Conceiving a child can be difficult and issues of fertility can be compounded by questions about sex. In a new study, clinician-researchers from the Center for Reproductive Medicine of Shengjing Hosptial hope to ease those concerns with some sound — and quite welcome — advice. They argue that while men have previously been advised to have less sex to increase the chances of pregnancy, the opposite is true. For healthier sperm, there needs to be sex.

“Our data indicate that couples with relatively normal semen parameters should have frequent sex around the ovulation period,” study co-author Dr. Da Li explained Monday. “This could make all the difference to their efforts to start a family.”

In Molecular and Cellular Proteomics, Li and co-author Dr. XiuXia Wang explain that previous studies suggested that semen produced within three hours of a man’s most recent ejaculation were faster and more motile than those produced by men who abstain for several days between ejaculations. This finding goes against the advice from some fertility clinics that abstinence leads to better sperm but also didn’t go far enough to say whether this sperm could improve couples’ chances of becoming pregnant.

The advice regarding how often couples — both those who are planning to use IVF and those who don’t — should have sex varies. Despite headlines like “Abstinence Makes Weak Sperm Grow Stronger,” Dr. Laura Dodge, an instructor in reproductive biology at Beth Israel Deaconess Medical Center and the Harvard T.H. Chan School of Public Health, tells Inverse that couples with normal semen parameters are usually advised to have sex every other day.

University of Sheffield professor of andrology Allan Pacey, Ph.D., who researches male infertility, tells Inverse that regimenting sex can “itself be stressful.” He continues: “I would much rather that couples had a healthy sex life and by having sex every two or three days, they are bound to hit the right time more or less most of the time.” But he notes that this advice may not be as helpful for couples who are trying to maximize sperm quality prior to an assisted conception treatment.

sperm
Here are some sperm.

In the first experiment conducted by Li and Wang, sperm from donors who had either abstained from sex for several days or just a few hours were examined by mass spectrometry. By evaluating the molecular differences between the two samples, the scientists discovered that, overall, the sperm in the abstinence group was more vulnerable to DNA damage, which decreases the sperm’s chances of forming a successful embryo.

It turns out that the longer a sperm exists, the more changes there are to the proteins that influence how it moves and metabolizes. Sperm that emerge after shorter abstinence periods are able to move much faster. Quick, mobile sperm is good for couples who want kids because they’re better equipped to move through the female reproductive tract — or through water, if a couple is using in vitro fertilization — to reach the egg.

IVF chart
Semen produced after a short abstinence period of less than three hours increases a couple's chances of successful IVF.

To figure out whether quick, post-sex sperm actually means more babies being born, Li and Wang examined the sperm of 250 men preparing for in vitro fertilization at a fertility clinic. While a control group was provided semen ejaculated after several days of abstinence, the experimental group only abstained for three hours max before providing the sperm. Then, doctors at the clinic went on as usual and used the sperm to generate and then implant embryos.

In the end, the sperm that emerged after shorter abstinence periods increased couple’s chances of a baby by 30 percent. That’s a big deal for the thousands of couples who rely on IVF to start a family: In 2012 in the United States alone, more than 61,000 babies were conceived via IVF.

But Dodge warns that this study isn’t without its important caveats. While she thinks the results are reasonable, Dodge notes that the study is small, and it’s unclear whether there are factors other than abstinence time that affect the incidence of live birth. Because the results are from an infertile population, these recommendations also “may or may not apply to a general population attempting conception without assistance.”

“Bottom line, this study hasn’t convinced me that we should change our pre-conception counseling,” says Dodge. “I think it’s most important for conception for couples to be aware of their fertile window, but for those who are struggling to conceive after having sex every other day, it really can’t hurt to try every day.”