Researchers in The Cochrane Collaboration reviewed the evidence about the effect of timed intercourse versus spontaneous intercourse in couples trying to conceive.
Many couples find it difficult to achieve a pregnancy and have concerns about their fertility. Each cycle, a woman is fertile from approximately five days before ovulation until several hours after ovulation, due to limited survival times of the sperm and egg. Therefore, prospectively identifying this fertile period of a woman's menstrual cycle, to guide timing of intercourse, may improve conception rates. This may reduce unnecessary medical treatment and costs of advanced infertility treatment, but could also cause adverse events such as stress. The fertile period can be identified by different methods including urinary fertility monitoring, calendar charting, observing changes in cervical mucous and basal body temperatures or follicular maturation on ultrasound. The aim of this review was to assess the benefits and risks of timed intercourse on pregnancy outcomes in couples trying to conceive.
We found five randomised controlled trials comparing timed intercourse versus intercourse without ovulation prediction, in a total of 2840 women or couples trying to conceive. The evidence was current to August 2014.
One large included study (1453 women) has not published usable results and could therefore not be analysed. One study reported live birth rates and found no evidence of a difference; however, the study was too small to have any clinical value. Only one study reported levels of stress and showed no evidence of a difference between timed intercourse with urinary fertility monitoring and intercourse without urinary fertility monitoring. No other adverse events were reported. Only two studies reported clinical pregnancy rates, and showed no evidence of a difference in pregnancy rates in couples with subfertility. The evidence suggested that if the chance of a clinical pregnancy following intercourse without ovulation prediction was assumed to be 16%, the chance of a clinical pregnancy following timed intercourse would be between 9% and 33%. However, if including self-reported pregnancies (not confirmed by ultrasound), pregnancy rates were higher after timed intercourse. The evidence suggested that if the chance of a pregnancy following intercourse without ovulation prediction was 13%, the chance following timed intercourse would be between 14% and 23%.
No difference in effect was found between couples trying to conceive for less than 12 months versus 12 months or more. One trial reported time to conception data and showed no evidence of a difference in time to conception.
Quality of the evidence
The overall quality of the evidence ranged from low to very low for all outcomes. The main limitations of the evidence were imprecision, poor reporting of clinically relevant outcomes and a high risk of publication bias, as one large study remains unpublished. Therefore, the findings should be regarded with caution.
There are insufficient data available to draw conclusions on the effectiveness of timed intercourse for the outcomes of live birth, adverse events and clinical pregnancy. Timed intercourse may improve pregnancy rates (clinical or self-reported pregnancy, not yet confirmed by ultrasound) compared to intercourse without ovulation prediction. The quality of this evidence is low to very low and therefore findings should be regarded with caution. There is a high risk of publication bias, as one large study remains unpublished 8 years after recruitment finished. Further research is required, reporting clinically relevant outcomes (live birth, clinical pregnancy rates and adverse effects), to determine if timed intercourse is safe and effective in couples trying to conceive.
Fertility problems are very common, as subfertility affects about 10% to 15% of couples trying to conceive. There are many factors that may impact a couple's ability to conceive and one of these may be incorrect timing of intercourse. Conception is only possible from approximately five days before up to several hours after ovulation. Therefore, to be effective, intercourse must take place during this fertile period. 'Timed intercourse' is the practice of prospectively identifying ovulation and, thus, the fertile period to increase the likelihood of conception. Whilst timed intercourse may increase conception rates and reduce unnecessary intervention and costs, there may be associated adverse aspects including time consumption and stress. Ovulation prediction methods used for timing intercourse include urinary hormone measurement (luteinizing hormone (LH), estrogen), tracking basal body temperatures, cervical mucus investigation, calendar charting and ultrasonography. This review considered the evidence from randomised controlled trials for the use of timed intercourse on positive pregnancy outcomes.
To assess the benefits and risks of ovulation prediction methods for timing intercourse on conception in couples trying to conceive.
We searched the following sources to identify relevant randomised controlled trials, the Menstrual Disorders and Subfertility Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, PsycINFO, PubMed, LILACS, Web of Knowledge, the World Health Organization (WHO) Clinical Trials Register Platform and ClinicalTrials.gov. Furthermore, we manually searched the references of relevant articles. The search was not restricted by language or publication status. The last search was on 5 August 2014.
We included randomised controlled trials (RCTs) comparing timed intercourse versus intercourse without ovulation prediction or comparing different methods of ovulation prediction for timing intercourse against each other in couples trying to conceive.
Two review authors independently assessed trial eligibility and risk of bias and extracted the data. The primary review outcomes were cumulative live birth and adverse events (such as quality of life, depression and stress). Secondary outcomes were clinical pregnancy, pregnancy (clinical or self-reported pregnancy, not yet confirmed by ultrasound) and time to conception. We combined data to calculate pooled risk ratios (RRs) and 95% confidence intervals (CIs). Statistical heterogeneity was assessed using the I2 statistic. We assessed the overall quality of the evidence for the main comparisons using GRADE methods.
We included five RCTs (2840 women or couples) comparing timed intercourse versus intercourse without ovulation prediction. Unfortunately one large study (n = 1453) reporting live birth and pregnancy had not published outcome data by randomised group and therefore could not be analysed. Consequently, four RCTs (n = 1387) were included in the meta-analysis. The evidence was of low to very low quality. Main limitations for downgrading the evidence included imprecision, lack of reporting clinically relevant outcomes and the high risk of publication bias.
One study reported live birth, but the sample size was too small to draw any relevant conclusions on the effect of timed intercourse (RR 0.75, 95% CI 0.16 to 3.41, 1 RCT, n = 17, very low quality).
One study reported stress as an adverse event. There was no evidence of a difference in levels of stress (mean difference 1.98, 95 CI% -0.87 to 4.83, 1 RCT, n = 77, low level evidence). No other studies reported adverse events.
Two studies reported clinical pregnancy. There was no evidence of a difference in clinical pregnancy rates (RR 1.10, 95% CI 0.57 to 2.12, 2 RCTs, n = 177, I2 = 0%, low level evidence). This suggested that if the chance of a clinical pregnancy following intercourse without ovulation prediction is assumed to be 16%, the chance of success following timed intercourse would be between 9% and 33%.Four studies reported pregnancy rate (clinical or self-reported pregnancy). Timed intercourse was associated with higher pregnancy rates compared to intercourse without ovulation prediction in couples trying to conceive (RR 1.35, 95% CI 1.06 to 1.71, 4 RCTs, n = 1387, I2 = 0%, very low level evidence). This suggests that if the chance of a pregnancy following intercourse without ovulation prediction is assumed to be 13%, the chance following timed intercourse would be between 14% and 23%. Subgroup analysis by duration of subfertility showed no difference in effect between couples trying to conceive for < 12 months versus couples trying for ≥ 12 months. One trial reported time to conception data and showed no evidence of a difference in time to conception.