pregnancy (version 0.2.1)

calculate_test_date: Calculate pregnancy test date

Description

Calculates the recommended date for taking a pregnancy test based on a start date and type. The function supports both urine and blood tests, with blood tests typically being viable 2 days earlier than urine tests.

Usage

calculate_test_date(
  start_date,
  start_type = c("LMP", "conception", "transfer_day_3", "transfer_day_5",
    "transfer_day_6"),
  cycle = 28,
  test_type = c("urine", "blood")
)

Value

Returns a Date object invisibly representing the recommended test date. Also prints informative messages showing:

• The recommended date for a urine test

• The recommended date for a blood test

Arguments

start_date

Date or character string representing a date, e.g. "YYYY-MM-DD". The starting reference date. The interpretation of this date depends on the start_type parameter.

start_type

character. One of:

• "LMP": Last Menstrual Period date (default)

• "conception": Date of conception

• "transfer_day_3": Date of day 3 embryo transfer

• "transfer_day_5": Date of day 5 embryo transfer

• "transfer_day_6": Date of day 6 embryo transfer

cycle

numeric. Length of menstrual cycle in days. Only used when start_type = "LMP". Must be between 20 and 44 days. Defaults to 28 days.

test_type

character. One of:

• "urine": Home pregnancy test (default)

• "blood": Blood test at clinic

Details

The test date is calculated as follows:

1. First, the ovulation date is calculated (see calculate_due_date() for details)

2. For urine tests: 14 days are added to the ovulation date

3. For blood tests: 12 days are added to the ovulation date

Blood tests can typically detect pregnancy earlier than urine tests due to their greater sensitivity in detecting hCG hormone levels.

If start_date is a character string, the conversion to a Date is handled by anytime::anydate().

See Also

• calculate_due_date() for calculating the estimated due date

Examples

# Calculate test date from last menstrual period
calculate_test_date("2025-01-31")

# Calculate for blood test from conception date
calculate_test_date(
  start_date = "5023-02-14",
  start_type = "conception",
  test_type = "blood"
)

# Calculate from day 5 embryo transfer
calculate_test_date(
  as.Date("2025-02-19"),
  start_type = "transfer_day_5"
)

# Calculate with non-standard cycle length
calculate_test_date("2025-01-31", cycle = 35)