I don’t know my uterus as well as I should. Who does? We are not, as girls, much encouraged to peer into our interiors or to learn properly about fallopian tubes and eggs. I don’t mean that this wasn’t taught in biology classes, but that it’s not taught in a way that is meaningful or that sticks. Or, if it is, then the meaningfulness of it is weakened and diluted by the everyday context where women’s periods live: in taboo and embarrassment. Even a BBC guide for young women describes periods as “uncomfortable, and [not] very pleasant generally”.
Show me an advert for sanitary products that does not advertise their fragrance and discretion. Periods are meant to be both hidden and “feminine”, but not in a way that means they are celebrated as a mark of a woman’s fertility, or of how wondrous our female bodies are. If I’d known I was born with a million eggs in my ovaries, like most girls, I’d have boasted of it in my teens. And I’d have been delighted to tell boys that my clitoris has twice as many nerve endings as their penis.
Yet for most of my life, I have been conditioned to think of my period as something to endure, hide or mask, rather than a sort of normal biological procedure. Sort of normal, because science is still trying to understand why human females menstruate at all: apart from us, only bats, shrews and primates menstruate, and rarely. Modern women spend 3,000 days of their life menstruating, on average. For something that takes up that much time, menstruation is still enticingly mysterious.
Here is the biological bit: your period may be late for all sorts of reasons. Periods, like many bodily functions, are governed by the hormone-emitting pituitary gland in the brain. Oestrogen, progesterone, FSH (follicle-stimulating hormone): our endocrine system sends hormones around the body to regulate all sorts of processes, procedures and activities, including the monthly act of preparing for a possible foetus by having your ovaries release an egg. Your uterus prepares by making a thick, comfortable, nutrient-rich extra lining called an endometrium that a foetus – which is after all a kind of parasite – can grow in and feed from. The endometrium is filled with blood vessels to feed a growing human. Think of it as a nutrient mattress-topper. No foetus, no topper needed, and the endometrium will be discarded as your period: up to 90ml of bloody discharge released over, usually, up to seven days.
The most obvious answer to why your period is late is pregnancy: fertilisation of the monthly egg has occurred, and your endometrium is staying put to house the foetus. But there are other reasons that periods disappear or are late. Diseases and conditions such as endometriosis or polycystic ovaries can disrupt menstruation, but also disorders of the thyroid, another important hormonal performer, or any hormonal upheaval. Very underweight and overweight girls and women can have disrupted periods, as can people having radiation or chemotherapy. Some drugs upset the menstrual cycle. Premature menopause sends hormones haywire, just like the regular peri- or menopause.
Stress can stop periods, by decreasing levels of gonadotropin-releasing hormone (GnRH), which controls oestrogen release; and doing some extraordinary activity like running a marathon may cause your body to switch to protective mode, signalling the womb not to build an endometrium, an energy-using process, and to save energy as you might need it.
I had a six-month period of amenorrhoea last year, which was either due to my age (45), my endometriosis, my decision to run the London marathon, or all three.
The pituitary gland is a sensitive and marvellous thing: I still thank it for stopping my periods for three months when I was camping in Siberia, and when using pit latrines dug in forests was bad enough without the hassle of a period. I came home, and my periods came back. I was glad to see them, though I’ve never been one to embrace my menstrual cycle by singing to the moon, probably because the act of menstruating for me is linked strongly to my severe endometriosis.
Like most women with endometriosis, my diagnosis took years, because whenever I told a GP – which I did every few years – that my periods were painful, I was told, “that’s normal”, even while I was given prescription-strength painkillers, again and again. Pain is not normal, and nor is endometriosis. But periods are, and so are all sorts of reasons your period hasn’t arrived. So if you asked me why your period is late, I would say: ask your doctor. And if you don’t get a good answer, ask again, and again, until you do.
