After Elizabeth Roberts had her two kids, the 39-year-old knew she wanted to help someone else build a family. Having watched a friend volunteer to be a surrogate, Roberts signed herself up in 2016.

The Halifax nurse filled out an online application for one of the biggest surrogacy agencies in the country, and within days, her profile was live.

"I didn't quite understand what I was sinking my teeth into. I just knew that I wanted to help people," Roberts said.

In the years since, Roberts has been a surrogate twice. And while her pregnancies have been relatively uneventful, she is now preparing for a hysterectomy, which she believes is because of her back-to-back pregnancies.

Dr. John Kingdom, a high-risk obstetrician at Toronto's Mount Sinai Hospital and professor at the University of Toronto, said it's possible that Roberts's complications could have been caused by having pregnancies in quick succession.

But he's even more concerned that Canada does not have mandatory wait times for surrogacies. He said that leaves women like Roberts vulnerable to manipulation.

"I think we should recognize that surrogates are altruistic, kind people who are at risk of power imbalances," Kingdom said.

'Like online dating for surrogacy'

Roberts said as soon as her profile went live in 2016, she was flooded by parent profiles and it broke her heart.

"It was like online dating for surrogacy," she said. "There are so many intended parents out there and only so many surrogates."

Roberts connected with one couple right away, prepared her body with painful progesterone injections and estrogen patches and hoped for the best.

"I had put a lot of pressure on myself, because literally all their eggs were in my basket. And I was just hoping that my basket would hold onto them."

Two-time surrogate Elizabeth Roberts said there needs to be better medical standards for surrogates to prevent women from pursuing back-to-back pregnancies while they are emotionally vulnerable after giving birth. (Steve Lawrence/CBC)

The embryo transplant worked, and nine months later she delivered the couple's baby girl. Roberts remembers the birth like it was yesterday.

She recalls "looking over and seeing the parents hold their daughter, and the dad looked up at me and he just had tears streaming down his face, and he just said, 'Thank you.' Any questions that I had ever had through the entire journey just disappeared in that moment."

CBC News spoke with dozens of surrogates as part of an exclusive investigation, and nearly every woman described the intense emotional high they experienced right after giving birth to surrogacy babies, some describing it as addictive.

"I think that is the thing that you're searching for when you go into this," Roberts said. "We've done this huge, incredible, amazing thing — what are we going to do now? And so I knew right away that… I was going to have to do it again."

Surrogates say they're 'hounded' to do it again

During CBC's three-month investigation into surrogacy, multiple women said their agency sent them new, heart-wrenching parent profiles within days of giving birth. Some of the women said they felt "hounded" to commit to a new couple right away.

The demand for surrogates in Canada far outweighs the number of women willing to carry a baby for someone else, which can cause women to feel pressured to commit to subsequent pregnancies. And there's a financial imperative for the agency — every couple the company connects to a surrogate represents thousands of dollars of revenue from consulting fees.

One woman, who CBC has agreed not to identify because she fears backlash from the surrogacy community, said she delivered one surrogate baby and was pregnant with another less than four months later.

The first birth ended in a C-section, and within two months she was taking hormone injections to prepare her body for another round of in vitro fertilization (IVF). The second pregnancy ended in twins for an American father less than a year later.

She said she was initially shocked by the tight turnaround, but it didn't really make her nervous.

"Honestly, I was OK. The dad was OK. Clinics were on board," she said. "You know, there was no forcing matters of any sort."

CBC spoke to another woman who pursued surrogacy after having three children of her own. She has given birth to three babies through surrogacy since 2016, and was pregnant with a fourth that ended in a miscarriage. She is currently pursuing her fifth surrogacy in under four years.

'A lot of surrogates feel lost'

Roberts was transferred with an embryo for a second couple six months after the first surrogate birth, and delivered the second surrogate baby nine months later.

