A validated model for predicting live birth after embryo transfer

Abstract

Accurately predicting the probability of live birth and multiple gestations is important for determining a safe number of embryos to transfer after in vitro fertilization. We developed a model that can be fit to individual clinic data for predicting singleton, twin, and total live birth rates after human embryo transfer. The predicted and observed rates of singleton and twin deliveries were compared in a tenfold cross-validation study using data from a single clinic. The model presented accounts for patient age, embryo stage (cleavage or blastocyst), type of transfer cycle (fresh or frozen) and uterine/universal factors. The standardized errors for rates of singleton and twin deliveries were normally distributed and the mean errors were not significantly different from zero (all p > 0.05). The live birth rates per embryo varied from as high as 43% for fresh blastocysts in the 35-year-old age group to as low as 1% for frozen cleavage stage embryos in the 43-year-old age group. This quantitative model or a simplified version can be used for clinics to generate and analyze their own data to guide the number of embryos to transfer to limit the risk of multiple gestations.

Figure 1

Embryo transfer cycles included and excluded.

Figure 2

Embryo transfer models demonstrated for transfer of two embryos. (a) Demonstrates logic for independent embryo implantation and (b) demonstrates logic for independent embryo implantation only when universal factors are favorable. The universal factors fraction is a fraction from 0 (never favorable) to 1 (always favorable). The probability of each outcome is equal to the product of the terms next to the corresponding arrows above and the corresponding terms on the perimeter of the square. For example, the predicted probability of twins in panel b is UNI × $\frac{\text{LBRe}1}{\text{UNI}}$ × $\frac{\text{LBRe}2}{\text{UNI}}$. This same logic can be applied to transfer of more than two embryos. UNI, universal factors fraction; LBR_e1, live birth rate for embryo 1; LBR_e2, live birth rate for embryo 2. This figure is being reproduced from a previous publication.

Figure 3

Live Birth Rate per Embryo for (a) Blastocyst and (b) Cleavage Stage Embryos. 5-year moving groups are used to calculate live birth rates for ages 35 to 43.

Figure 4

Predicted outcomes for (a) Fresh Blastocyst, (b) Fresh Cleavage Stage, (c) Frozen Blastocyst, and (d) Frozen Cleavage Stage Embryo Transfers. The multiples column results are shaded green, yellow, red, or gray to indicate the risk of multiples at delivery (0–9%, 10–19%, 20–29%, or ≥ 30% respectively). LBR, total live birth rate per embryo transfer; % mult., percentage of live deliveries that are multiples; % twins, percentage of live deliveries that are twin deliveries; % trip. or > , percentage of live deliveries that are triplets or greater.