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Accuracy of the Chinese lunar calendar method to predict a baby's sex: A population-based study
Abstract
We estimated the accuracy of a non-invasive, inexpensive method (the Chinese lunar calendar, CLC) to predict the sex of a baby from around the time of conception, using 2,840,755 singleton births occurring in Sweden between 1973 and 2006. Maternal lunar age and month of conception were estimated, and used to predict each baby's sex, according to a published algorithm. Kappa statistics were estimated for the actual vs. the CLC-predicted sex of the baby. Overall kappa was 0.0002 [95% CI -0.0009, 0.0014]. Accuracy was not modified by year of conception, maternal age, level of education, body mass index or parity. In a validation subset of 1000 births in which we used a website-customised algorithm to estimate lunar dates, kappa was -0.02 [95% CI -0.08, 0.04]. Simulating the misuse of the method by failing to convert Gregorian dates into lunar did not change the results. We conclude that the CLC method is no better at predicting the sex of a baby than tossing a coin and advise against painting the nursery based on this method's result.
... Our study is in complete agreement with what Villamor et al has brought out in their study that predicting a baby's sex by Chinese lunar calendar is no more accurate than flipping a coin. 8 There is a hypothesis that ovum itself may give chemical signal or chemoattractant and select the type of sperm that may fertilize a particular ovum and may result in a particular gender of the foetus. As has been concluded in one of the review articles by Skandhan et al in 2011. ...
Background: The relation of lunar phases at the time of conception to the sex of the child at birth has been touted as a method of sex selection by various birth calendars with controversial results. It is made to believe that indeed there is a relation of lunar phase at the time of conception/intercourse which results in birth of a particular gender. The purpose of this study was to examine the influence of the lunar phase on the possible relationship between lunar position at EDD/LMP and the gender of the child.Methods: One thousand and five deliveries were retrospectively analysed from 1 January 2016 to 31 December 2018 at the department of obstetrics and gynaecology of military hospital, Gwalior (latitude and longitude coordinates: 26.218287, 78.182831). Females having regular menstrual periods history around conception and in general their periods have been normal and regular were included in the study. Females having irregular menstrual periods history or having oligomenorrhoea/polymenorrhoea, ART/IVF conceptions were excluded from the study. Exact lunar phases were determined at the time of EDD and not with their LMP since that would automatically corelate well with LMP because of regularity of their periods. The actual date of birth was not considered while corelating with moon phase because of obvious reason of unexpected timing of labour.Results: The analysis revealed no significant correlation of gender of the child to lunar phases at EDD. This would indirectly corelate well with the LMP since the inclusion criterion had females having normal and regular menstrual periods.Conclusions: There is no predictable influence of the lunar phase on the gender of the baby. As expected, and in agreement with some recent studies this pervasive myth is not evidence based.
Facultative adjustment of sex ratios by mothers occurs in some animals, and has been linked to resource availability. In mammals, the search for consistent patterns is complicated by variations in mating systems, social hierarchies and litter sizes. Humans have low fecundity, high maternal investment and a potentially high differential between the numbers of offspring produced by sons and daughters: these conditions should favour the evolution of facultative sex ratio variation. Yet little is known of natural mechanisms of sex allocation in humans. Here, using data from 740 British women who were unaware of their foetus's gender, we show that foetal sex is associated with maternal diet at conception. Fifty six per cent of women in the highest third of preconceptional energy intake bore boys, compared with 45% in the lowest third. Intakes during pregnancy were not associated with sex, suggesting that the foetus does not manipulate maternal diet. Our results support hypotheses predicting investment in costly male offspring when resources are plentiful. Dietary changes may therefore explain the falling proportion of male births in industrialized countries. The results are relevant to the current debate about the artificial selection of offspring sex in fertility treatment and commercial 'gender clinics'.
There is a large research literature on the variation of human sex ratio (proportion of males at birth) with (1) time of insemination within the mother's fruitful cycle (TWC), (2) duration of gestation (DOG), (3) coital frequency, here called 'coital rate' (CR) and (4) duration of time taken to achieve conception in a period of risk (viz. in the absence of birth limitation methods) (TTC). The variation of sex ratio with each of these four variables has usually been treated as a discrete topic. Consider the four propositions that each of these sorts of variation exists. Here it is argued that these propositions entail one another to varying degrees, and that, for that reason, empirical failures to detect (at conventional levels of significance) one such form of variation (as e.g. with time to conception) should not justify rejecting the hypothesis that such variation exists until the whole network of propositions has been considered. Evidence that offspring sex ratio varies with time of conception within the cycle is strong. It is argued here that, as a consequence, the available data constitute evidence that sex ratio varies with CR and with time to achieve conception, although this variation is small, difficult to detect and of no clinical significance. Lastly, sex ratio varies substantially with DOG, though the explanation for this is not established: it is suggested that the present treatment provides a testable framework for such an explanation.
To investigate whether interpregnancy maternal weight change (difference between body mass index [BMI] at the first antenatal visit of the second pregnancy and BMI at the first antenatal visit of the first pregnancy) or changes in smoking status between pregnancies is related to the sex ratio of the second pregnancy.
Population-based cohort study.
Swedish Birth Registry.
A total of 220,889 women who had their first two consecutive singleton births between 1992 and 2004. Both live births and stillbirths were included.
Analyses of data collected prospectively in nationwide registries.
Male-to-female sex ratio of the second pregnancy.
The sex ratio of the second pregnancy increased linearly with the amount of maternal weight change from the first to the second pregnancies, from 1.024 in women who lost more than 1 unit BMI to 1.080 in women who gained 3 or more units. This association was independent of obstetric complications, length of the interpregnancy interval, and maternal sociodemographic characteristics at the second pregnancy. Change in maternal smoking status from the first to the second pregnancies was not significantly related to the sex ratio of the second pregnancy.
There could be a causal relation between prepregnant maternal weight gain and the sex ratio of the offspring.