COVID-19 induced birth sex ratio changes in England and Wales.

Background: The sex ratio at birth (male live births divided by total live births) may be a sentinel health indicator. Stressful events reduce this ratio 3-5 months later by increasing male fetal loss. This ratio can also change 9 months after major population events that are linked to an increase or decrease in the frequency of sexual intercourse at the population level, with the ratio either rising or falling respectively after the event. We postulated that the COVID-19 pandemic may have affected the ratio in England and Wales. Methods: Publicly available, monthly live birth data for England and Wales was obtained from the Office for National Statistics up to December 2020. Using time series analysis, the sex ratio at birth for 2020 (global COVID-19 onset) was predicted using data from 2012-2019. Observed and predicted values were compared. Results: From 2012-2020 there were 3,133,915 male and 2,974,115 female live births (ratio 0.5131). Three months after COVID-19 was declared pandemic (March 2020), there was a significant fall in the sex ratio at birth to 0.5100 in June 2020 which was below the 95% prediction interval of 0.5102-0.5179. Nine months after the pandemic declaration, (December 2020), there was a significant rise to 0.5171 (95% prediction interval 0.5085-0.5162). However, December 2020 had the lowest number of live births of any month from 2012-2020. Conclusions: Given that June 2020 falls within the crucial window when population stressors are known to affect the sex ratio at birth, these findings imply that the start of the COVID-19 pandemic caused population stress with notable effects on those who were already pregnant by causing a disproportionate loss of male fetuses. The finding of a higher sex ratio at birth in December 2020, i.e., 9 months after COVID-19 was declared a pandemic, could have resulted from the lockdown restrictions that initially spurred more sexual activity in a subset of the population in March 2020.

COVID-19 onset reduced the sex ratio at birth in South Africa.

Background: The sex ratio at birth (defined as male/(male+female) live births) is anticipated to approximate 0.510 with a slight male excess. This ratio has been observed to decrease transiently around 3-5 months following sudden unexpected stressful events. We hypothesised that stress engendered by the onset of the COVID-19 pandemic may have caused such a decrease in South Africa 3-5 months after March 2020 since in this month, South Africa reported its first COVID-19 case, death and nationwide lockdown restrictions were instituted. Methods: We used publicly available, recorded monthly live birth data from Statistics South Africa. The most recent month for which data was available publicly was December 2020. We analysed live births for a 100-month period from September 2012 to December 2020, taking seasonality into account. Chi-squared tests were applied. Results: Over this 100-month period, there were 8,151,364 live births. The lowest recorded monthly sex ratio at birth of 0.499 was in June 2020, 3 months after March 2020. This June was the only month during this period where the sex ratio inverted i.e., fewer male live births occurred. The predicted June 2020 ratio was 0.504. The observed June 2020 decrease was statistically significant p = 0.045. Conclusions: The sex ratio at birth decreased and inverted in South Africa in June 2020, for the first time, during the most recent 100-month period. This decline occurred 3 months after the March 2020 onset of COVID-19 in South Africa. As June 2020 is within the critical window when population stressors are known to impact the sex ratio at birth, these findings suggest that the onset of the COVID-19 pandemic engendered population stress with notable effects on pregnancy and public health in South Africa. These findings have implications for future pandemic preparedness and social policy.

Influence of the Super Bowl on the United States birth sex ratio.

INTRODUCTION: Many factors have been shown to influence the male to female ratio at birth (M/T). Celebrations increase M/T nine months later, putatively due to elevated coital rates. The Super Bowl (SBS) is consistently held in the first Sunday in February. This study was carried out in order to ascertain whether SBS results in a rise in M/T nine months later, and whether any such changes are influenced by race and census region. METHODS: Births were studied for the period 2003-2015. Seasonality adjustment was applied in order to identify true outlier values over and above those due to natural seasonal M/T variation. RESULTS: This study analysed 53,105,069 births. M/T was elevated in all regions, for all races for 11/2006, 9/2009, 10/2009, 10/2010, 12/2010, 11/2011, 11/2013 and 12/2013. A similar effect is observed in the West Region for all births. For the various ethnic groups, the effect is strongest for Whites in regions Northeast, South and West, and for Black/African American births in regions Midwest and South. DISCUSSION: Events which increase coital activity elevate M/T nine months later as M/T follows a U-shaped regression on cycle day of insemination, with male conceptions occurring more frequently at the beginning (and end) of the menstrual cycle. SBS is a significant annual celebratory event in contemporary American culture. It is possible that increased coital rates during this period (perhaps due to a combination of celebration and inebriation) may result in the M/T rises nine months later observed in this study.

