A NEW study shows that a woman’s blood pressure before she gets pregnant could affect whether she conceives a boy or a girl; researchers found those with lower blood pressure tended to have a girl, while higher blood pressure was an indication that a boy was more likely to be conceived.
It is unclear whether one could artificially influence the sex of a baby by deliberately raising or lowering blood pressure, said the paper published in the American Journal of Hypertension.
In the human population as a whole, there is a 50/50 split in the sex ratio, but there are slightly more baby boys born than girls, possibly because baby boys are generally more fragile than girls in early life.
Studies show that boys are 14% more likely to be born premature than girls, and even at the same gestational age boys have a higher risk of death and complications because girls develop faster in the womb. They are more likely to die of infections in infancy, as their immune systems are slightly less mature than girls of the same age.
Although boys catch up with girls developmentally, the human population’s natural sex ratio at birth is 105 boys for every 100 girls, which is seen as nature’s way of balancing out their slightly higher risk of premature death.
But looking at the sex ratios of various countries in Africa, there is more to the story. A country’s sex ratio tell us something about its history, social fabric and economic make-up, if the top five countries on either side of the split in Africa are anything to do by.
Rwanda has the lowest sex ratio in Africa, with just 91.9 men for every 100 women. It means that women outnumber men significantly in the country, partly as a result of the genocide and war in the 1990s.
In the first two years after the 1994 genocide, Rwanda’s adult population was up to 70% female by one estimate, due to the massacre of so many men, and the flight of the (predominantly male) killers over the border into the Democratic Republic of Congo.
Today, most of the refugees have returned into the country, but the horror of the genocide did result in a social transformation that opened the door for women’s participation in public life. In the words of Gregory Warner, writing in this NPR story,”Rwanda was so demolished, so broken, it simply could not rebuild with men’s labour alone.”
Today, Rwanda has the highest percentage of women in parliament in the world, at 64% (a decade and a half ago, it ranked 37th globally in the same indicator, women’s representation in parliament).
Namibia (94.8), Mozambique (95.5) and Senegal (96.5) have the next lowest ratios in Africa, which means like Rwanda, there are more women than men in the country. This is likely to be the result of migration patterns, with more men leaving home to seek better economic fortunes in neighbouring countries or overseas.
In fifth place is South Africa, at 96.8. South Africa is the migration destination for many of the countries in southern Africa, including Namibia and Mozambique above. So why does it have the same skew in its sex ratio?
It is probably the result of HIV/AIDS – which South Africa has in common with Namibia and Mozambique. Although more women than men contract HIV, more men than women die from the disease. Data from UNAIDS shows that despite having lower infection rates than women, men account for 58% of adult AIDS-related deaths in sub-Saharan Africa.
It is the result of hidden social dynamics that make women and girls more vulnerable to infection, but also more likely to get treatment and live longer with HIV compared to men.The same gender norms that make women vulnerable to HIV infection make men less likely to know their status, start treatment, or stick to treatment schedules.
On the flip side, if we look at the top countries that have more men than women, we will also see the effects of social and economic dynamics. Equatorial Guinea has the highest sex ratio in Africa, with 103.5 men for every 100 women.
Oil has something to do with it. Like neighbouring Gabon (also with a male-dominated sex ratio of 102.3), oil wealth has attracted many immigrants, who tend to be male; social dynamics make the emigration of men easier. The two countries have a small population but high demand for labour.
Immigrants from as far afield as Cameroon, Central African Republic, Benin and Mali have emigrated to the two oil economies, attracted by the hopes of personal fortune. The same goes for Nigeria, an oil economy that has a male-skewed sex ratio.
In Cote d’Ivoire’s case, cocoa is the attraction, drawing inmany migrants from neighbouring Burkina Faso and Mali. Cocoa is a very labour-intensive crop, and historically, Mali and Burkina Faso were closely integrated with Cote d’Ivoire. Migration was encouraged to overcome the labour shortages in the Ivorian cocoa economy, and this legacy has continued, as seen by the skewed sex ratio in Cote d’Ivoire.
The same goes for Seychelles, that similarly has a sex ratio tipped in the favour of males, driven by a booming tourism (and related, construction) industry. According to the International Organisation for Migration (IOM), foreigners make up 24% of Seychelles’ workforce, mainly fromIndia, Madagascar, Philippines and Mauritius.
Furthermore, the country’s 2010 census showed that Seychellois women have a higher tendency towards emigration than men, moving to countries like France and the US.