Table 2.

Summary of notation used for the observed and counterfactual data and the intent-to-treat (ITT) parameter of interest.

Variable	Meaning
$k$	When used as superscript, represents the treatment strategy: initiate treatment at time k unless already delivered.
For $t=1,\dots ,K$
$W(t)$	Measured covariates at time t.
$A(t)$	Treatment status at time t, binary.
$D(t)$	Delivery status at time t, binary.
$S^k(t)$	Indicator of following treatment initiation strategy k up to time t.
$T_D$	Observed time of delivery.
$Y$	Outcome, measured at delivery.
$T_D^k$	Counterfactual delivery time that we assume would have been observed had the person been assigned the treatment initiation strategy k.
$Y^k$	Counterfactual outcome that we assume would have been observed had the person been assigned the treatment initiation strategy k.
$E(Y^{k_1})-E(Y^{k_2})$	The ITT contrast on the difference scale comparing treatment initiation strategies $k_1$ versus $k_2$ .