Rob and Helen came to my clinic 18 months after throwing away Helen’s contraceptive pills. They were awkward with embarrassment as they took their seats. ‘We’ve been trying for a baby for ages,’ Rob began, then hesitated, but Helen finished the sentence: ‘We’re starting to think there’s something wrong.’ He was a chef: tall and slightly overweight, with silvering hair and anxious eyes. She was an assistant at a nursery: slim with bobbed red hair and doll-like, porcelain-white cheeks. ‘I don’t know if we need IVF?’ asked Helen, spinning her wedding ring with the fingers of her right hand, ‘but at thirty-seven I’m told we should hurry up.’
I asked about family history. Helen was one of three children, didn’t know of any problems that ran in her family, and both her brother and her sister already had children of their own. Rob was also one of three: though his brother had a daughter, she’d been conceived with the help of IVF. On average, couples who have regular unprotected sex have about a 20 per cent chance of conceiving within a month, 70 per cent chance of conceiving within six months, and 85 per cent chance of conceiving within a year. It’s for that reason that doctors prefer to wait at least a year before initiating infertility tests. The first tests to be carried out are the most straightforward: for Rob, two semen samples sent in at least a month apart after a few days’ abstinence, and for Helen, blood tests at two separate points in her menstrual cycle to assess whether she was ovulating regularly. The semen samples are trickiest to arrange; they have to be delivered to the lab, which is only open at certain hours, within an hour of ejaculation. ‘What ... these?’ said Rob when I handed him the specimen tubes. ‘They don’t give you much ... to aim for.’ How he went about obtaining the samples we left undiscussed. Helen laughed, dissolving the tension in the room at last. ‘What are you trying to say about your equipment?’ she said, elbowing him.
Helen needed a blood test on the third or fourth day after her next period began, followed by another one seven days before the following period was due. The first test gives an idea of whether the two hormones that coordinate ovulation – ‘luteinizing hormone’ and ‘follicle-stimulating hormone’ – stand in the right ratios to one another and to levels of estrogen. The second test gives an idea of whether the ovary is creating enough progesterone – the hormone that prepares the womb for pregnancy – to suggest she had ovulated. Helen drew her diary from her bag, where all her periods for the past year had been plotted out on a grid. ‘This is my menstrual map,’ she said grimly; ‘a map of disappointment.’ We picked out the days she’d need blood tests, and fixed the appointments.
When I met her next she came alone. After taking the blood samples she rolled down her sleeve and paused. ‘You know the worst of it?’ she said. ‘It’s what it’s done to our sex life ... I mean, it’s difficult to feel romantic, or desirable, when all you’re thinking about is ovulation and conception.’
‘Some people don’t conceive until they get their appointment through for the fertility clinic,’ I said, ‘that’s when they stop worrying about it. Don’t make it a trial, or something to get stressed about.’
‘That’s just it,’ she said. ‘Before, I hardly ever had an orgasm with sex. Now, I never do. Do you think that’s a problem?’
*
The nerve that coordinates orgasm, called ‘pudendal’, has an almost identical course in men and women. Its name comes from the Latin, pudere, to be ashamed, as if we’re still cowering in the Garden of Eden, trembling behind fig leaves. The pudenda might be comic, absurd or even embarrassing, but never shameful: without our parents’ pudendal nerves, after all, few of us would be here. People can be reluctant or embarrassed to discuss aspects of conception, sex and sexuality, but as a doctor it’s unavoidable; you can’t work with human bodies for long without having to talk about them.
Whether folded in foreskin, or desensitized by circumcision, the pudendal nerve in men branches through the skin of the glans penis, and in women through the clitoris. Those nerves coalesce into bundles that run down the back of each corpus cavernosum – the ‘cavernous bodies’ present in both sexes, which stiffen through being engorged with blood, but which were once thought to be inflated by the pneuma, or spirit, of sexual desire. The nerve on each side then drops down into the penile or clitoral root and loops under the arch of the symphysis pubis of the pelvic bone – an angled Gothic arch in the male, and a rounder Roman arch in the female (with its smoother accommodations for a baby’s head, and its more dissipated scatter of nerves). It then tunnels deeper into the layers of muscle and sinew that support and give continence to the bladder, taking in out-branches that supply sensitivity to the skin between the thighs. It’s here that it slips under the prostate gland and seminal vesicles in men, which store and bathe the sperm that have migrated up from the testis, and the cervix and womb in women. Then it continues towards the spine, emerging into the pelvis between powerful muscles that cantilever the weight of the body into the legs.
The sacrum is a triangular bone at the base of the spine, perforated by holes like a priest’s censer. It is so called because it was once believed to be sacred: a reservoir of human essence – medieval Europeans thought that at resurrection their bodies would be reconstituted first from the sacrum, and that energies discharged from the sacrum were essential in the creation of new life. After twisting themselves through the tangle of the sacral plexus, pudendal nerve fibers slip through the sacrum’s perforations, and plug into the spinal cord.
Marcus Aurelius spoke of orgasms as the simple product of a timed duration of friction. Aristotle thought that the heat necessary for conception was generated by sex just as a fire can be ignited by rubbing two sticks. But of course the propagation of sexual tension is less predictable than those theories suggest; less a process of ignition than the interplay between storm clouds and an ionizing earth – the lightning flash of a two-way traffic between the mind and bodily physiology. In Western countries where surveys have been attempted it’s been reported that only a third of women regularly experience orgasm during intercourse, the reasons for this being both social and physical. The effect of drugs can play a part: antidepressants like Prozac and Seroxat, some of the most commonly prescribed drugs in the Western world, can so dampen the action of those nerve endings that orgasm becomes difficult to achieve for both men and women. Heroin can do the same, and, most famously, so can alcohol.
A mirroring tension builds between the nerves within the glans or clitoris and the answering plexus in the pelvis until some final, pivotal change provokes the climax. What the French called la petite mort can be seen on brain scans not as a darkening to oblivion, but as a ‘lighting up’ in the emotional core (cingulate gyrus), reward centers (nucleus accumbens), and hormonal regions (hypothalamus) of the brain. It’s those hormonal regions that in some animals actually provoke ovulation as a response to sex, just as Galen imagined, but in humans that’s not the case.
During orgasm, pulses of nerve stimulation ripple back out from the spinal cord to the prostate gland and seminal vesicles in men, and the cervix and vagina in women. In men they trigger the prostate, vas deferens and urethra to squeeze sperm and seminal fluid towards the penis in a series of clenching spasms, while coordinated reflexes shut the entrance to the bladder so that semen can go only one way – out. In women, those same ripples trigger convulsions in tiny glands around the urethra and anterior wall of the vagina – Skene’s glands – which push out a sort of female seminal fluid similar to the prostatic fluid expelled by men.
The outlets of Skene’s glands vary between women: on climax they may push a watery fluid out into the urethra as occurs in men, or directly into openings within the vagina – explaining why some women feel as if they ‘ejaculate’ on orgasm, while others do not. An Italian sexologist, Dr Emmanuele Jannini of L’Aquila University, believes that the area around the urethra on the anterior vaginal wall is a separate erogenous zone in some women, distinct from the clitoris. Like Ernst Gräfenberg, the New York sexologist whose initial ‘G’ gave the name to the ‘G-spot’, Jannini thinks that there are women who experience orgasms deeper in the vagina than others, as an accident of their pudendal nerve anatomy.
The vagina in health is acidic, something that helps keep it free of infection. Unfortunately, sperm prefer a neutral environment – neither acid nor alkaline – similar to that prevailing within the womb. The secretions from Skene’s glands and the prostate gland are alkaline, which suggests that they helpfully neutralize the acid environment of the vagina at the moment when sperm are released into it. The secretions from Bartholin’s glands, which lie at the posterior entrance to the vagina and become active much earlier in intercourse, are also alkaline and so do the same thing.
William Taylor wrote over two centuries ago, ‘so the poetic orgasm, when excited, glows but for a time’: in men, up to ten seconds; for women, orgasm can last double that. The pattern of female orgasm is different from that of the male: broader and slower to rise as well as fall away. There are several theories, none entirely convincing, which suggest how female orgasm might help in conception. One theory is that the longer duration of the female orgasm in women could give the cervix more time to pull in male seminal fluid, which may increase the likelihood of pregnancy, and could help sperm survive by neutralizing the natural acidity of the vagina. But there are others: by encouraging more sex; by secreting the hormone oxytocin from the brain (which may cause the womb to draw in fluid); even that female orgasms help in sexual selection – identifying men who are more likely to prioritize their women’s happiness as highly as their own.
*
A few weeks later I met Helen and Rob again. Rob’s semen analysis was normal: I ran through the parameters examined by the laboratory, translating the arid terminology of ‘motility’, ‘morphology’, ‘concentration’ and ‘consistency’. Helen’s hormone tests too had come back as I’d hoped: the LH and FSH were in appropriate proportion to one another, the estrogen as low as it should be early in the cycle. The progesterone level in her blood a week before her period was due suggested that she’d ovulated normally – there was no obvious reason they weren’t conceiving.
‘So the results are all very reassuring,’ I told them. ‘Rob, your tests are normal, and Helen, your ovaries are ovulating at the time in the month we’d expect them to.’
‘So what could be wrong?’ she asked.
‘Sometimes the tubes inside aren’t letting the sperm past for some reason, sometimes the immune system prevents the sperm and the egg coming together, often there’s nothing wrong at all.’
‘So what now?’
‘Now I write to the fertility clinic at the hospital, and you two try not to worry about it too much.’
Excerpted from "Adventures in Human Being: A Grand Tour from the Cranium to the Calcaneum" by Gavin Francis. Published by Basic Books, a division of the Perseus Books Group. Copyright 2015 by Gavin Francis. Reprinted with permission of the publisher. All rights reserved.
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