Human reproduction
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Despite the widespread use of highly effective contraceptive methods in France, one in every three pregnancies is unintended. Among women experiencing an unintended pregnancy leading to an abortion, half had changed their contraceptive method in the 6 months preceding the abortion, in most cases switching to a less-effective method or to no method at all. This study provides estimates of method-specific contraceptive discontinuation rates for any reason and for method-related reasons among French women. ⋯ Contraceptive discontinuation rates among French women are substantially lower than those reported for US women. Comparing the determinants of contraceptive discontinuation and the role of healthcare providers in helping women make these changes would improve our understanding of the reasons for such variation.
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Common knowledge of over a century has it that monozygotic and dizygotic twinning events occur by unrelated mechanisms: monozygotic twinning 'splits' embryos, producing anomalously re-arranged embryogenic asymmetries; dizygotic twinning begins with independent ovulations yielding undisturbed parallel embryogeneses with no expectation of departures from singleton outcomes. The anomalies statistically associated with twin births are due to the re-arranged embryos of the monozygotics. Common knowledge further requires that dizygotic pairs are dichorionic; monochorionicity is exclusive to monozygotic pairs. ⋯ Dizygotic twinning and monozygotic twinning have the same list of consequences of anomalous embryogenesis. Those include an unignorable fraction of dizygotic pairs that are in fact monochorionic, plus many more sharing co-twins' cells in tissues other than a common chorion. The idea that monozygotic and dizygotic twinning events arise from the same embryogenic mechanism is the only plausible hypothesis that might explain all of the observations.