Abstract
Based on a 1900 census sample of 34,166 post-reproductive females (> or =45 years), the birth month effect was put to the test, for both lifetime fertility as well as child survival, controlling for maternal birth cohort (1826-1835, 1836-1845, 1846-1855), Duncan's SEI, urbanity, nativity, literacy and marital duration. Testing for potential cohort effects did not indicate a temporal trend in fertility by maternal birth month (seasonal Mann-Kendall test, p=0.578), while a minute increase in offspring survival was detected (p<0.001, Sen's estimator of slope=0.02, 95% CI=0.02 to 0.03). Further analyses of the maternal birth month effect on child survival were therefore seized. For lifetime fertility, ANOVA results indicated that maternal birth month was a major predictor for total offspring count (F11, 33606=1809.0, p<0.001), accounting for 37.2% of the total variability. In addition to main effects, a statistically significant interaction effect was observed (F538, 33606=2.2, p<0.001), with a corresponding effect size of eta2=0.40. Planned contrasts revealed that birth-month-specific differences in fertility achieved statistical significance (F11, 31798=1712.9, p<0.001), while post-hoc multiple comparisons for literacy and nativity displayed an inverse relationship with fertility, which meets demographic expectations. Controlling for all factors of interest, models of cohort-specific offspring counts (independent ANOVAs for 1826-1835: F157, 3467=26.3, p<0.001; 1836-1845: F182, 10299=75.5, p<0.001; 1846-1855: F199, 19859=137.9, p<0.001) indicated that women born in the first half of the year (particularly, January, February, April and May) achieved above-average parity, while those born in the latter half (namely, July, October, November and December) displayed markedly lower fertility averages. These monthly disparities are in line with previous observations and appear to be linked to seasonal optimal ripening of the oocyte or seasonal preovulatory over-ripeness ovopathy (Jongbloet, 1992).
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
