First child soon after the wedding is more likely to be a son

The research of Dr. Ilona Nenko and Dr. Grażyna Jasieńska of the Institute of Public Health, Jagiellonian University Medical College in Kraków, is of unique importance because it is based on old parish records.

"We have retraced the history of 377 marriages in the years 1782-1882 in one of the rural parishes in the Island Beskids - Dr. Nenko told PAP. They have a unique value, because they are well-preserved and detailed, and they are maintained to this day.

The data collected in parish records show that in this period women who had their first pregnancies earlier, also had subsequent pregnancies more quickly. They had more children, and generally more sons than daughters.

"In the past, when modern contraceptives were not available, the time elapsed from the wedding to the birth of the first child was largely the indication of the women's fertility. Today, we are more interested in how long the couple has been trying to have the first child" - emphasised Dr. Nenko.

How to explain that? Woman's fertility largely depends on her nutrition. The better it is, the higher the level of sex hormones, which in turn makes it easier to become pregnant - said Dr. Nenko. She added that having a boy is more energy-consuming for the woman's body. Thus, the relationship between the time to first pregnancy and the ultimate number of sons.

First pregnancy time data also have an inverse relationship, indicating the woman’s condition. Even for women who lived more than two hundred years ago.

Researchers from Kraków intend to continue the research on the basis of the same parish records. "In the next stage of the analysis we want to determine whether in the case of women having more children affects the length of their life" - said Dr. Nenko PAP. Pregnancy is a heavy burden on the body. Hence the assumption that giving birth to more children could shorten a woman's life.

Source: PAP - Science and Scholarship in Poland, Zbigniew Wojtasiński