Lauren Burnham and Arie Luyendyk Jr. had sex for 18 days straight when trying to conceive. Is that the wrong approach?

Although Lauren Burnham and Arie Luyendyk Jr. are happily expecting twins, the Bachelor stars say they used "the wrong approach" to conception.

The couple, who married in 2019 after meeting on Season 22 of the reality show, shared in a Monday YouTube video that they had sex for 18 days straight when trying to conceive. "We're going to tell you how to make a baby!" Burnham, 29, the owner of Shades of Rose clothing line, said.

In May, the couple (who share 21-month-old daughter Alessi), experienced a miscarriage and waited to be medically cleared before trying again.

"Trying was fun," Luyendyk Jr., 39, admitted, with Burnham adding, "For a little while. It was fun until it wasn't." The couple decided to use daily ovulation strips, available OTC, to gauge Burnham's fertile period. Women are generally most fertile about six days before ovulation (when an egg is released for fertilization, which occurs about two weeks before menstruation begins) and one day after ovulation.

"And then it was like, every day, it seemed like a high fertility day," recalled Luyendyk Jr. "…It was like 18 days in a row." The couple admitted their approach may have not been scientifically sound. "So maybe for the first two weeks, we were just having fun," said Luyendyk Jr.

“In the beginning, we were just like, ‘We'll just have sex every day...'" he said, which Burnham called "the wrong approach" adding, "My doctor's like, 'Yo, you need to calm down.'" She said, "Arie's like, ‘No. I’m not on board for this. I’m worn out. He's like, 'This is just not fun anymore. Count me out.’ I got pissed."

Eventually, the couple decided to stop stressing ("We just kind of gave up," said Burnham) and had sex every other day for a period of five or six months, during which Burnham also took prenatal vitamins and an essential oil (her doctor dismissed the latter as effective), and in December, they became pregnant with twins (a boy and a girl).

While the baby-making journey can be equal parts fun and stressful, daily attempts are actually unnecessary, according to Dr. Christina Jung, a complex family planning fellow at the University of California, Los Angeles. "Every woman is different, but the days before ovulation are generally considered the fertile period," she tells Yahoo Life. Jung adds that an 18-day window of fertility is unlikely, noting that some ovulation tests can yield false-positive results due to certain medical conditions, irregular cycles or if tests are taken at varying times of day when results can fluctuate. "It's also possible that people may not interpret results correctly," she says.

Because sperm remains viable for roughly five days in the female reproductive tract, couples should have sex a few days before a woman releases an egg for fertilization, explains Jung. "Once that egg is released, it's only viable for about 12 to 24 hours — then the probability of pregnancy lowers."

Ovulation strips can help couples determine their fertile period by measuring luteinizing hormone (commonly referred to as LH) through a woman's urine, amounts of which surge before ovulation, according to Jung. "You want to pinpoint the window of ovulation — so if you will likely ovulate on Friday, maybe have sex on Wednesday," she said. "We also recommend keeping an ovulation diary and allowing two or three cycles to pass to collect historical data."

There are other low-cost methods of tracking ovulation, such as monitoring a woman's daily basal body temperature (per the Mayo Clinic, ovulation causes a small temperature spike so tracking that increase over time is one way to predict when ovulation occurs) and monitoring cervical mucus, a more meticulous approach of noting slight changes in cervical secretions around ovulation. "However, these methods are only useful if one has very regular cycles," says Jung.

If couples want to have sex every day, that's OK too and no conception method is fool-proof. "Sometimes couples can do everything 'right' and not get pregnant, while others use protection and still conceive," says Jung. "There's still much for scientists to learn but so far, these [principals] guide our caretaking."

Read more from Yahoo Life:

• Why the Rock loves raising girls: 'Every man wants a son, but every man needs a daughter'

• The CDC says in-person schooling can be done. Here's how.

• 'It's like a bingo game': Inside the world of leftover COVID-19 vaccines

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