF cycles carried out in the USA – 1.38% of which resulted in ectopic pregnancies.

In IVF cycles where women used their own eggs, the researchers found that the chances of ectopic pregnancy were 65% lower in women who had used frozen eggs compared to those who had used fresh eggs.

IVF cycles using donor eggs were less likely to result in ectopic pregnancies compared to cycles where women used their own eggs. However, there was no difference in ectopic pregnancy likelihood whether the donor egg was frozen or fresh.

The researchers also found that the chances of ectopic pregnancy increased when three or more embryos were transferred during IVF.

It just goes to show, the hormonal environment in the fallopian tubes and in the uterus during IVF – and during natural conception – can have a huge impact on how a pregnancy can turn out. Pregnancy is a very complicated process and we still have a lot to learn about how it works. But the more we know about pregnancy, the more success procedures like IVF will have.

Who knows where IVF will take us in the next 37 years?

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