A review of terrorism and its reduction of the gender ratio at birth after seasonal adjustment.

BACKGROUND: Males are born in excess of females, a ratio expressed as M/T (males:total births). The ratio exhibits seasonal variation. Furthermore, acute stressful events may result in a transient dip in male births due to excess foetal losses, reducing M/T. AIMS: This study was carried out in order to identify significant M/T dips after adjusting for seasonality. STUDY DESIGN: Live births by gender and month were sought for acute stressful events. After seasonal correction (where appropriate), M/T dips were sought. SUBJECTS: Live births. OUTCOME MEASURES: M/T dips. RESULTS AND CONCLUSIONS: This paper studied 112,226,306 live births. The following events showed dips ≤5th percentile 3-5months after these acute episodes: the Brooklyn Bridge protests, Katrina Hurricane for all 4 states and for each individual state (Alabama, Florida, Louisiana, Mississippi), the Battle in Seattle, the London bombings, The Madrid bombings (for Madrid and for Spain), the Breivik shooting, the Oklahoma City bombing and the Sandy Hook Elementary School shooting. The Virginia Polytechnic Institute and State University shooting the Fukushima Daiichi nuclear disaster also showed dips albeit slightly later. Seasonal adjustments should be taken into consideration in order to avoid Type 1 or 2 error pitfalls.

EFFECTS OF STRESSFUL EVENTS IN FRANCE (1968) AND JAPAN (1995) ON THE SEX RATIO AT BIRTH.

Males are usually born in excess of females. The sex ratio at birth (SR) is often expressed as the ratio of male to total births. A wide variety of factors have been shown to influence SR, including terrorist attacks, which have been shown to reduce SR. This paper reviews the effects on SR outcomes of the stressful events in France in 1968 (in association with the student and worker riots) and in Japan following the Aum Shinrikyo religious cult's attack on the Tokyo subway using sarin nerve gas in 1995. Both countries displayed seasonal variation in SR. France exhibited a decline in SR in 1968 (p=0.042), with a particularly strong dip in May of that year (p=0.015). For Japan, there was no statistically significant dip for 1995 but there was a significant dip in June of that year (p=0.026). The SR dips follow catastrophic or tragic events if these are perceived to be momentous enough by a given populace. It is believed that SR slumps may be caused by population stress, which is known to lead to the culling of frail/small male fetuses. It has been observed that these fluctuations are comparable in intensity to a substantial proportion of quoted values for perinatal mortality, potentially making this a public health issue.

The President Kennedy assassination and the male to female birth ratio.

INTRODUCTION: Male live births occur slightly in excess of female. This ratio is expressed as M/F. Terrorist attacks induce stress which transiently lowers M/F three to five months later due to increased male foetal losses. A previous study had shown that the assassination of President John F. Kennedy in November 1963 was associated with a significant dip in M/F in the United States for 1964 due to a dip confined to March 1964. This study was carried out in order to ascertain whether the assassination influenced M/F in the rest of the world. METHODS: Annual male and female live births were obtained from a World Health Organisation Mortality database for all countries reporting. Comparisons were made between 1964, the year after the assassination, and the preceding five years (1959-1963) and following five years (1965-1969). Monthly data was only available for Malta, for the period 1958-1968. RESULTS: There were 159,339,564 live births (82,066,005 males, 77,273,559 females, M/F 0.5150; 95% CI 0.5150-0.5151). No dip was present for 1964 for any country, nor for the amalgamation of European countries, for the Far East, the North American continent, or for the amalgamation of the total. Data for Malta showed a significant decline in March 1964 (M/F 0.4661, p=0.0175), translating to a loss of 56 boys (estimated at 6.3/1000 births). DISCUSSION: These findings replicate the findings for the United States following the assassination of President Kennedy. The March M/F dip transiently exceeded the modern expected rate for perinatal mortality, making terrorist attacks Public Health issues.