README.md
In pregnancy: Calculate and Track Dates and Medications During Pregnancy

pregnancy

This is an R package for calculating dates and tracking medications during pregnancy and fertility treatment. It extends a private, personal package that I wrote for myself when I was pregnant. It contains functions and features that I found useful at the time, and others that I added when adapting the package for general use.

The functionality goes beyond what’s offered by online pregnancy calculators and apps, plus there are no concerns (unlike with these sites and apps) about data privacy, tracking or advertising.

pregnancy is available on CRAN:

install.packages("pregnancy")

You can install the development version from or R-universe:

install.packages("pregnancy", repos = "https://ellakaye.r-universe.dev")

Alternatively, install the development version from GitHub with:

pak::pak("EllaKaye/pregnancy")

This is a quick tour. For a more extensive guide, see the Get Started vignette, vignette("pregnancy").

library(pregnancy)

# invisibly returns a Date object with the estimated due date
# by default, start date of last menstrual period, but other options available
due_date <- calculate_due_date("2025-02-24")
#> ℹ Estimated due date: Monday, December 01, 2025
#> ℹ Estimated birth period begins: November 10, 2025 (37 weeks)
#> ℹ Estimated birth period ends: December 15, 2025 (42 weeks)

# set the pregnancy.due_date option
# avoids having to pass the due date as argument to other functions
set_due_date(due_date)
#> ✔ Due date set as December 01, 2025
#> ℹ Functions in the pregnancy package will now use this `due_date` option.
#> ℹ So, for this R session, you do not need to supply a value to the `due_date`
#>   argument (unless you wish to override the option).
#> ℹ To make this `due_date` option available in all R sessions, in your
#>   ".Rprofile", set `options(pregnancy.due_date = ...)`
#>   where ... is the value of `due_date`.
#> ℹ You can edit your ".Rprofile" by calling `usethis::edit_r_profile()`
#> ℹ You can retrieve the `due_date` option with `get_due_date()`,
#>   or with `getOption('pregnancy.due_date')`.

This README was built on September 04, 2025, so for the purposes of reading this page, that counts as “today”.

# don't need to specify `due_date` since option is set
# invisibly returns number of days into the pregnancy
how_far()
#> ℹ You are 27 weeks and 3 days pregnant.
#> ℹ That's 12 weeks and 4 days until the due date (December 01, 2025).
#> ℹ You are 69% through the pregnancy.

# alternative `on_date`, addressed as "I"
how_far(on_date = "2025-09-17", person = 1)
#> ℹ On September 17, 2025, I will be 29 weeks and 2 days pregnant.

# when a given week of the pregnancy is reached
# invisibly returns the Date when that week is reached
date_when(33)
#> ℹ On October 13, 2025, you will be 33 weeks pregnant.
#> ℹ That's 5 weeks and 4 days away.

# a simplified medication schedule
meds <- dplyr::tribble(
  ~medication, ~format, ~quantity, ~start_date, ~stop_date,
  "progynova", "tablet", 3, "2025-08-21", "2025-08-31",
  "progynova", "tablet", 6, "2025-09-01", "2025-09-11",
  "cyclogest", "pessary", 2, "2025-09-03", "2025-09-11",
  "clexane", "injection", 1, "2025-09-08", "2025-11-05"
)

# how much of each medication is left to take, as of "today"
medications_remaining(meds)
#> # A tibble: 3 × 2
#>   medication quantity
#>   <chr>         <int>
#> 1 clexane          59
#> 2 cyclogest        16
#> 3 progynova        48

# how much medication for a given week 
# (useful if you need to request a prescription to cover a certain time period)
medications_remaining(meds, on_date = "2025-09-01", until_date = "2025-09-07")
#> # A tibble: 2 × 2
#>   medication quantity
#>   <chr>         <int>
#> 1 cyclogest        10
#> 2 progynova        42

how_far() and date_when() both need to know the pregnancy due date, and this can be passed directly to the due_date argument. It would be very tedious, however, to have to enter a due date every time you call these functions over the course of a pregnancy, especially since that date is constant throughout. The same holds for the for medications table required for medications_remaining().

To avoid this, the pregnancy package makes use of global options, which can be set with the set_* family of functions (set_due_date(), set_person(), set_medications()), and retrieved with the corresponding get_* family of functions (get_due_date(), get_person(), get_medications()). These options will persist for the duration of the current R session.

Any global option can be unset by calling its set_* function with the argument NULL.

# a different due date from the earlier example
set_due_date("2026-04-01")
#> ✔ Due date set as April 01, 2026
#> ℹ Functions in the pregnancy package will now use this `due_date` option.
#> ℹ So, for this R session, you do not need to supply a value to the `due_date`
#>   argument (unless you wish to override the option).
#> ℹ To make this `due_date` option available in all R sessions, in your
#>   ".Rprofile", set `options(pregnancy.due_date = ...)`
#>   where ... is the value of `due_date`.
#> ℹ You can edit your ".Rprofile" by calling `usethis::edit_r_profile()`
#> ℹ You can retrieve the `due_date` option with `get_due_date()`,
#>   or with `getOption('pregnancy.due_date')`.

how_far()
#> ℹ You are 10 weeks and 1 day pregnant.
#> ℹ That's 29 weeks and 6 days until the due date (April 01, 2026).
#> ℹ You are 25% through the pregnancy.

# check and then unset option
get_due_date()
#> ℹ Your due date is set as April 01, 2026.
set_due_date(NULL)
#> ✔ pregnancy.due_date option set to NULL.
#> ℹ You will need to explicitly pass a value to the `due_date` argument
#>   in functions that use it, or reset the option with `set_due_date()`.

Options in `.Rprofile`

We recommend adding your options to your .Rprofile so they persist across R sessions. R will read in these options at the start of each session, and you will not need to use the set_* family of functions, nor pass them as arguments to the package functions. The get_* family of functions will still retrieve the options set in .Rprofile.

Here’s an example of what that might look like:

options(
  pregnancy.due_date = "2025-09-16",
  pregnancy.person = "I", # addressed in first person
  pregnancy.medications = tibble::tribble(
  ~medication, ~format, ~quantity, ~start_date, ~stop_date,
  "progynova", "tablet", 3, "2025-08-21", "2025-08-31",
  "progynova", "tablet", 6, "2025-09-01", "2025-09-11",
  "cyclogest", "pessary", 2, "2025-09-03", "2025-09-11",
  "clexane", "injection", 1, "2025-09-08", "2025-11-05"
  ) 
)

Note that it is best to avoid creating R objects in your .Rprofile, e.g. a medications data frame outside of the call to options(), otherwise that object will be loaded into your global environment at the start of every R session.

See package website at https://ellakaye.github.io/pregnancy/ and also in the installed package: help(package = "pregnancy").