Table 2.
List of predictions and relevant model parameters that test them. The column on the right indicates qualitative support for each prediction. Note that for Predictions 1 and 2, the main effects of parity (β1) are the most pertinent tests; negative correlations (ρ) between residuals or mother-level intercepts of parity and outcomes would indicate energetic tradeoffs, but caused by some unobserved variable rather than by parity itself.
| Prediction | Relevant parameters in the model | Supported? |
|---|---|---|
| 1: Tradeoff fertility maternal health (‘cost of reproduction’) |
β1: Negative association of parity with nutritional status and body shape ρ: Negative correlations (  ) between residuals of parity ( and nutritional status ( and for mother-level random intercepts for parity ( and nutritional status ( ; the same for body shape |
Unable to test |
| 2: Tradeoff fertility offspring health (‘quantity–quality tradeoff’) |
β1: Negative association of parity with birth weight, birth length, live birth, gestational age, placenta weight, and head circumference ρ: Negative correlation (  ) between residuals of parity ( and birth weight ( and for mother-level random intercepts for parity ( and birth weight ( ; the same for other offspring outcomes |
No (Fig. 1) |
| 3: Reduced tradeoff with greater access to resources | Other βs: interactions between parity and SEP, year, height, age of menarche, marital status in predicting mother and offspring outcomes, such that negative effect of parity is weaker for women with better current conditions (higher SEP, married, later years) or conditions experienced during their development (taller women, women with earlier menarche) | No (Fig. 2) |
| 4: Higher overall fitness with greater access to resources | Other βs: higher SEP, being married, taller height and earer age of menarche associated with higher parity, controlling for year (and thereby prevalent social norms) | Mixed (Fig. 3) |
| Further expected associations | Other βs: negative association between twin birth, male sex and mother and offspring outcomes | Unable to test/yes (Fig. 4) |