When to have sex to conceive

The likelihood of getting pregnant is not always the same during the menstrual cycle, and so it is important to understand when the fertile window is. During the fertile window is when ovulation occurs, i.e., the time when the ovaries release an egg, after which fertilization of the egg (conception) can occur.^i,ii Ovulation occurs around day 14 or 15 of a "text-book" 28-day menstrual cycle, ^{iii,iv,v,vi,vii}

Consequently, because the sperm cells may be able to survive for five days and the egg lifespan in the fallopian tube is 24 hours, the fertile window spans—at most—from five days before ovulation to one day after.^viii,ix,x More clearly, the fertile window is approximately six days, on average, from day 9 to day 15 of a 28-day menstrual cycle.^xi,xii,xiii During that time, if sperm and egg meet, a fertilized egg (called a zygote) may result.

Studies have shown that scheduling intercourse during the fertile window—also referred to as timed intercourse—is more likely to result in pregnancy than untimed (spontaneous) sex.^xiv In one analysis of four randomized controlled trials, researchers showed having timed intercourse boosted a woman’s chance of getting pregnant by 35 percent.^xv

It is worth noting that cycle length and the fertile window vary considerably between women and can be variable in the same woman from month to month. This variability is higher in females with an irregular cycle than in those with regular cycles.^xvi In addition, studies have shown that many females believe that they know the correct timing of their menstrual cycle/fertile window, but after tracking their ovulation, they realize that their cycle predictions were incorrect.^xvii,xviii This suggests that many women will be having timed intercourse during the incorrect window.  

To help predict the fertile window, at home ovulation predictor kits (OPKs) can be used. Much like a home pregnancy test, an OPK can help take the guesswork out of trying to get pregnant. These are urine test kits with test strips that women can use at home to indicate the start of the luteinizing hormone (LH) surge. Many OPKs are used in conjunction with an app, to help improve accuracy of cycle monitoring over time. Most kits measure LH only, but some also measure estrogen metabolites (in general, estrone-3-glucuronide=E3G) found in urine.^{xix,xx,xxi,xxii,xxiii}

Typically, ovulation occurs around 36 hours (ranging between 24-48 hours) after the LH surge starts (or 10-12 hours after the LH peak). While these kits cannot definitively indicate when ovulation will occur, they provide a good idea of when it will happen, greatly helping attempts to get pregnant.^xxiv  It is worth noting that some people will have an LH surge but not release an egg. In these individuals, OPKs will indicate a surge, but the surge is not followed by ovulation.^xxv  

OPKs that measure both E3G and LH may be able to identify a rise in estrogen that could indicate the start of the fertile window. This estrogen increase typically occurs three days before the LH surge. As a result, OPKs that include E3G may be able to indicate the fertile window a few days earlier than LH-only kits.^xxvi In addition to OPKs, a woman’s basal body temperature will rise after ovulation. As such, many women also track their basal body temperature to help with determining the fertile window.  

For those trying to get pregnant at home, unprotected sex or home insemination is necessary. Unprotected sex means semen (containing sperm) is ejaculated into the vagina during the fertile window. In as little as 5-10 minutes, sperm can travel through the cervix, into the uterus, and to the fallopian tubes, moving towards the egg.^xxvii,xxviii Once there, if a mature egg (called a secondary or MII oocyte) is present, fertilization may occur.  

How often to have sex when trying for a baby

It is a common myth that having unprotected sex more often during the fertile window will result in a lower count or quality of ejaculated sperm, potentially leading to a decreased chance of conception.^xxix There is no data to support that more frequent sex lowers the chance of conception.^{xxx,xxxi,xxxii}

Evidence suggests that having unprotected sex regularly--daily or every other day--is equally likely to result in pregnancy during a given cycle and gives couples the highest chance of achieving pregnancy. In fact, the likelihood of pregnancy drops by 15 percent for couples who only have sex once weekly.^{xxxiii,xxxiv,xxxv,xxxvi}

Still, the American Society for Reproductive Medicine (ASRM) recommends that couples guide their own optimal sex frequency. Otherwise, there can be a negative impact on mental health, leading to reduced satisfaction and self-esteem, and potentially reducing the frequency of sex and thus the possibility of conceiving. Ultimately, couples should have sex at a rate that is most comfortable for them.^xxxvii

What is the best sex position for conception?

There is a common assumption that there is a best position for intercourse or that position matters when trying to conceive via unprotected sex, such as lying on one’s back, hips elevated, with legs in the air. No evidence exists to suggest that sexual position or maintaining a certain position after sex increases the likelihood of conception.

Sperm can make it past the cervix and uterus to the fallopian tubes in as little as 5-10 minutes. There are various myths about sexual positions or post-intercourse practice to improve the chance of conception. However, there is no scientific evidence to support that a specific sexual position during intercourse will affect the chance of conceiving. ^xxxviii Similarly, methods intended to keep semen inside the vagina for prolonged periods (e.g. lying flat or legs held up in the air) will not increase the chance of getting pregnant.^xxxix

How to optimize fertility through lifestyle

Even among individuals in good health, lifestyle factors can have an impact on fertility. Consequently, it can be helpful to make certain lifestyle changes to improve overall health and avoid potential fertility problems. In women, fertility rates are lower among individuals who are under- or overweight, as well as in those who smoke.  In terms of the effect of moderate alcohol or caffeine consumption on female fertility, the data is equivocal.^{xl,xli,xlii,xliii}

Current or past history of sexually transmitted infections (STIs) can lead to infertility, so it is critical to identify whether either partner has one. For example, pelvic inflammatory disease (PID) can obstruct the fallopian tubes, and epididymal infection can affect sperm production/maturation^xliv,xlv Consequently, the American Centers for Disease Control and Prevention (CDC) recommends STI testing (i.e.., chlamydia and gonorrhea) in all pregnant women younger than 25 and pregnant women over age 25 who believe they are high risk. All pregnant women should be tested for syphilis and human immunodeficiency virus (HIV) at their first prenatal visit.^xlvi

To protect fertility, exercise caution when using lubrication during sexual intercourse. The composition of some lubricants can reduce sperm motility, or block the cervix, thereby reducing the chance of conception.^xlvii For example, water-based lubricants, such as Astroglide, K-Y Jelly, and K-Y Touch, have been shown to decrease sperm motility, though it can take up to an hour for this to happen.^xlviii In contrast, mineral oil, canola oil, and hydroxyethylcellulose-based lubricants such as Pre-Seed ConceivEase do not affect a sperm cell, and the ASRM recommends them to couples wanting to get pregnant, if a lubricant is needed.^xlix

Diet

Research is limited on whether diet improves fertility in in women. Studies show a variety of diets—vegetarian to low-fat to ketogenic to Mediterranean—have mixed results.^l  Data does suggest that consuming foods that contain heavy metals, such as mercury found in heavy seafood diets, may be associated with infertility in both men and women.^li

From a supplement standpoint, women trying to conceive can be proactive in taking a folic acid supplement of at least 400mcg daily. This reduces the chance of neural tube defects such as spina bifida. Folic acid supplementation may also improve the ability to conceive, and it is a general recommendation from every major medical organization worldwide.^lii,liiiFolic acid is often consumed by taking a prenatal multi-vitamin (it includes the folic acid as well as other vitamins). Other supplements, such as vitamin D and Coenzyme Q10 are also recommended by many medical professionals.

Even though no one specific diet has been shown to definitively improve fertility, research shows that eating a healthy, balanced diet that follows general recommendations set out by the United States Dietary Guidelines for Americans improves fertility in women and semen quality in men. Such a diet includes maximizing the consumption of whole grains, monounsaturated and polyunsaturated oils, vegetables, fruits, and fish.^{liv,lv,lvi,lvii}

Drinking alcohol

Regarding fertility and alcohol, research has not conclusively shown that light or moderate alcohol consumption affects female fertility. Large studies show positive, negative, and neutral effects of social alcohol consumption on the ability to conceive.^lviii,lix,lx It is not clear whether heavy alcohol consumption and binge drinking affect ovarian reserve, nor just how much alcohol consumption would be required to impact fertility.^lxi,lxii Some data suggests that, for women, drinking more than four drinks per week while trying to conceive slightly increases miscarriage risk.^{lxiii,lxiv,lxv,lxvi,lxvii}

Some babies born to women who consume alcohol in pregnancy develop fetal alcohol syndrome, though it is unclear why some babies exposed to alcohol in utero develop this condition and others do not. Alcohol is a known teratogen, a substance that can lead to miscarriage or congenital malformations (birth defects) in the fetus.  These occur in the stages of development after implantation.

