London — When former banker Ivy Huq Russell struggled to raise funds for her business - an app designed to empower women in Bangladesh by sharing expert health advice - it was a female investor who came to her aid.
That support is part of a wider trend for investors to back businesses that seek to reduce gender inequality while generating financial returns, known as "gender lens" or "gender-smart" investing.
"She invested believing in the business, of course, but also understanding how difficult it is as a mum, as a wife, as women that sometimes we need a little push," Russell told the Thomson Reuters Foundation of her backer.
Today the app, called Maya, is thriving, answering thousands of questions a day from users in India, Bangladesh and Saudi Arabia.
Although still in its infancy, gender lens investing is rapidly growing in popularity, having expanded well beyond its roots in microfinance to include venture capital, private equity, bonds and other forms of investment.
The definition is broad and crosses sectors - it could mean investing in women-led businesses, ones that sell products or services to help women and girls or those with good supply chain and workplace gender policies.
The value of private funds with a gender focus reached $2.2 billion in the year to July 2018, 73 percent higher than the same period in 2016/17, according to a report by Wharton business school and consultancy Catalyst at Large.
Big banks, such as Bank of America Merrill Lynch and UBS, have thrown their weight behind it.
Supporters believe there is not only a pressing moral imperative to promote gender equality, but an economic one - according to McKinsey, gender equality could add up to $28 trillion to the world's output by 2050.
"I'm a fundamental believer that backing women is not just the right thing to do - it's the smart thing to do," said Suzanne Biegel, a prominent gender lens investor and founder of Catalyst at Large.
"My portfolio and a lot of people's portfolios have proven that out," she said.
Biegel invests in a range of funds and businesses. Some of these are social enterprises, which have clear social impact objectives, and others are purely commercial ventures.
Social enterprises are often the benefactors of gender lens investment. But this association can hold gender lens investing back, because of a stigma that exists within the investment community towards social enterprises, Biegel said.
There is an assumption that social enterprises that help women are not profitable.
"People will often confuse things - when they hear a business is good for women, it must be a social enterprise," she said.
"The challenge sometimes is by labelling something a social enterprise that people will discount the value of it from an investment standpoint," she said.
Because the financial industry is male dominated, there have been fears that gender lens investing could become a box-ticking exercise for companies trying to make themselves look good.
"You could argue though that gender-lens investing is more susceptible to the risk of impact washing than perhaps other sectors," said Sapna Shah, director of strategy at Global Impact Investing Network, which promotes impact investing.
"For example, it would be easy to invest in a company that happened to have some female leadership and retroactively claim a gender-lens motivation without evaluating whether the investment had a positive additional impact," she said.
To avoid this situation the industry must be rigorous in measuring the outcomes of these investments, she added.
Russell has raised $450,000 in equity investment overall and $180,000 in grants, the majority of which she believes were unrelated to gender. She believes investors will only back companies that make financial sense for them.
"Overall the VC (venture capital) world and private equity world wouldn't just throw money until they see money in it as well," she said.
"Because I'm a woman, and I have a personal story, is a good starting point, but it's not enough."
As gender lens investment gains momentum, the industry will be eagerly awaiting results.
Investment research company Morningstar analysed the performance of 10 gender focused funds in North America and Europe that invest in large cap companies. It found seven of these funds performed in the top quartiles of their categories.
"The initial numbers are encouraging but it is still fairly early," said Madison Sargis, associate director of quantitative research at Morningstar.
While gender lens investing is still young, supporters believe a forthcoming shift of money into the hands of women and millennials in the West will be a boon.
The private wealth held by women grew from $34 trillion to $51 trillion between 2010 and 2015 according to research from the Boston Consulting Group, which forecasts they will hold about a third of the world's wealth, $72 trillion, by 2020.
"When you think about who is controlling the wealth, the biggest transition of wealth is going into women," said Sarah Chen, co-founder and managing partner of the Billion Dollar Fund for Women, a global consortium of venture funds.
"The millennial generation, as well as women, want to see more diversity, they want to be inclusive in the work they do."
- Reporting by Sarah Shearman @Shearmans