Embryo freezing, also called embryo cryopreservation, is a way of preserving fertilised embryos by cooling them to a very low temperature and storing them safely, so you and your partner can use them later in a frozen embryo transfer, or FET.

Most embryos are frozen as part of an IVF cycle, when a couple has more good embryos than they will use in one go. Others are frozen deliberately, for example before medical treatment that could affect fertility, or when the time for a baby is not now but may come later.

The freezing itself uses vitrification, a fast-freezing method that is the standard used worldwide. Embryos are usually frozen at day five, once they have grown into what is called a blastocyst, though some are frozen earlier at day three.

Because an embryo is created from both partners, freezing embryos needs both partners' consent under India's ART Act 2021. We explain exactly what that means in plain terms further down the page.

• Take your medication exactly as prescribed The timing of the injections matters. Set reminders, and do not skip or delay a dose without checking with your specialist first.
• Ease off strenuous activity late in the cycle As the ovaries respond, they enlarge a little. Hard exercise in the last few days carries a small risk, so keep it gentle. Walking is fine.
• Watch for signs of OHSS Some bloating is normal. Severe pain, rapid weight gain, persistent nausea, or breathlessness are not normal and mean you should call us straight away.
• Go easy on alcohol, tobacco, and caffeine Avoid alcohol and tobacco through the cycle, and keep caffeine to about one cup a day.
• Plan around the retrieval day Egg retrieval is a half-day procedure under sedation. Take the day off, keep the next day quiet, and have someone bring you home.
• Eat well, stay hydrated Balanced, protein-rich meals and plenty of water support you through the cycle and the days after retrieval.