Navigation Links
Weight gain between first and second pregnancies associated with increased odds of male second child
Date:9/24/2007

Boston, MA -- A slightly greater number of males than females are born worldwide every year. In recent decades, although there are still more baby boys born than girls, there has been an apparent decline in the ratio of male to female newborns in several industrialized countries, including Canada, Denmark, England, Germany, Japan and the United States. That has led researchers to ask: Are there any factors that can influence the probability of giving birth to a baby boy or girl? A new study from the Harvard School of Public Health (HSPH) and Karolinska Institutet in Stockholm, Sweden, found that mothers who experienced an increase in weight from the beginning of the first pregnancy to the beginning of the second pregnancy may be slightly more likely to give birth to a baby boy during their second pregnancy. The study appears online September 24, 2007 in the journal Fertility & Sterility.

The results are provocative because few biological factors are known in humans to influence the chances of either conceiving or carrying to term a baby boy or girl. Our study suggests that maternal nutritional factors might play a role, said Eduardo Villamor, assistant professor of international nutrition at HSPH and lead author of the study.

Some prior studies had looked at what factors might influence the sex ratio, but evidence of causality has been weak. Parental smoking, for example, has been associated with both lower and higher sex ratios. Maternal nutritional status had been studied, but there was little evidence to support a causal relationship with the sex ratio. One of the hypotheses that the authors of this study wanted to test was whether the increase in maternal obesity in several industrialized countries could play a role in the declining sex ratio. Their study found the opposite--maternal weight gain seemed to favor the birth of boys.

The study population, drawn from the Swedish Birth Registry, included 220,889 women who had successive pregnancies between 1992 and 2004 (live births and stillbirths were included). The researchers analyzed the change in womens body mass index (BMI) between the first and second pregnancies. (BMI is weight in kilograms divided by the square of height in meters.) The male to female sex ratio of the second pregnancy increased linearly with the amount of weight change from the first to second pregnancy, from 1.024 in women who lost more than 1 unit BMI to 1.080 in women who gained 3 or more units (a male to female sex ratio of 1.000 would indicate an equal number of boys and girls being born). The trend was independent of obstetric complications, maternal smoking, parental age, length of the interpregnancy interval and the sex or survival status of the first-born child.

The data suggest that interpregnancy weight gain appears related to a slight increase in the probability of giving birth to a baby boy during a second pregnancy. The obesity epidemic does not appear to explain the observed decline in the sex ratio in some industrialized countries, which indicates that there are factors still unknown influencing the probability of giving birth to boys or girls.

The authors are careful to note that women should not gain weight to try to influence the sex of their baby. Weight gain before pregnancy carries significant risks to the mother and the baby, and should not be practiced to influence the odds of having a boy, said Villamor. Other factors of which weight gain is only an indicator could be at play here.


'/>"/>

Contact: Todd Datz
tdatz@hsph.harvard.edu
617-432-3952
Harvard School of Public Health
Source:Eurekalert

Related biology news :

1. Research may provide new link between soft drinks and weight gain
2. Leptin-signaling Protein Maintains Normal Body Weight And Energy Balance In Mice
3. Weight control protein may yield antiobesity drugs
4. Eating, body weight regulated by specific neurons
5. An essential regulator of body weight revealed
6. Engineers discover why toucan beaks are models of lightweight strength
7. Weighting cancer drugs to make them hit tumors harder
8. Its not fair! We are programmed to resist weight loss
9. Just like us, social stress prompts hamsters to overeat, gain weight
10. Very low birth weight linked to reduced quality of life in pre-school children
11. 76 percent of workers older than 60 years of age are overweight or obese
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/20/2016)... MINNETONKA, Minn. , Jan. 20, 2016   ... that supports the entire spectrum of clinical research, is ... in 2015. MedNet,s significant achievements are the result of ... of) iMedNet eClinical , it,s comprehensive, ... --> --> Key MedNet growth ...
(Date:1/15/2016)... , Jan. 15, 2016 Recent publicized ... small to find new ways to ensure data security ... iOS and Android that ties ... biometrics, transforming it into a hardware authorization token. Customer ... swipe their fingerprint on their KodeKey enabled device to ...
(Date:1/11/2016)... Jan. 11, 2016 Synaptics Incorporated (NASDAQ: ... today announced that its ClearPad ® TouchView ™ ... won two separate categories in the 8 th ... Best Technology Breakthrough. The Synaptics ® TDDI solution ... supply chain, thinner devices, brighter displays and borderless designs. ...
Breaking Biology News(10 mins):
(Date:2/12/2016)... SAN DIEGO , Feb. 12, 2016 Biocom, ... life science community, took a group of San ... as part of its 2016 Precision Medicine Advocacy Fly-In. ... at the Food and Drug Administration (FDA), the Centers for ... (NIH), as well as San Diego U.S. Representatives Susan ...
(Date:2/12/2016)... MedGenome,s Commitment Will Help ... of Complex Diseases Such as Cancer, Metabolic Disorders, ... --> --> MedGenome, the market ... leading provider of genomics research services globally, today ... GenomeAsia 100K consortium as a founding member. ...
(Date:2/11/2016)... Germany and GERMANTOWN, Maryland ... QGEN ; Frankfurt Prime Standard: QIA) today announced the ... Panels for gene expression profiling, expanding QIAGEN,s portfolio of ... panels enable researchers to select from over 20,000 human ... discover interactions between genes, cellular phenotypes and disease processes. ...
(Date:2/11/2016)... ... February 11, 2016 , ... ... delivering cutting-edge information focused on the development and manufacture of biopharmaceuticals and ... premier sponsor of the 2016 BioProcess International Awards – Recognizing Excellence in ...
Breaking Biology Technology: