Pregnancy/Data

Mother's Age

Age Group	Pregnancy Chance per Cycle	Relative Odds vs. 25-29
20-24	0.25	1.0
25-29	0.20	1.0
30-34	0.15	0.85
35-39	0.10	0.70
40-44	0.05	0.50

The fecundity rates per cycle and odds ratios are averages derived from multiple studies on age-related fertility decline, where base rates were normalized (e.g., averaging reported probabilities like 20-25% for ages 20-24 across sources) and odds ratios calculated relative to the peak fertility group.

• Dunson, D. B., et al. (2002). Changes with age in the level and duration of fertility in the menstrual cycle. Human Reproduction.
• American College of Obstetricians and Gynecologists. (2014). Female age-related fertility decline. Fertility and Sterility.

Father's Age

Age Group	Fecundity Reduction per Cycle	Relative Odds vs. 25-34
20-29	0.00	1.0
30-34	0.05	0.95
35-39	0.10	0.85
40-44	0.20	0.70
45+	0.30	0.60

The fecundity reductions and odds ratios are based on aggregated data from studies, with reductions estimated as proportional decreases (e.g., averaging 5-10% for 35-39 from reported time-to-pregnancy increases) and odds ratios inverted from relative risks for subfertility.

• Khandwala, Y. S., et al. (2020). The age of fathers in the USA and the risk of adverse pregnancy outcomes. Reproductive Biology and Endocrinology.
• du Fossé, N. A., et al. (2023). The impact of paternal age on perinatal outcomes: A systematic review. Human Reproduction Update.

Contraception Methods

Method	Typical Use Failure Rate	Perfect Use Failure Rate
No method	0.85	0.85
Implant	0.0005	0.0005
IUD	0.008	0.002
Injectable	0.04	0.003
Pill	0.07	0.003
Patch	0.07	0.003
Ring	0.07	0.003
Male condom	0.13	0.02
Female condom	0.21	0.05
Diaphragm	0.17	0.06
Spermicide	0.21	0.18
Withdrawal	0.20	0.04

No calculations were performed; data is directly from standardized CDC effectiveness rates.

• Centers for Disease Control and Prevention. (2023). Contraceptive Effectiveness in the United States.

Menstrual Cycle Day

Day Relative to Ovulation	Conception Probability
-5	0.05
-4	0.13
-3	0.27
-2	0.30
-1	0.30
0	0.30
+1	0.00

No calculations were performed; probabilities are direct averages from the landmark study on conception timing.

• Wilcox, A. J., et al. (1995). Timing of sexual intercourse in relation to ovulation: Effects on the probability of conception. New England Journal of Medicine.

Intercourse Frequency

Frequency per Week	Pregnancy Chance per Cycle	Relative Odds vs. <1 Time
<1	0.10	1.0
1-2	0.15	1.50
3-4	0.20	2.00
Daily	0.25	2.50

Fecundity rates and odds ratios are approximated by averaging reported increases in pregnancy rates from studies (e.g., scaling base 10% for infrequent to 25% for daily based on fertile window coverage).

• Stanford, J. B., et al. (2020). Optimizing natural fertility: A committee opinion. Fertility and Sterility.
• American Society for Reproductive Medicine. (2021). Optimizing natural fertility.

BMI Categories

BMI Range	Fecundity Reduction per Cycle	Relative Odds vs. 18.5-24.9
<18.5 (underweight)	0.20	1.50
18.5-24.9 (normal)	0.00	1.0
25-29.9 (overweight)	0.10	1.20
30-34.9 (obese class I)	0.20	1.50
35-39.9 (obese class II)	0.30	1.80
>=40 (obese class III)	0.40	2.00

Reductions and odds ratios are averaged from meta-analyses, converting reported relative risks for infertility (e.g., 1.2-2.0 for obesity) into proportional fecundity drops.

• Silvestris, E., et al. (2022). Obesity and female fertility: A comprehensive review. Reproductive Biology and Endocrinology.
• Best, D., et al. (2023). The impact of body mass index on female fertility. Human Reproduction.

Smoking Status

Status	Cigarettes per Day	Fecundity Reduction per Cycle	Relative Odds for Infertility
Nonsmoker	0	0.00	1.0
Light smoker	1-10	0.10	1.30
Moderate smoker	11-20	0.20	1.60
Heavy smoker	>20	0.30	2.00

Reductions are estimated by averaging dose-response data from reviews, translating odds ratios into percentage fecundity decreases (e.g., OR 1.3 implies ~10% reduction).

• Augood, C., et al. (1998). Smoking and female infertility: A systematic review and meta-analysis. Human Reproduction.

Alcohol Consumption

Drinks per Week	Fecundity Reduction per Cycle	Relative Odds vs. Nondrinker
None	0.00	1.0
1-5 (light)	0.05	1.10
6-10 (moderate)	0.15	1.30
>10 (heavy)	0.25	1.60

Reductions are averaged from dose-response meta-analyses, converting odds ratios for reduced fecundability into proportional decreases (e.g., OR 1.3 ≈ 15% reduction).

• Fan, D., et al. (2017). Female alcohol consumption and fecundability: A systematic review and dose-response meta-analysis. Scientific Reports.
• Eggert, J., et al. (2004). Effects of alcohol consumption on female fertility during an 18-month period. Fertility and Sterility.

  RiskModel: Pregnancy/Data:chance_of_getting_pregnant_in_a_month
Calculation: (fecundity_per_cycle * odds_ratio_vs_25_29 * odds_ratio_vs_25_34 * (1 / odds_ratio_vs_18_5_24_9) * (1 / odds_ratio_for_infertility) * (1 / (odds_ratio_vs_nondrinker)) * odds_ratio_vs_1_time * (typical_use_failure_rate / 0.85)) * 100
    Content: The estimated chance of getting pregnant in a month (per menstrual cycle) is about {result}%.

  RiskModel: Pregnancy/Data:chance_of_getting_pregnant_from_one_act_of_intercourse
Calculation: (conception_probability * odds_ratio_vs_25_29 * odds_ratio_vs_25_34 * (1 / (odds_ratio_vs_18_5_24_9)) * (1 / (odds_ratio_for_infertility)) * (1 / (odds_ratio_vs_nondrinker)) * (typical_use_failure_rate / 0.85)) * 100
    Content: The estimated chance of getting pregnant from one act of intercourse is about {result}%.