Package {simPreg}

Title: Simulate Pregnancy Data with Time-Varying Exposure
Version: 0.1.0
Description: Simulates pregnancy data in a time-to-event framework, allowing a time-varying exposure. Default parameters for gestational length and exposure timing are provided but may also be user-specified. Users can further specify hazard ratios for spontaneous and non-spontaneous live birth and late miscarriage/stillbirth following exposure.
License: MIT + file LICENSE
Encoding: UTF-8
Depends: R (≥ 3.5)
LazyData: true
Config/roxygen2/version: 8.1.0
Suggests: knitr, rmarkdown, survival, testthat (≥ 3.0.0)
Config/testthat/edition: 3
VignetteBuilder: knitr
NeedsCompilation: no
Packaged: 2026-09-16 05:47:18 UTC; SINS
Author: Siri N. Skodvin [aut, cre], Miriam Gjerdevik [ctb], Hakon K. Gjessing [ctb]
Maintainer: Siri N. Skodvin <siri.skodvin@gmail.com>
Repository: CRAN
Date/Publication: 2026-09-27 16:10:02 UTC

Default daily hazard of exposure

Description

Approximate daily hazard rates of exposure by gestational day, from day 1 through day 301 of gestation.

Usage

haz.exposure.default

Format

A numeric vector of length 301. Element i corresponds to gestational day i.

Default daily hazard of late miscarriage/stillbirth

Description

Approximate daily hazard rates of late miscarriage/stillbirth by gestational day, from day 1 through day 301 of gestation. Hazard rates are set to 0 for gestational days 1 through 83 because the data used to specify the default hazard do not include early miscarriage. Positive hazard rates begin at gestational day 84.

Usage

haz.late.miscarriage.stillbirth.default

Format

A numeric vector of length 301. Element i corresponds to gestational day i.

Default daily hazard of non-spontaneous live birth

Description

Approximate daily hazard rates of non-spontaneous live birth by gestational day, from day 1 through day 301 of gestation. Hazard rates are set to 0 for gestational days 1 through 153, reflecting that 22 weeks of gestation is approximately the lower gestational-age limit at which active neonatal care is considered in Norwegian clinical practice. Positive hazard rates begin at gestational day 154.

Usage

haz.nonspont.livebirth.default

Format

A numeric vector of length 301. Element i corresponds to gestational day i.

Default daily hazard of spontaneous live birth

Description

Approximate daily hazard rates of spontaneous live birth by gestational day, from day 1 through day 301 of gestation. Hazard rates are set to 0 for gestational days 1 through 153, reflecting that 22 weeks of gestation is approximately the lower gestational-age limit at which active neonatal care is considered in Norwegian clinical practice. Positive hazard rates begin at gestational day 154.

Usage

haz.spont.livebirth.default

Format

A numeric vector of length 301. Element i corresponds to gestational day i.

Simulate distributions of pregnancy outcomes and gestational duration

Description

Calculates proportions of pregnancies experiencing spontaneous live birth, non-spontaneous live birth, or late miscarriage/stillbirth by gestational age and timing of exposure, given daily hazard rates and hazard ratios.

Usage

simPregProp(
  haz.spont.livebirth = haz.spont.livebirth.default,
  haz.nonspont.livebirth = haz.nonspont.livebirth.default,
  haz.late.miscarriage.stillbirth = haz.late.miscarriage.stillbirth.default,
  haz.exposure = haz.exposure.default,
  hr.spont.livebirth = NULL,
  hr.nonspont.livebirth = NULL,
  hr.late.miscarriage.stillbirth = NULL
)

Arguments

haz.spont.livebirth

Numeric vector of daily hazards of spontaneous live birth. Defaults to the package-provided haz.spont.livebirth.default vector of length 301.

haz.nonspont.livebirth

Numeric vector of daily hazards of non-spontaneous live birth. Defaults to the package-provided haz.nonspont.livebirth.default vector of length 301.

haz.late.miscarriage.stillbirth

Numeric vector of daily hazards of late miscarriage/stillbirth. Defaults to the package-provided haz.late.miscarriage.stillbirth.default vector of length 301.

haz.exposure

Numeric vector of daily hazards of exposure. Defaults to the package-provided haz.exposure.default vector of length 301.

hr.spont.livebirth

Numeric vector of hazard ratios for spontaneous live birth following exposure. Must have the same length as the hazard vectors. Defaults to NULL, corresponding to no effect of exposure on the hazard.

hr.nonspont.livebirth

Numeric vector of hazard ratios for non-spontaneous live birth following exposure. Must have the same length as the hazard vectors. Defaults to NULL, corresponding to no effect of exposure on the hazard.

hr.late.miscarriage.stillbirth

Numeric vector of hazard ratios for late miscarriage/stillbirth following exposure. Must have the same length as the hazard vectors. Defaults to NULL, corresponding to no effect of exposure on the hazard.

Value

A data frame with class preg.prop containing the following columns:

GA

Gestational age in days.

ExpGA

Gestational age at exposure. NA indicates no exposure.

Outcome

Pregnancy outcome: spontaneous_live_birth, nonspontaneous_live_birth, or late_miscarriage_stillbirth.

Prop

Proportion of pregnancies corresponding to the gestational age, exposure timing, and outcome combination.

Examples

# Use the package-provided default hazard vectors
data.prop <- simPregProp()
head(data.prop)

# Illustrate an exposure associated with increased risk of preterm live birth
hr <- rep(1, 301)
hr[1:258] <- 2
data.prop <- simPregProp(
  hr.spont.livebirth = hr,
  hr.nonspont.livebirth = hr
)

Sample pregnancies from simulated distributions

Description

Generates a sample of pregnancy outcomes from the proportions produced by simPregProp().

Usage

simPregSamp(df, n, expand = FALSE)

Arguments

df

A data frame with class preg.prop, such as the output from simPregProp().

n

Number of pregnancies to sample. Must be a positive integer.

expand

Logical value indicating whether to expand the sampled counts into one row per pregnancy. Defaults to FALSE.

Value

A data frame with class data.frame containing the sampled pregnancy outcomes and their frequencies. The returned data frame retains the columns of df and includes an additional Freq column containing the number of sampled pregnancies for each gestational age, exposure timing, and outcome combination.

If expand = TRUE, rows are expanded so that each row represents one pregnancy, and Freq is set to 1.

Examples

# Generate pregnancy outcome proportions
data.prop <- simPregProp()

# Sample 1000 pregnancies
data.samp <- simPregSamp(data.prop, 1000)
head(data.samp)

# Expand to one row per pregnancy
data.samp <- simPregSamp(data.prop, 1000, expand = TRUE)
head(data.samp)