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:12/19/2016)... España y TORONTO , 19 de diciembre de ... Biologics Inc. que permitirá el desarrollo acelerado de MSC-1, un anticuerpo ... varios tipos de tumor en 2017, con múltiples sitios previstos a ... ... con objetivo en el factor inhibidor de leucemia (LIF), una citoquina ...
(Date:12/15/2016)...   WaferGen Bio-systems, Inc. (NASDAQ: ... today that on December 13, 2016, it received a ... Stock Market LLC which acknowledged that, as of December ... stock had been at $1.00 or greater for ten ... Listing Rule 5550(a)(2) of the Nasdaq Stock Market. ...
(Date:12/12/2016)... , Dec. 12, 2016  Researchers at Trinity ... for graphene by combining the material with Silly ... sensitive pressure detector able to sense pulse, blood ... small spider.  The research team,s ... be read here:  http://science.sciencemag.org/content/354/6317/1257 ...
Breaking Biology News(10 mins):
(Date:1/18/2017)...   Boston Biomedical , an industry leader in ... stemness pathways, will feature data from two clinical studies ... ASCO Gastrointestinal Cancers Symposium, held from January 19-21, in ... Napabucasin is an orally-administered investigational agent designed to inhibit ... stem cells (CSCs) possess the property of stemness – ...
(Date:1/18/2017)... ... January 18, 2017 , ... Whitehouse ... expertise. Within Albany Molecular Research, Inc. (AMRI), the scientific staff dedicated to Extractables ... is planned for further growth in 2017. Extractable & Leachable evaluations have become ...
(Date:1/18/2017)... Chicago, IL (PRWEB) , ... January 18, 2017 ... ... auction on January 24th, 2017, to sell research and genetic testing lab equipment ... of service in the Northwest and Northeast regions of the United States. This ...
(Date:1/18/2017)... 18, 2017  Caris Life Sciences, a leading ... the largest private funder of pancreatic cancer research, ... the impact of immunotherapy in the treatment of ... services to identify potential trial candidates based on ... physicians and study investigators. The Lustgarten Foundation is ...
Breaking Biology Technology: