When Nicola Andrews became pregnant in 2017, she was surprised to discover that she felt better than she had in years.
Although she suffered from severe morning sickness, her other health problems - the overwhelming fatigue, blurred vision and weird tingling sensations in her limbs, which had blighted her daily life before pregnancy - entirely vanished.
Nicola, 33, a membership services officer for a children's charity, from Newtownabbey, Northern Ireland, has multiple sclerosis - a neurological disease in which the immune system attacks the nervous system, causing symptoms including pain, spasms and problems with mobility, balance and vision. What she experienced during pregnancy - an easing, or cessation, of her symptoms - is not unusual.
In fact, it's common; for many women pregnancy puts MS into remission. Studies have shown that, in the third trimester, there is around an 80 per cent decrease in MS relapses. While scientists have long known that pregnancy dampens down the immune system, so a woman's body doesn't reject the baby as a foreign object, and that this can alleviate the symptoms of several auto-immune conditions, nobody has yet discovered how or why.
Now, for the first time, an MS Society-funded study at Oxford University will attempt to find some answers and harness the power of pregnancy in order to develop new and better treatments.
"In MS, immune cells attack the brain and spinal cord," explains immunologist Prof Lars Fugger, who is leading the project at the Oxford Centre for Neuroinflammation.
"Many of the current drugs offered to patients are designed to suppress the immune system, but they often have serious side effects and patients can catch infections.
During pregnancy, women with MS find that their disease is reduced, even after stopping their medications, which suggests that their bodies are capable of suppressing disease directly - and that happens without side effects," he says.
"We want to identify what specifically drives this reduced disease. Once we have identified these targets, we hope to be able to either design new drugs or to repurpose drugs already used for other diseases, which may offer protection with fewer side effects."
The Oxford University team also wants to gain more general knowledge about pregnancy and MS, as women are often diagnosed at the time in life when they want to start a family.
The actress Selma Blair, 46, is one of the more high-profile patients with MS. Blair, who went to the Oscars using a walking stick, was making her first public appearance since her diagnosis last October.
"Although symptoms of MS are frequently reduced during pregnancy, patients often suffer relapses following birth. The combination of a new baby and a major relapse is a very difficult situation, and it is important that we understand why this happens, so that we cannot only inform patients of the risks involved but also design treatment strategies that could help prevent this," adds Prof Fugger.
His research, he explains, will isolate the cells of the immune system and examine them at a single cell level in order to identify the gene expression - the mechanisms - by which the immune system modulates disease during pregnancy.
Samples have already been collected from a cohort of female MS patients and from healthy control subjects, who donated blood before pregnancy, in each trimester and after giving birth.
"Previous studies have grouped the cells into generic populations, which has missed many important subtleties. We will examine each cell independently, which will allow us to see all the small and yet potentially critical changes that occur at an individual level."
Dr Susan Kohlhaas, director of research at the MS Society, says she has heard stories of women who were, in the past, advised not to have children for fear of making their condition worse.
"We now know that there's no long-term impact on MS from pregnancy, or impact on its trajectory, so women shouldn't worry about that," she insists.
Nicola was diagnosed with MS in Dec 2014 - four months before her wedding to husband Robert. Symptoms included blurred vision, a numb face, and pins and needles in her legs. She worried whether it was safe to have children.
"I was scared," she recalls. "There isn't a lot of information out there. But other women, my neurologist and MS nurse reassured me. The main complication was that I had to come off my medication three months before conceiving, as techfidera [a disease modifying drug for relapsing-remitting MS] can't be taken during pregnancy. That rather took the spontaneity out of it. Fortunately, I got pregnant straight way."
The improvement to her MS symptoms was impossible to ignore: "I felt so much better. Yes, I was tired in pregnancy, like everyone, but I no longer had the MS fatigue, which is like having concrete blocks strapped to your feet while you try to walk. You can't think, or move, or talk. Pregnancy tiredness is relieved by a good sleep; fatigue isn't."
One theory is that pregnancy's protective effect might have something to do with the way the particular balance of female hormones changes the way immune system cells behave - but Prof Fugger won't speculate.
"We simply don't know," he says. "We are doing this research in a hypothesis-free, agnostic way. There is no evidence that it's sex hormone specific."
Whatever the academics uncover, it certainly won't be as simple as prescribing oestrogen and progesterone to MS patients and expecting an improvement. What little research that has been done in this area has not found a protective effect from either the contraceptive pill or HRT, or a significant menopausal impact.
But we do know that relapsing-remitting MS now affects three times as many women as men - again, doctors aren't sure why.Prof Fugger's team hope that their research can be used to develop treatments for men as well as women, and for other auto-immune diseases, too.
"Similar regulation of disease is also observed in pregnancy in rheumatoid arthritis, uveitis, and psoriasis, suggesting there are pathways common to multiple autoimmune diseases. So, finding treatments that regulate disease in MS patients may have a far wider application," he says.
The MS Society believes that with research, MS can be stopped. They're working with autoimmune charities, JDRS (the type 1 diabetes charity) and Versus Arthritis, to understand the common mechanisms of these conditions - and hopefully develop prevention strategies.
Nicola has not had a relapse since son Alexander, now four months old, was born - although she says her fatigue has flared up a little. She is now back on medication, which means she can't breastfeed. But an MRI scan performed a month after she gave birth revealed no active lesions on her brain or spinal cord, proving conclusively that pregnancy had put her MS into remission.
"Every MRI I've had before showed new lesions and new disease activity, even while I was taking my drug," she says. "So this was amazing. I know not all women are so well when they're pregnant, but I definitely think there's something in a treatment based on its protective effects. I'd like to have another baby, and I don't want to leave it too long in case my MS gets worse, but not yet. Having a child when you have MS is a big decision."
What is MS?
Multiple sclerosis is a neurological disease in which the immune system attacks the nervous system.
Symptoms include pain, spasms and problems with mobility, balance and vision.
Pregnancy has been shown to put MS into remission.