It has limited utility for making causal inferences because of multiple threats to internal validity in that it does not adequately address the potential influences of history, maturation, testing effects, instrumentation, regression to the mean, or any interactions between them.
To compare quantitative variables between groups, Mann–Whitney (female vs. male) and Kruskal-Wallis (early, normal or late sexual maturation) tests were used.
Thus, as with any non-experimental pre/post study design, we are unable to account for potential historical, maturation, testing bias that could be responsible for some changes observed.
The efficacy of MMT observed in this study may need to take threats of internal validity into consideration and, namely, the positive outcomes may be caused by other factors such as maturation, testing, and sample selection bias.
The HRP2-based assay is comparable with other techniques because the result produced by this assay has been previously shown to be closely parallel those obtained from the isotopic assay, traditional WHO schizont maturation tests [ 54] and SYBR green I assay [ 56].
This association persisted in multiple linear regression after controlling for type of near-miss and project maturation (t-test, p=0.028), but not when the hospital ID was added to the model instead (t-test, p=0.6).
Such work will likely provide important insights into the simultaneous yet heterogeneous processes that contribute to fetal maturation, providing a broader view of maturation than our currently used fetal maturity tests, which focus solely on the lung.
