Your menstrual cycle is governed by hormones. These hormones help the lining of the uterus grow and thicken ready to receive an embryo should you become pregnant.
The key hormones to be aware of in this equation are oestrogen and progesterone. Oestrogen thickens the lining of the uterus (the endometrium), while progesterone balances it out, keeping the endometrium thin. The endometrium is the tissue that comes out as menstrual blood during your period. If the oestrogen is not well balanced by the progesterone, you’re likely to have a thicker endometrium. A thicker endometrium means there’s more tissue to shed, hence the heavy flow. A thicker endometrium also contains more blood vessels, which contributes to a heavier period.
It follows that any hormonal changes you experience can affect the endometrium and therefore how much you bleed during your period.
Changing hormonal contraceptive
Switching from one hormonal contraceptive to another can disrupt your hormonal balance in a similar way. This is usually temporary and only lasts a few months. In general, hormonal contraceptives reduce the amount you bleed once you’ve been on them for a few months. All hormonal contraceptives contain types of progesterone (remember, this is the hormone that keeps the lining thin). It's also common to experience a heavier or earlier period if you take an emergency hormonal contraceptive (eg morning after pill).
A common side effect of the copper coil contraceptive is heavier periods. Several theories try to explain this including inflammatory changes, physical irritation and vascular changes to the endometrium. If you find that there is a significant change, for example, if you experience flooding, clotting or pain, ask your healthcare provider about changing to a progestogen-containing coil or taking non-hormonal medication to alleviate the symptoms.
In the years approaching menopause (when your periods stop) there can be fluctuations in your hormones. As a result, your periods can fluctuate as well.
Pregnancy loss or postpartum
After experiencing a pregnancy, your hormonal cycle has to reset, leading to possible changes in your period. The same applies to pregnancy loss.
People who have been exercise-training, or have lost significant weight, may find that their periods reduce in flow, become sporadic or even stop altogether. In simple terms, your body recognises you’re under stress and tries to conserve energy. It also deems it to be an ‘unsafe’ time for pregnancy and so interrupts your normal hormonal cycle to prevent ovulation.
As you reduce this training or start to gain weight, your periods can return to a more regular cycle and can be heavier than before. Women who develop excessive adipose tissue (body fat) produce oestrogen from this tissue and, as we know, oestrogen thickens the endometrium resulting in heavier blood flow.
Being under physical and emotional strain can disrupt your body’s systems, including your hormonal cycles. Some people experience irregular or lighter periods when they are stressed, while others find that their periods come less often, but are heavier as a result.