In men, heavy alcohol use may also affect fertility and semen parameters. It can reduce testosterone, thereby negatively affecting sperm count and quality, both of which are problems that can potentially prevent conception.^lxviii,lxix Additionally, heavy alcohol use and/or abuse can cause liver dysfunction, and the resultant hormonal changes may lead to erectile dysfunction, potentially causing functional issues with getting pregnant at home.^lxx Conversely, research has not shown mild to moderate (social) alcohol use affects semen analysis parameters.^lxxi

Smoking

Smoking negatively impacts health as well as fertility and should be avoided by women trying to get pregnant. One 1998 meta-analysis showed that cigarette smoking in women is associated with reduced fertility in both women attempting to get pregnant at home and those using assisted reproduction.^lxxii It is unclear what level of exposure to cigarette smoking (light, moderate, or heavy) is required to reduce fertility.^lxxiii

There is some evidence that cigarette smoking worsens semen parameters in men, though the level of exposure required and the true effect on the ability to conceive is unclear.^lxxiv

Weight and BMI

Maintaining a body mass index (BMI, I.e., the relationship between height and weight) that falls within standard parameters is important for women trying to get pregnant, as it can affect fertility both if it is too low or too high. For example, women with an elevated BMI, particularly those who fall into the category of obesity, frequently take longer to achieve conception and have a lowered chance of conception as well.^{lxxv,lxxvi,lxxvii} For example, even small changes to improve weight can make an impact on cycle regularity and chances of conception.

Obesity and elevated BMI or weight can also affect men; both have been associated with reduced semen analysis parameters and erectile dysfunction. Many of these effects are thought to be related to increased estrogen: testosterone ratio in males who are overweight.^{lxxviii,lxxix,lxxx}

Supplements and vitamins

Supplements and vitamins are frequently part of conversations about health, fertility, and conception. Regarding female fertility, published literature offers no clear consensus about whether any individual vitamin or supplement improves the ability to conceive. While some data suggests supplementation with multivitamins may improve fertility, this has not been consistently shown in various studies.^lxxxi,lxxxii

Folate supplementation is the only specific vitamin or supplement recommendation from any medical society for women who want to conceive.^{lxxxiii,lxxxiv} In fact, a systematic review of 37 studies from 2012 did not find any overall benefit from any of the studied vitamins or supplements.^lxxxv

If a man has no diagnosed abnormality in semen analysis parameters and no deficiency in vitamin levels, vitamin supplements have not been shown to improve fertility.^{lxxxvi,lxxxvii,lxxxviii}  In men with specific vitamin deficiencies such as low carnitine, supplementation with that vitamin or mineral may be beneficial.^lxxxix

CoQ10 is one supplement that research shows may benefit men who wish to conceive. A 2021 systematic review revealed that CoQ10, which is an essential cofactor for energy production in the body and an antioxidant, has a positive effect on semen analysis parameters. The exact CoQ10 dose needed to maximize male semen parameters is unknown.^xc

When to see a doctor for fertility

The ASRM and the American College of Obstetricians and Gynecologists recommends that couples be referred to a fertility specialist for evaluation after:

•   12 months of unprotected intercourse if the female partner is younger than 35 years
•  Six months of unprotected intercourse if the female partner is older than 35 years

Immediate fertility evaluation is appropriate in certain circumstances, including in women over age 40 due to the high risk of infertility in this age group, as well as for women who have had a prior tubal ligation or other type of tubal surgery. Male fertility evaluation with semen analysis and blood work should always be pursued if female fertility work-up is indicated.^xci

Conclusion

Trying to get pregnant at home can take time. Knowing the lifestyle factors that can contribute to improved or decreased fertility health can be helpful in the journey toward a positive pregnancy test. It can also help potential parents know when it is time to seek help from a fertility specialist in getting pregnant and having a baby.