External validation of a frequently used prediction model for ongoing pregnancy in couples with unexplained recurrent pregnancy loss

Abstract STUDY QUESTION What is the predictive performance of a currently recommended prediction model in an external Dutch cohort of couples with unexplained recurrent pregnancy loss (RPL)? SUMMARY ANSWER The model shows poor predictive performance on a new population; it overestimates, predicts to...

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Bibliographic Details
Published in:Human reproduction (Oxford) 2022-03, Vol.37 (3), p.393-399
Main Authors: Youssef, A, van der Hoorn, M L P, Dongen, M, Visser, J, Bloemenkamp, K, van Lith, J, van Geloven, N, Lashley, E E L O
Format: Article
Language:English
Subjects:
Abortion, Habitual - diagnosis
Abortion, Habitual - etiology
Adult
Female
Humans
Male
Maternal Age
Pregnancy
Pregnancy Outcome
Pregnancy Rate
Retrospective Studies
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Summary:Abstract STUDY QUESTION What is the predictive performance of a currently recommended prediction model in an external Dutch cohort of couples with unexplained recurrent pregnancy loss (RPL)? SUMMARY ANSWER The model shows poor predictive performance on a new population; it overestimates, predicts too extremely and has a poor discriminative ability. WHAT IS KNOWN ALREADY In 50–75% of couples with RPL, no risk factor or cause can be determined and RPL remains unexplained. Clinical management in RPL is primarily focused on providing supportive care, in which counselling on prognosis is a main pillar. A frequently used prediction model for unexplained RPL, developed by Brigham et al. in 1999, estimates the chance of a successful pregnancy based on number of previous pregnancy losses and maternal age. This prediction model has never been externally validated. STUDY DESIGN, SIZE, DURATION This retrospective cohort study consisted of 739 couples with unexplained RPL who visited the RPL clinic of the Leiden University Medical Centre between 2004 and 2019. PARTICIPANTS/MATERIALS, SETTING, METHODS Unexplained RPL was defined as the loss of two or more pregnancies before 24 weeks, without the presence of an identifiable cause for the pregnancy losses, according to the ESHRE guideline. Obstetrical history and maternal age were noted at intake at the RPL clinic. The outcome of the first pregnancy after intake was documented. The performance of Brigham’s model was evaluated through calibration and discrimination, in which the predicted pregnancy rates were compared to the observed pregnancy rates. MAIN RESULTS AND THE ROLE OF CHANCE The cohort included 739 women with a mean age of 33.1 years (±4.7 years) and with a median of three pregnancy losses at intake (range 2–10). The mean predicted pregnancy success rate was 9.8 percentage points higher in the Brigham model than the observed pregnancy success rate in the dataset (73.9% vs 64.0% (95% CI for the 9.8% difference 6.3–13.3%)). Calibration showed overestimation of the model and too extreme predictions, with a negative calibration intercept of −0.46 (95% CI −0.62 to −0.31) and a calibration slope of 0.42 (95% CI 0.11–0.73). The discriminative ability of the model was very low with a concordance statistic of 0.55 (95% CI 0.51–0.59). Recalibration of the Brigham model hardly improved the c-statistic (0.57; 95% CI 0.53–0.62) LIMITATIONS, REASONS FOR CAUTION This is a retrospective study in which only the first pregnancy a
ISSN:0268-1161
1460-2350
DOI:10.1093/humrep/deab264