Background
The cytotoxic management of ectopic pregnancy using a single dose of intramuscular methotrexate injection has been well established as effective for a select number of women with unruptured tubal ectopic pregnancy where there are minimal symptoms.

Aim
The purpose of this study was to create centile curves of serum β‐hCG levels following successful treatment with a single dose of 50 mg/m2 of intramuscular methotrexate to treat ectopic pregnancy.

Material and Methods
Data were retrieved from women treated at the Royal Women’s Hospital for ectopic pregnancy between 2006 and 2012. Only women with minimal symptoms, initial serum β‐hCG ≤5000 IU/L and ectopic mass size of ≤35 mm on ultrasound were included. Two hundred and fifty‐three cases of ectopic pregnancy were analysed.

Results
Initial β‐hCG of women in the study ranged from 18 to 3995 IU/L with a median of 497 (25th to 75th centiles; 222–1160) IU/L. The median levels of β‐hCG levels at day 4, 7 and 14 postmethotrexate injection were 73.8, 47.2 and 10.4% of the initial β‐hCG level, respectively. The 90th centiles of β‐hCG levels at day 4, 7 and 14 were 124.7, 93.8 and 40.0% of initial β‐hCG level, respectively.

Conclusions
Whilst no comparison with those unsuccessfully treated was made, pending further validation studies, the use of these curves may reduce the reliance on specialist units and streamline care for many women with ectopic pregnancy, such as those whose β‐hCG regress in line with centile values without crossing a certain threshold.