Pregnancy Testing Outcomes Predictor for Clinical Trials

This interactive tool helps investigators, sponsors, regulators, and others in designing a pregnancy testing plan for a clinical trial by estimating the likelihood of a woman enrolling in the study while pregnant, or becoming pregnant during the study.

By calculating the probability of pregnant participants, the tool provides a quantitative method to assess the advantages (reduced risk of embryo/fetal exposure) versus burdens (participant burden, study team workload, costs, etc.) of a pregnancy testing plan, as recommended by the CTTI Pregnancy Testing Project. Users can change the values of certain key variables to compare the probability of pregnant participants under different assumptions. Click here for more information on the outcomes predictor's calculations.

Note: The tool does NOT provide explicit guidance on the optimal pregnancy testing plan for a clinical trial. The level of acceptable risk of unintended embryo/fetal exposure to a trial intervention is based on judgment by investigators, sponsors, and regulators. The tool provides estimates of risk for each pregnancy testing plan, and it is up to users to determine which plan is acceptable.


18 - 19 years% 20 - 24 years% 25 - 29 years%
30 - 34 years% 35 - 39 years% 40 - 44 years%
45 - 49 years% 50 - 54 years% ≥ 55 years%
Calculate
Based on Your Study Characteristics
Total number of females of reproductive potential ???
Total undiagnosed pregnancies within 1 month prior to screening
With no use of contraception ???
With "population" distribution of contraceptive methods info ???
With highly effective methods only info ???
Total pregnancies during the study
With no use of contraception ???
With "population" distribution of contraceptive methods info ???
With highly effective methods only ???

Note: The model does not adjust for the high rate of early spontaneous pregnancy loss. A substantial proportion of pregnancies detected by testing would end in early miscarriage 1 , meaning fewer pregnancies would actually be at risk for exposure to study interventions.

Assuming Randomly Timed Testing and Population Distribution of Contraception
Detected Pregnancy info "Undetected" pregnancy False positive / indeterminate info True negative
hCG below threshold info Test performed prior to implantation info
Initial Screening (???) info
Serum ??? ??? ??? ??? ???
Urine, threshold 20 mIU ??? ??? ??? ??? ???
Urine, threshold 25 mIU ??? ??? ??? ??? ???
Urine, threshold 50 mIU ??? ??? ??? ??? ???
Monthly Testing During ??? Months of Study (???) info
Serum ??? ??? ??? ??? ???
Urine, threshold 20 mIU ??? ??? ??? ??? ???
Urine, threshold 25 mIU ??? ??? ??? ??? ???
Urine, threshold 50 mIU ??? ??? ??? ??? ???
Assuming Randomly Timed Testing and Highly Effective Methods Only
Detected pregnancy "Undetected" pregnancy False positive / indeterminate True negative
hCG below threshold Test performed prior to implantation
Initial Screening (???) info
Serum ??? ??? ??? ??? ???
Urine, threshold 20 mIU ??? ??? ??? ??? ???
Urine, threshold 25 mIU ??? ??? ??? ??? ???
Urine, threshold 50 mIU ??? ??? ??? ??? ???
Monthly Testing During ??? Months of Study (???) info
Serum ??? ??? ??? ??? ???
Urine, threshold 20 mIU ??? ??? ??? ??? ???
Urine, threshold 25 mIU ??? ??? ??? ??? ???
Urine, threshold 50 mIU ??? ??? ??? ??? ???
How the tool works:

User Input: The tool requires users to estimate three characteristics of the proposed study:

  • The total number of women expected to be enrolled.
  • The duration of the time during which participants should avoid pregnancy (in months). This should include any pre-intervention assessment/wash-out, time during which participants are receiving trial-related interventions, and any post-exposure time during which pregnancy is to be avoided based on preclinical or other data.
  • The expected age distribution of female participants. Because age is the single biggest predictor of pregnancy risk, and because pregnancy probabilities change dramatically after age 35, the tool asks for estimates in 5-year age increments from age 18 through 54, then for the remaining percentage over age 55.

Model/Tool Outputs:

Based on the number of women at risk for pregnancy, their age distribution, and the study duration, the model estimates the number of expected test results for different thresholds of hCG detectability. Note that some numbers may be less than 1.0 for relatively small studies with few women at risk.

Detected pregnancies: Women with pregnancies and hCG levels above the threshold of a given hCG test.

Undetected pregnancies, hCG below threshold: Women with pregnancies and hCG levels below the threshold of a given hCG test.

Undetected pregnancies, test performed prior to implantation: Women who will become pregnant in a given month but whose randomly timed pregnancy test is performed in the 3 weeks prior to implantation.

False positive/indeterminate: Non-pregnant women (typically perimenopausal women) with very low levels of pituitary hCG.