Calculating pregnancy weeks after a miscarriage can be difficult. Generally, the gestational age at the time of a miscarriage is used to calculate how many weeks pregnant you were when it happened. To do this, your healthcare provider will subtract the number of weeks since your last menstrual period (LMP) from the number of weeks that have passed since your miscarriage occurred. For example, if you had an 8-week old fetus at the time of your miscarriage, and four weeks have passed since then, you would calculate that you were 4 weeks pregnant at the time of your loss. It is important to recognize that due to variations in fetal growth rates and miscalculation by sonographers or clinicians while calculating gestational age before a pregnancy loss occurs; there may be some discrepancy between what was initially estimated and what actually occurred during labor or delivery. Some women also choose not to use their LMP as their starting point for calculating post-miscarriage pregnancies because they want a fresh start with each new pregnancy cycle; however this should only be done with consultation from your healthcare provider as it could potentially lead to inaccurate calculations about gestational age in future pregnancies.