- Previously, numerous theories have linked maternal characteristics to the presence of a male or female fetus.
- None of these theories have been conclusively supported by robust scientific evidence.
- But a recent theory states that a woman's blood pressure before pregnancy is associated with her likelihood of delivering a boy or a girl.
A new paper suggests that a woman's likelihood of giving birth to a boy or girl is linked to the blood pressure before pregnancy.
None of the theories relating to maternal characteristics to the presence of a male or female fetus has been conclusively supported by robust scientific evidence.
‘Higher maternal blood pressure before pregnancy emerged as an independent predictor of subsequently delivering a boy.’
These observations raise the possibility that there may be certain physiological features in women that relate to a woman's likelihood of sex-specific fetal loss and hence her likelihood of delivering a boy or girl.
For the study, the researchers established a pre-conception cohort consisting of young women who were planning to get pregnant
They used the model to evaluate the relationship between maternal pre-pregnancy health and the sex of the baby.
Researchers led by Dr. Ravi Retnakaran, endocrinologist at Mount Sinai Hospital in Toronto, and an investigator with the Lunendfeld-Tanenbaum Research Institute, began the study in 2009.
They recruited 3375 married women from Liuyang, China.
Among them 1692 women were assessed for blood pressure, cholesterol, triglycerides, and glucose.
Researchers excluded 281 women as they were potentially pregnant at their baseline assessment.
The final study population for the analysis consisted of 1411 women who were assessed for anthropometry and measurement of blood pressure, cholesterol, triglycerides, and glucose at median 26.3 weeks before pregnancy.
Each woman was followed across the pregnancy up to delivery after she became pregnant.
The women delivered 739 boys and 672 girls.
Researchers found that the systolic blood pressure before pregnancy was higher in women who delivered a boy than in those who had a girl (112.5 mm Hg vs. 109.6 m).
After adjustment for covaroates like age, education, smoking, BMI, waist, LDL cholesterol, HDL cholesterol, triglycerides and glucose, the mean adjusted systolic blood pressure before pregnancy was found to be higher in women who subsequently had a boy than in those who delivered a girl (106.0 mm Hg vs. 103.3 mm Hg).
Higher maternal blood pressure before pregnancy emerged as an independent predictor of subsequently delivering a boy.
According to Retnakaran, this "suggests that a woman's blood pressure before pregnancy is a previously unrecognized factor that is associated with her likelihood of delivering a boy or a girl."
"This novel insight may hold implications for both reproductive planning and our understanding of the fundamental mechanisms underlying the sex ratio in humans." Retnakaran added.
The paper "Maternal Blood Pressure before Pregnancy and Sex of the Baby: A Prospective Preconception Cohort Study" is published in the American Journal of Hypertension
- Ravi Retnakaran et al. Maternal Blood Pressure Before Pregnancy and Sex of the Baby: A Prospective Preconception Cohort Study. American Journal of Hypertension ; (2017) doi.org/10.1093/ajh/hpw165