The Patient's Guide to Embryology

The basic steps to create and grow embryos are always the same:

  1. Combine eggs and sperm to get fertilization
  2. Grow embryos in carefully controlled conditions for up to 7 days
  3. Select the embryos suitable to use and discard the remaining ones

There are differences in the technology used to complete these steps and there are additional treatments that can be used along the way too, all with the aim of creating as many healthy embryos as possible.

Remember that not all embryos are successful and many factors can affect their potential to make a baby.

How are embryos made?

Before embryos can be created, eggs need to be collected from a woman’s ovaries. Eggs at the right stage of maturity are fertilised outside the body either by placing them in close contact with sperm ( traditional IVF) or by injecting sperm directly into the egg (ICSI). Fertilization takes around 20 hours and then the first stages of embryo development begin.

To grow an embryo outside the body, it needs to be kept in carefully monitored conditions. In a natural pregnancy it takes the embryo 5-6 days to travel down the fallopian tube before entering the uterus where it will implant into the womb lining. Everything in the IVF lab aims to mimic the body’s natural environment and timings as closely as possible – this is why the best day for an embryo transfer is 5 days after fertilization.

Take a closer look

Frozen embryo transfers

The success rates of frozen embryo transfers have increased dramatically and the chance of getting pregnant is now equal to a fresh embryo transfer, if not better… Read more.

Preimplantation genetic testing (PGT-A)

Preimplantation genetic testing for aneuploidy (PGT-A) is an optional add-on treatment which is becoming increasing popular in IVF… Read more.

Embryo development from days 1-6

Coming soon…

Does double embryo transfer double your chance?

A double embryo transfer is when you create embryos in the lab through IVF and place two of them into the uterus instead of one… Read more.

PGT-A – are my embryos at risk?

Embryos are surprisingly resilient but there are still some risks associated with PGT-A… Read more.

PGT-A results explained

A checks all 23 pairs of chromosomes to determine whether embryos are abnormal (aneuploid)… Read more.

Timelapse incubation – is it worth the money?

Timelapse incubators allow embryologists to monitor embryos without disturbing them as they develop… Read more.

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