The menstrual cycle

Menstruation – your period – is the part of your menstrual cycle when you’re bleeding. This is the phase when you’re least likely to get pregnant – but it’s still possible. Having your period is not a form of contraception.

What’s happening in your body when you have your period:

• Your uterus lining sheds and flows out of your vagina. This flow also includes cervical mucus and vaginal discharge.
• Your oestrogen levels are at their lowest.
• You might have low energy.
• You might have cramps, headaches, and bloating.
• Your chance of getting pregnant is the lowest.

The follicular phase starts from your period and goes on for around another nine days. During this phase, your oestrogen increases, and so does your energy. The more this phase progresses, the more likely you are to get pregnant. 

What’s happening in your body:

• Your uterus lining thickens.
• The follicles in your ovaries grow.
• Your oestrogen increases.
• Your chance of getting pregnant increases.
• You start to feel more energetic.
• You start to have more cervical mucus or vaginal discharge.

Ovulation is when the egg is released from the ovary and travels to the uterus. You’re most likely to get pregnant three days before ovulation and then during ovulation. This is when your energy levels are at their highest.

What’s happening in your body:  

• An egg is released from the ovary and travels to the uterus.
• Your oestrogen peaks just before ovulation, then starts to decrease.
• Your chance of getting pregnant is the highest.
• You have a lot of energy.
• Your vaginal discharge is thicker, with a texture like egg white.

In the early luteal phase, the lining of your uterus thickens to prepare for a possible fertilised egg. Your level of the hormone progesterone increases, and this can cause premenstrual syndrome (PMS) symptoms like tender breasts, bloating, and mood swings.

What’s happening in your body: 

• Your uterine lining stabilises and matures.
• Your progesterone level increases, and oestrogen level decreases.
• Your cervical mucus thickens, creating a cervical plug.
• Some people have PMS symptoms, including headaches, pimples, sore breasts, bloating, and mood swings.
• Your chance of getting pregnant is decreasing, but it’s still possible. 

In the late luteal phase of your menstrual cycle, your body is preparing for your next period. Your levels of progesterone and oestrogen start to decrease. Your chance of pregnancy is low, but it could still happen if you have unprotected sex.

What’s happening in your body:

• Your levels of oestrogen and progesterone decrease.
• Your vaginal discharge decreases, but your cervical mucus plug remains thick.
• You may have premenstrual symptoms, such as tender breasts, bloating, mood swings, headaches, and cramps.
• Your chance of getting pregnant is low.

Your menstrual cycle is your body’s way of preparing to get pregnant. Your menstrual cycle is made up of different phases, and which phase you’re in will affect your fertility – how likely you are to get pregnant.

Your chance of getting pregnant is lowest when you’re on your period, and highest just before and during ovulation. But it’s possible to get pregnant at any time in your menstrual cycle, so if you don’t want to, it’s a good idea to use contraception. 

Hormonal contraception can give you control over your ability to get pregnant.

Most types of hormonal contraception – like the contraceptive pill, implant, and depo provera injection – keep your hormones at a stable level. This means your body won’t go through the menstrual phases in the same way. With some types of hormonal contraception, you’ll still have your period, but with other types, you can choose not to – like if you take the combined oral contraceptive pill continuously. 

If you become pregnant, you won’t get your period. Some small spots of blood on your underwear can be normal during a pregnancy, but if you’re worried, make an appointment with a medical professional. Find out more about how your body will change when you’re pregnant on Health NZ.

If you choose to continue the pregnancy, your menstrual cycle will also change after pēpi arrives. Your period might not come back for a while after giving birth, especially if you’re breastfeeding.  

But even if your period hasn’t come back again, it’s still possible to get pregnant, so we recommend starting contraception straight away. Some types of contraception, like progestogen-only contraception don’t affect breastfeeding or your pēpi’s growth.

Once your period does come back, it might be different to before you were pregnant. If you’re worried or your period is a problem for you, make an appointment to talk to us, or talk to your GP.