STUDY QUESTION Can women with pregnancy of unknown location (PUL) following in vitro fertilization (IVF) be risk-stratified regarding the subsequent need for medical intervention, based on their demographic characteristics and the results of serum biochemistry at the initial visit? SUMMARY ANSWER The ratio of serum hCG to number of days from conception (hCG/C) or the initial serum hCG level at ≥5 weeks’ gestation could be used to estimate the risk of women presenting with PUL following IVF and needing medical intervention during their follow-up. WHAT IS KNOWN ALREADY In women with uncertain conception dates presenting with PUL, a single serum hCG measurement cannot be used to predict the final pregnancy outcomes, thus, serial levels are mandatory to establish a correct diagnosis. Serum progesterone levels can help to risk-stratify women at their initial visit but are not accurate in those taking progesterone supplementation, such as women pregnant following IVF. STUDY DESIGN, SIZE, DURATION This was a retrospective study carried out at two specialist early pregnancy assessment units between May 2008 and January 2021. A total of 224 women met the criteria for inclusion, but 14 women did not complete the follow-up and were excluded from the study. PARTICIPANTS/MATERIALS, SETTING, METHODS We selected women who had an IVF pregnancy and presented with PUL at ≥5 weeks’ gestation. MAIN RESULTS AND THE ROLE OF CHANCE A total of 30/210 (14.0%, 95% CI 9.9–19.8) women initially diagnosed with PUL required surgical intervention. The hCG/C was significantly higher in the group of women requiring an intervention compared to those who did not (P = 0.003), with an odds ratio of 3.65 (95% CI 1.49–8.89, P = 0.004). A hCG/C <4.0 was associated with a 1.9% risk of intervention, which accounted for 25.7% of the study population. A similar result was obtained by substituting hCG/C <4.0 with an initial hCG level <100 IU/l, which was associated with 2.0% risk of intervention, and accounted for 23.8% of the study population (P > 0.05) LIMITATIONS, REASONS FOR CAUTION A limitation of our study is that it is retrospective in nature, and as such, we were reliant on existing data. WIDER IMPLICATIONS OF THE FINDINGS A previous study in women with PUL after spontaneous conception found that a 2% intervention rate was considered low enough to eliminate the need for close follow-up and serial blood tests. Using the same 2% cut-off, a quarter of women with PUL after IVF could also avoid attending for further visits and investigations. STUDY FUNDING/COMPETING INTEREST(S) No external funding was required for this study. No conflicts of interest are required to be declared. TRIAL REGISTRATION NUMBER N/A.

中文翻译：

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制定用于管理体外受精后未知地点妊娠的单次就诊方案：一项回顾性研究

研究问题 体外受精 (IVF) 后不明部位妊娠 (PUL) 的女性是否可以根据其人口特征和初次就诊时的血清生化结果，对随后是否需要医疗干预进行风险分层？总结答案 血清 hCG 与受孕天数的比率 (hCG/C) 或妊娠 ≥5 周时的初始血清 hCG 水平可用于估计 IVF 后出现 PUL 且在妊娠期间需要医疗干预的女性的风险。跟进。已知信息 在受孕日期不确定且患有 PUL 的女性中，单次血清 hCG 测量不能用于预测最终妊娠结局，因此必须采用系列水平来建立正确的诊断。血清孕酮水平有助于在初次就诊时对女性进行风险分层，但对于服用孕酮补充剂的女性（例如体外受精后怀孕的女性）来说并不准确。研究设计、规模、持续时间 这是一项回顾性研究，于 2008 年 5 月至 2021 年 1 月期间在两个专业早孕评估单位进行。共有 224 名女性符合纳入标准，但 14 名女性未完成随访，被排除在研究之外。参与者/材料、背景、方法 我们选择了 IVF 妊娠并在妊娠 ≥5 周时出现 PUL 的女性。主要结果和机会的作用 共有 30/210 (14.0%, 95% CI 9.9–19.8) 名最初诊断为 PUL 的女性需要手术干预。与不需要干预的女性相比，需要干预的女性组的 hCG/C 显着更高 (P = 0.003)，比值比为 3.65 (95% CI 1.49–8.89，P = 0.004)。hCG/C＜4.0与1.9%的干预风险相关，该人群占研究人群的25.7%。用初始 hCG 水平 <100 IU/l 替代 hCG/C <4.0 得到了类似的结果，这与 2.0% 的干预风险相关，占研究人群的 23.8%（P > 0.05）局限性和谨慎的原因我们研究的局限性在于它本质上是回顾性的，因此我们依赖于现有的数据。研究结果的更广泛意义 之前对自然受孕后患有 PUL 的女性进行的一项研究发现，2% 的干预率被认为足够低，足以消除密切随访和系列血液检查的需要。使用同样的 2% 截止值，四分之一的 IVF 后患有 PUL 的女性也可以避免参加进一步的就诊和检查。研究资助/竞争利益 本研究不需要外部资助。无需声明利益冲突。试用注册号 不适用。