View source for Chances of Getting Pregnant After Sex/Data

'''Per-day conception probabilities (verbatim)'''

<datatable2 table="conception_probability_by_cycle_day" columns="day_relative_to_ovulation|per_act_probability_day_specific">
<head>
!Days before or on ovulation (day 0)
!Probability of conception per act (verbatim)
</head>
5|0.10
4|0.17
3|0.24
2|0.30
1|0.33
0|0.33
</datatable2>

Copied verbatim from:

* Wilcox AJ, Weinberg CR, Baird DD. "Timing of sexual intercourse in relation to ovulation: Effects on the probability of conception, survival of the pregnancy, and sex of the baby." ''New England Journal of Medicine''. 1995;333(23):1517–1521. [https://www.nejm.org/doi/full/10.1056/NEJM199512073332301 Link]


'''Friendly timing options (verbatim-based selections)'''

<datatable2 table="friendly_timing_options" columns="timing_label|per_act_probability_friendly">
<head>
!When did sex happen?
!Chance of getting pregnant (per act)
</head>
Not sure (timing unknown)|0.031
A few days before ovulation (1–2 days before)|0.30
Day of ovulation|0.33
Earlier in the fertile window (3–5 days before)|0.24
</datatable2>

Notes and references:  
* **“Not sure (timing unknown) = 0.031 per act**:** Wilcox AJ et al. (2001) estimated the probability of pregnancy from a single **random** act of unprotected intercourse at **3.1%**. This serves as a population-average when timing is unknown. * Wilcox AJ, Dunson D, Weinberg CR, Trussell J, Baird DD. "Likelihood of conception with a single act of intercourse: providing benchmark rates for assessment of post-coital contraceptives." ''Contraception''. 2001;63(4):211–215. [https://pubmed.ncbi.nlm.nih.gov/11376648/ PubMed]
  
* **“A few days before ovulation (1–2 days before) = 0.30”** and **“Day of ovulation = 0.33”** are **verbatim** from Wilcox 1995 for days −2 and 0. :contentReference[oaicite:2]{index=2}  
* **“Earlier in the fertile window (3–5 days before) = 0.24”** uses the **verbatim** day −3 figure (0.24) from Wilcox 1995 as a representative value for earlier fertile-window timing (days −3 to −5 are 0.24, 0.17, 0.10 respectively). We select 0.24 to avoid under- or over-stating risk while keeping numbers copied from the source. Reviewers can see all day-specific values above.

<RiskModel name="conception_model" calculation="per_act_probability_friendly / 1">
The chance of getting pregnant is {{One_In_X|{result}}}.
</RiskModel>

''Calculation note'': The friendly options reference **verbatim** probabilities from the cited studies (either a specific day from Wilcox 1995 or the “random-timing” average of **0.031** from Wilcox 2001). No averaging is performed inside the tables; the RiskModel simply uses the selected per-act probability as-is.

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