Background <p>In this retrospective observational study, we aimed to evaluate the clinical efficacy and safety of Gu Ben An Tai Decoction (GBATD) combined with dydrogesterone for treating threatened abortion (TA).</p> Methods <p>We retrospectively analysed 66 patients with early TA secondary to spleen and kidney deficiency. The control group received dydrogesterone alone, whereas the observation group received GBATD combined with dydrogesterone. The primary outcome was the rate of successful pregnancy maintenance before 12 weeks of gestation. Additionally, safety profile, time to symptom resolution (vaginal bleeding and/or abdominal pain), laboratory and imaging indicators, and traditional Chinese medicine (TCM) syndrome scores of the two groups were compared. High-performance liquid chromatography-mass spectrometry was used to determine the major composition of GBATD.</p> Results <p>The observation group showed greater increases in serum levels of β-human chorionic gonadotropin, progesterone, estradiol, and Inhibin A than the control group. In contrast, serum cancer antigen 125 levels; uterine artery hemodynamic indices, including systolic/diastolic ratio, pulsatility index, and resistance index; and TCM syndrome scores for spleen and kidney deficiency decreased more significantly in the observation group than in the control group (<i>P</i> &lt; 0.05). The observation group also showed higher rates of effective TCM treatment, overall effectiveness, and successful pregnancy maintenance at 12 weeks than the control group, with statistically significant differences (<i>P</i> &lt; 0.05). GBATD primarily contained 17 components.</p> Conclusion <p>GBATD combined with dydrogesterone effectively treats early TA. It significantly reduces symptoms associated with spleen and kidney deficiency, lowers the miscarriage rate, and causes no evident adverse reactions.</p>