When it comes to conceiving, couples are bombarded with advice on what they can do to boost their chances.
Turns out one of the easiest things they can do is change their diet, two Harvard nutrition professors claimed in a book which has been a top seller for a decade.
The so-called 'Fertility Diet', which was published 10 years ago, is based on incorporating vegetables and whole-fat dairy - and cutting out red meats and trans fat - to improve ovulation.
There are even certain foods that men can eat to increase their semen quality.
The research has been contentious ever since, with many not believing that diet has any link to the chances of getting pregnant.
DailyMail.com spoke to an infertility and prenatal dietitian, who says that a lot of the diet's success depends on a woman's age, when she starts following the diet and if her partner is also adhering to it.
Lauren Manaker, an infertility and prenatal dietitian, told DailyMail.com that a fertility diet can be beneficial depending on a woman's age and when she begins following it (file image)
The original fertility diet, created by Drs Jorge Chavarro and Walter Willett of the Harvard School of Public Health, was based on the Nurses' Health Study, which investigated the risk factors for chronic diseases in women.
They looked at more than 18,000 women who were trying to conceive, and found that changing the quality of their diets reduced infertility risk in those with ovulation problems.
They said this helps increase ovulation and improve chances of getting pregnant.
Experts say that it can be helpful - in certain instances.
'It shouldn't be an additional expense or effort where you're spending thousands of dollar to buy every single thing it tell you to eat,' Lauren Manaker, an infertility and prenatal dietitian, told DailyMail.com.
'Try to follow at least five. Pick some interventions and see how it works.'
Additionally, many other diets follow the same principles as the fertility diet and can be just as successful.
A 2018 Greek study found that women who followed a Mediterranean diet had a greater success rate of becoming pregnant or giving birth after undergoing in-vitro fertilization.
THE 10 STEPS OF THE FERTILITY DIET
1) Cut out trans fats
2) Consume more unsaturated vegetable oils
3) Incorporate more vegetable protein and less animal protein
4) Eat slowly-digested carbohydrates
5) Choose full-fat dairy over low-fat products
6) Take a multivitamin that contains folic acid and other B vitamins
7) Up iron intake either from foods or from supplements
8) Cut out soda and drink plenty of water. Caffeine is also allowed
9) Achieve a healthy body mass index
10) Boost fitness levels
Dairy products such as milk, cheese and yogurt are allowed, but in moderation.
'Many of these diets have the same components, lots of fruits and vegetables or seafood,' Manaker said.
'It can only help as opposed to eating a diet high in processed and fried foods.'
In some cases, it could be that the diet helps with weight loss, which is why a woman is struggling to pregnant.
A 2008 study looked at BMI and found that for every point a woman's BMI increased after 29 (classified as overweight/obese), her chances of conceiving decreased by four percent compared to a woman with a normal BMI of 25.
And a 2017 Iranian study looked at women with polycystic ovary syndrome - a hormonal disorder that causes enlarged ovaries with small cysts - who followed the DASH diet, designed to lower blood pressure.
Women who followed the diet for 12 weeks had improved metabolic profiles and BMIs, which helped improve fertility.
'Everybody's body is different and weight can play a role in hormonal imbalance,' said Manaker.
'So, if someone lose a few pounds, that could be make or break. In some cases, a woman can lose weight but it's a egg quality issue so you have to look at it on a case-by-case basis.'
She adds, however, that not all of the emphasis should be on how well the woman is eating.
'I feel that a lot of focus is on the woman's diet and lifestyle and we're finding more and more that men's role may be just as important,' Manaker said.
She says that - just as women are told to stop smoking, cut back on caffeine and change their diets - men should do the same.
Men can eat foods such as salmon, high in omega-3 fatty acids. DHA, a member of the omega-3 family, has been found in high concentrations in sperm, showing that the molecules are important in promoting sperm cell viability.
Another food is dark chocolate, which contains an amino acid proven to increase sperm count, sperm motility and semen volume.
'Women can't be expected to carry that burden alone so men should be look at to make these changes as well,' Manaker said.
She also adds that age can be a factor in how successful the diet is.
'Diet helping to reach this goal is much different in someone who is 25 compared to 45,' Manaker said. 'A lot of these studies that look at fertility and diet don't look at women who are above 40, and obviously fertility decreases as you age.'
Something else to consider is when couples are starting these diets. Manaker says it needs to be at least three months before trying to conceive.
'I've had couples come to me and say: "I'm starting IVF tomorrow, should I start eating vegetables now?" and I go: "I can't help you",' she said.
Manaker explains that this is because sperm takes about two months to be created and that eggs need 90 days to mature.
Therefore, the sperm and eggs need time to receive the effects of the foods the couples are eating.
What Manaker tells all her clients is, before any lifestyle changes are made, to consult their doctor.
'People might see foods or supplements promoted on Instagram by celebrities and they're not safe, not regulated and the celebrities are not trained to look at the research,' she said.
'A doctor needs to know what couples are doing or using, otherwise they can't help.'