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Are You Fertile Before Your Period?

Finding out when you are most fertile is important if you’re trying to get pregnant, but it’s not easy. If you’re not consciously targeting your fertile window – the time in each cycle when the lifespan of the egg you ovulate overlaps with the average lifespan of sperm, and your fertility is at its natural peak – then you’re denying yourself one of the biggest advantages available to you!

Determining when your fertile window will fall means monitoring your menstrual cycle: you are at your most fertile in five days running up to when you ovulate, so you need to identify the signs that tell you when you’re ovulating. This isn’t as easy as it sounds: your period is the most visible, obvious sign of where in your cycle you are, but you’ll get more information to find out when you’re fertile.

The key event is ovulation: if you can find out when you ovulate, you can count back to find out when your fertility window begins. The most reliable way to do this is to log your basal body temperature. This is the lowest temperature your core drops to during long periods of rest as your metabolism slows down. It varies by small amounts (as little as a tenth of one degree) in response to changes in your body, and if you know the right pattern to look for, you can use it to detect when you’re due to ovulate.

OvuSense can help here, as our system uses an automated sensor to take your temperature at intervals right through the night, so you know you have accurate results, and processes those results into a prediction that’s tailored to your body, however regular or irregular your cycle.

Technically your fertile window happens after your period: your period is the beginning of your menstrual cycle, and at the same time as it begins your body begins to prepare eggs to be ovulated. Ovulation occurs, on average, 16 days after your period starts, but it can vary – anywhere between 11 and 23 days is within the normal range for an adult woman. Following ovulation your body begins focuses on building a thick lining in the uterus to sustain the egg and help it develop if it is fertilised and does implant.

This phase of your menstrual cycle is known as your luteal phase and normally lasts between 11 and 14 days. This means that you wouldn’t normally be fertile immediately before your period.

Find out more about core temperature technology and fertility here