Reflecting on her decision to pursue the second surrogacy so quickly, she said the speed between pregnancies didn't concern her much at the time. But she now admits she was in an emotionally vulnerable state in the initial weeks after giving birth.

"I think a lot of surrogates feel lost. I know I felt lost afterwards," said Roberts. "I didn't know what else to do."

In the period leading up to her second surrogate pregnancy, Roberts said neither the doctors overseeing her care nor anyone from the surrogacy industry questioned the quick timing or warned her of any risks that could come from a back-to-back pregnancy.

While she said she never felt direct pressure from the parents, she believes she could have benefitted from someone who asked tough questions about why she was committing to another pregnancy so soon.

She doubts it would have changed her mind, but she said her own internal pressure should have been challenged.

"I didn't want to waste anybody's time or money. I wanted to make sure that we had a result," she said. "I could have said, 'No, I'm done.' I didn't want to. I kept telling the mom, 'It's not over until this baby comes out, until I have your baby.' I was bound and determined to help this family."

While the pregnancy went off without a hitch, the second surrogacy birth left Roberts with severe physical complications and she will need to undergo a hysterectomy. As she waits for the surgery, she's often in so much pain she takes painkillers to help her get through the day.

"I think that every single surrogate at some point in their journey questions what they're doing," said Roberts. "I think we are a certain brand of crazy, to put it kindly, but we do this because we want to help, and it is worth every second of it."

Doctor says surrogates are 'vulnerable'

Kingdom said any IVF pregnancy is complicated right from the start, and it's even more risky for surrogates, for a variety of reasons.

"IVF is an unnatural mode of conception," he said. Surrogates are being implanted with genetic material that is completely foreign to their body, and this can cause higher-risk pregnancies and potential complications.

Dr. John Kingdom, a high risk obstetrician, says the lack of medical standards for surrogacies is leaving women vulnerable and open to risk. (Sue Goodspeed/CBC)

Kingdom said the risks of IVF are compounded for surrogates because these women are often older, and since they've likely had multiple births, there is a greater chance they've had at least one C-section.

General guidelines from the Society of Obstetrics and Gynecologists suggest women should wait a minimum of six months after a birth before embarking on another pregnancy — longer if the previous pregnancy ended in a C-section. However, the society does not establish mandatory guidelines specific to surrogate pregnancies.

Since most surrogacies are managed through the private fertility industry, Kingdom said there should be mandatory pre-pregnancy counselling built into the process.

Counselling might result "in a decision not to be a surrogate, or to delay it for further investigations or to reflect more carefully on whether they really want to embark on those risks," said Kingdom. "That's what informed choice is, and really, every woman in this country deserves a really good, informed choice."

Health Canada is responsible for administering and enforcing the Assisted Human Reproduction Act, the legislation that governs surrogacy. The agency says the AHRA does not provide the authority to prescribe the amount of time a surrogate must wait between giving birth and having an embryo transfer.

Determining whether a woman is medically fit to undergo a transfer is a medical decision, which Health Canada says is regulated by the provinces and territories.

Surrogates aren't 'breed mares'

Dr. Tom Hannam, the lead doctor and founder of Hannam Fertility in Toronto, said in the absence of a national medical standard for surrogacy pregnancies, his clinic has established its own standard of a nine- to 10-month wait period between a surrogate birth and a subsequent embryo transfer.

"If you were going to have shorter wait times, it would be incumbent on you as a clinician doing the extra work with the individuals involved to make sure that was really the right choice for everyone involved," Hannam said.

"Choosing to get pregnant again just four months after that is a big choice — one that is being made with a series of choices all at the same time. Sometimes a pause is the more appropriate course of action."

As Roberts awaits her surgery this summer, she's advocating that surrogates become better informed about the risks of back-to-back pregnancies.

"As unfortunate as the term may sound, surrogacy is an industry," Roberts said. "It's insensitive not to consider what the surrogates go through. They're not breed mares — we're people."

Send tips on this story to chelsea.gomez@cbc.ca or call 416-475-5778