Conception is the process of becoming pregnant, from the time when sperm travels up through the vagina into the uterus and implants itself in the ovum, aka egg, found in the fallopian tube. Timing, reproductive health, and semen quality can all affect a couple's ability to conceive. We all learned about this initial stage of development for human growth in health class, yet many myths surround the concept of conception.
Read on for answers to pressing questions, like: Does marijuana make sperm do the backstroke? Do tighty whities hurt your chances of conceiving? And finally, we'll address the biggest myth of all: Ovulation is the best time to copulate if you're trying to procreate. But first, let's have a little SexEd refresher.
The first day of a woman’s period kicks off her (normally) 28-day menstrual cycle. Ovulation occurs halfway through, around day 14. During ovulation, the ovary releases one mature egg, which then travels down one of the fallopian tubes. That egg has 12-24 hours to be fertilized. Sperm travels through layers of cervical mucus, past the uterus, and into the fallopian tubes. A woman's immune system acts as a bouncer, only allowing a few hundred of the millions of ejaculated sperm anywhere close to the egg.
It takes about 24 hours for a sperm cell to fertilize an egg. (Fun fact: An egg is the largest cell in a human body, while a sperm is the smallest human body cell.) Once the winning sperm penetrates the egg, the cells start dividing. Three or four days after fertilization, the egg moves from the fallopian tube to cushier digs in the uterus, where it attaches to the lining (aka endometrium) in a process known as implantation. The cells keep dividing—some turn into the placenta, while others become the embryo. Estrogen and progesterone hormones help thicken the uterine lining and signal "we've got an embryo!" so the body won't produce a period and shed the uterus lining. You know the rest of the story: Week 5: Heartbeat. Week 8: Official fetus status, half an inch long and growing. Week 40: Boom, full-term baby. Now, let's move on to the misconceptions that some people may have about this whole sperm + egg = baby process.
Practice makes perfect? Not so much. Some people think that having sex three times a day during ovulation will help their chances of conceiving, but that can actually lower sperm count over time. Once a day in the week leading up to ovulation (the week after your period) is plenty.
The narrative around conception makes it sound like the woman's reproductive organs are passive participants in fertilization, waiting for the fastest, fittest "sperm to swim through a hailstorm of challenges to perpetuate life" as one Aeon article puts it. However, just as woman didn't come from a man's rib, it turns out that the uterus muscles are actually doing most of the heavy lifting, coaxing the sperm towards the egg. Instead of a swim meet, it's more like an American Ninja Warrior obstacle course.
"Many sperm do not even make it into the neck of the womb (cervix). Acid conditions in the vagina are hostile and sperm do not survive there for long. Passing through the cervix, many sperm that escape the vagina become ensnared in mucus. Any with physical deformities are trapped. Moreover, hundreds of thousands of sperm migrate into side-channels, called crypts, where they can be stored for several days. Relatively few sperm travel directly though the womb cavity, and numbers are further reduced during entry into the oviduct. Once in the oviduct, sperm are temporarily bound to the inner surface, and only some are released and allowed to approach the egg." according to Aeon.
Post-coital techniques like elevating your hips on a stack of pillows, standing on your head, hanging upside down, or lying down for 10 minutes after sex do not increase the chance of conception. Same goes for sexual positions—one is not more effective than another (as far as baby-making goes, orgasm-making is another story, wink wink).
Far from it. Once you've been preggo, that just proves you have the ability to become pregnant, which is a great sign as far as fertility goes. OB/GYN Steven Goldstein backs me up on this one, stating that, "Once you get pregnant, your chances of repeating will be more successful. Anytime there’s proven fertility, the odds are in your favor the next go around."
There's a reason that testes have their own little sack—because spermies like it to be slightly cooler than body temp. Increases in scrotal skin temperature are associated with a substantial reduction in sperm concentration. However, they have literally studied whether briefs make the scrotum warmer than boxers do and the difference was not significant.
It turns out that sitting is actually worse than wearing briefs when it comes to testes temperature. One study found that a prolonged sedentary position that "elevates the scrotal temperature may be a risk factor for low sperm concentration." So instead of changing your man's underwear, change his sedentary lifestyle.
Does imbibing in the devil's lettuce lead to slower swimmers? Does marijuana impact sperm count? A 2018 study found quite the opposite. Men who reported using cannabis had "significantly higher" sperm counts than men who had never toked.
Little is known about the reproductive effects of paternal cannabis exposure. The Harvard Gazette notes that "Previous studies on marijuana have suggested that it is associated with negative effects on male reproductive health, but most of those studies had focused on animal models or on men with histories of drug abuse." As one review puts it, "Despite marijuana use being implicated to cause reduced libido, gynecomastia, and erectile disorders, no properly controlled study has been performed in humans to substantiate these speculations." Newsweek says, "Studies investigating the link between human fertility and using cannabis are small, not randomized, and retrospective." Parents.com says "Clinical trials, the highest quality study type producing the most reliable results, have not yet been performed and would provide further clarification."
Long story short, we don't know. But we do know that medications can affect sperm count, and that cigarette smoking can reduce the quality of semen. Since research is inconclusive at best and contradictory at worst, it's best to take a better-safe-than-sorry approach when it comes to cannabis. It takes sperm and eggs about 90 days to mature, so both parents should layoff the ganja for a few months in preparation for conception.
Many women think that the optimal fertile period during their menstrual cycle is when they are ovulating. Technically your body does have to release the egg to be able to conceive, so this notion isn't incorrect, it's just misleading. The egg only has a 12-24 hour window for fertilization, but sperm can survive in the mucus for up to five days, so wouldn't it be best to have some sperm waiting for the egg to arrive? In fact, according to The Royal Women's Hospital, "the best time to attempt a pregnancy is in the three to six days leading up to and including ovulation."
A 2013 study that was published in Human Reproduction calculated the probabilities of getting pregnant on any given day of the menstrual cycle. On the first day of your period, the odds are nearly zilch. Odds of becoming pregnant increase steadily until Day 14 (just before ovulation), at which point they drop again. Calculate your fertile window here.