Protocol - Difficulty Getting Pregnant - Current Duration

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Depending on the aims of the project and feasibility, there are three widely used methods to assess difficulty getting pregnant or impaired fecundity. These include retrospective assessment, prospective assessment, and the current duration approach.

For the retrospective approach (also the approach used for cross-sectional studies), women or couples are asked if the pregnancy was planned and, if yes, how many months it took to get pregnant. It is important to note that this approach can only be used with women or couples who planned their pregnancies.

For prospective assessment, women or couples are followed over time as they try to get pregnant. Women or couples are asked to record exposure data, menstrual cycle data, intercourse, and pregnancy status prospectively over time. Again, this method can only be employed with women or couples who are planning a pregnancy.

If investigators are interested in exposures among women or couples who are not planning a pregnancy, the current duration approach can be used. For this approach, women or couples are asked about the date that they last used contraception.

Specific Instructions:

The PhenX Expert Review Panel recommends this question be asked of either men or women, ages 15 and older.


1) When did you last use contraception?


Mo Yr

2) Calculate the number of months of unprotected intercourse from the time contraception last used til the date of the interview.

Round up number of months. ___________ months

Protocol Name from Source:

N/A, see source.


Publicly available

Personnel and Training Required


Equipment Needs

If a computer-assisted instrument is used, computer software may be necessary to develop the instrument. The interviewer will require a laptop computer/handheld computer to administer a computer-assisted questionnaire.

Requirement CategoryRequired
Major equipment No
Specialized training No
Specialized requirements for biospecimen collection No
Average time of greater than 15 minutes in an unaffected individual No
Mode of Administration

Interviewer-administered questionnaire

Life Stage:

Adolescent, Adult


Women aged 25 to 44

Selection Rationale

These approaches were chosen to reflect the most modern widely accepted methods of measuring time to pregnancy.



Common Data Elements (CDE) Person Current Duration Conception Difficulty Assessment Description Text 3007441 CDE Browser
Derived Variables


Process and Review

The Expert Review Panel #5 (ERP 5) reviewed the measures in the Reproductive Health domain.

Guidance from ERP 5 includes the following:

· Changed the name of the measure

· Replaced protocol

· New Data Dictionary

Back-compatible: there are changes to the Data Dictionary, previous version of the Data Dictionary and Variable mapping in Toolkit archive (link)


Slama, R., Ducot, B., Carstensen, L., Lorente, C., De La Rochebrochard, E., Leridon, H., Keiding, N., Bouyer, J. (2006). Feasibility of the Current-Duration Approach to Studying Human Fecundity. Epidemiology, 17(4), 440-449.

General References

Buck Louis, G. M., Schisterman, E. F., Sweeney, A. M., Wilcosky, T. C., Gore-Langton, R. E., Lynch, C. D., Boyd Barr, D., Schrader, S. M., Kim, S., Chen, Z., & Sundaram, R.; LIFE Study. (2011). Designing prospective cohort studies for assessing reproductive and developmental toxicity during sensitive windows of human reproduction and development-The LIFE Study. Paediatric and Perinatal Epidemiology, 25(5), 413-424.

Keiding, N., Kvist, K., Hartvig, H., Tvede, M., & Juul, S. (2002). Estimating time to pregnancy from current durations in a cross‐sectional sample. Biostatistics, 3(4), 565-578.

Nguyen, R. H., Baird, D. D. (2005). Accuracy of men’s recall of their partner’s time to pregnancy. Epidemiology, 16(5), 694-698.

Slama, R., Ducot, B., Carstensen, L., Lorente, C., De La Rochebrochard, E., Leridon, H., Keiding, N., Bouyer, J. (2006). Feasibility of the Current-Duration Approach to Studying Human Fecundity. Epidemiology, 17(4), 440-449.

Tingen, C., Stanford, J. B., Dunson, D. B. (2004). Methodologic and statistical approaches to studying human fertility and environmental exposure. Environmental Health Perspectives, 112(1), 87-93.

Weinberg, C. R., Baird, D. D., Wilcox, A. J. (1994). Sources of bias in studies of time to pregnancy. Statistics in Medicine, 13(5-7), 671-681.

Protocol ID:


Export Variables
Variable NameVariable IDVariable DescriptionVersiondbGaP Mapping
Reproductive Health
Measure Name:

Difficulty Getting Pregnant

Release Date:

April 11, 2017


Methods to assess the length of time that male and female partners have been trying to get pregnant.


These methods ascertain whether a person and his or her partner are trying to become pregnant and how long they have been trying. Difficulty in conceiving may have genetic or epigenetic origins and is also related to lifestyle and environmental exposures.


Reproductive health, infertility, pregnancy, Pregnancy Study Online, PRESTO, subfertility, impaired fecundity