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Invisible 9/11 victims: the unborn

Sept. 1, 2006
Special to World Science  

The horrors of Sept. 11, 2001 ap­par­ent­ly trig­gered mis­car­riages of hun­dreds of un­born boys in New York Cit­y, and even more across the Unit­ed States, re­searchers say.

The find­ings are draw­ing at­ten­tion to a phe­no­me­non that sci­en­tists are on­ly be­gin­ning to un­der­stand: the num­ber of boys born in dis­as­ter-struck ar­eas ty­p­i­cal­ly drops as a pe­r­cen­t­age of to­tal births. 

Re­search­ers spe­c­u­lat­e that this might be be­cause a mo­th­er’s stress can kill some fe­tus­es, and that males es­pe­cial­ly are at risk.

The new fin­dings sug­gest such a drop oc­curred dra­mat­i­cal­ly in New York af­ter the Twin Tow­ers tra­g­e­dy: the count of boys born com­pared to girls plunged from rough­ly nor­mal rates to ones un­seen na­tion­al­ly since 1940, when the rec­ord-keep­ing be­gan.

Sci­en­tists at the Uni­ver­si­ty of Cal­i­for­nia, Berke­ley ex­am­ined sta­tis­tics for Jan­u­ar­y, 2002, four months af­ter the at­tacks. They found a five-point drop in the per­cen­tage of male births com­pared to av­er­age.

This helped make that whole year the poor­est for new­born boys of an­y be­tween 1996 and 2004, the lat­est for which fig­ures are avail­a­ble, as cit­y Health De­part­ment sta­tis­tics in­di­cate. These same fig­ures show 999 few­er boys born in that year com­pared to the av­er­age of the oth­er years. There is al­so an an­alo­gous but smaller dip in new­born girls, of 593.

The Berkeley study found that in Jan­u­ar­y of that year, just about the same num­ber of boys and girls were born—an anom­a­ly. Nor­mal­ly there are about 105 ma­le births pe­r 100 fema­le births. A crash in boy births of this mag­ni­tude would cor­re­spond to well over 200 “miss­ing” ba­bies for Jan­u­ar­y alone.

The prob­lem was­n’t lim­it­ed to New York, the Berke­ley researchers said. Pre­vi­ous re­search by them showed a smaller but still no­tice­a­ble dip in ma­le birthrates in far-off Cal­i­for­nia, the De­cem­ber af­ter the dis­as­ter. There, the num­ber fell to un­der 103 ma­le births pe­r 100 fema­le.

Na­tion­wide, fed­er­al sta­tis­tics put ma­le birthrates for the year of the at­tacks at a rec­ord low, bare­ly. But it’s un­known wheth­er the at­tacks were a sig­nif­i­cant fac­tor in that. This would leave un­ex­plained why in New York, the ma­jor rec­orded de­crease did­n’t oc­cur un­til the next year. 

The na­tion­al sta­tis­tics, from the Cen­ters for Dis­ease Con­trol, show 104.6 new­born boys per 100 new­born girls the year of the dis­as­ter, a re­cord low since the gov­ern­ment started keep­ing track in 1940. The se­cond low­est year, one decade earlier, was just a hair higher and rounds off to the same num­ber. Whatever its cause, the low point meant al­most 11,000 boys less than an av­er­age year.  

One ex­pla­na­tion for post-trau­ma short­ages of male ba­bies might be that a spike in a moth­er’s stress hor­mones “in­creases the risk of death among weaker males,” wrote the Berke­ley re­searchers in the May 2005 is­sue of the re­search jour­nal Hu­man Re­pro­duc­tion.

Some sci­en­tists spec­u­late that “these hor­mones pe­rturb ma­les in ges­ta­tion more than fema­les,” they added in the pape­r, which de­scribed the Cal­i­for­nia study. Their more re­cent New York study ap­pears in the jour­nal’s Aug. 26 ad­vance on­line edi­tion.

Higher ma­le vul­ner­a­bil­ity in the womb would mir­ror the fact that boys are weaker than girls as in­fants. The lat­ter ex­plains why boys and girls are typ­i­cal­ly about equal in num­ber by age 5, even though more boys are born: ma­les suf­fer higher in­fant mor­tal­i­ty. 

Sci­en­tists have de­bat­ed why dis­as­ters lead to a drop in the pe­r­cent­age of ma­le births, said the Berke­ley re­searchers, led by Ralph Cata­lano. One the­o­ry holds that such events some­how in­crease the like­li­hood of girls be­ing con­ceived. But the birth­rate changes fol­low­ing Sept. 11 oc­curred much too ear­ly to be ex­plained by that, Cata­lano ar­gued. That would leave the oth­er pos­si­bil­i­ty, that stress killed some fe­tus­es.

Strange­ly, although sud­den di­sast­ers such as earth­quakes seem to pro­duce such ef­fects con­sis­tent­ly, pro­longed hard­ships
such as wars and po­ver­ty don’t, the re­search­ers noted—so the role of stress, if any, is not sim­ple.

* * *

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The 2001 World Trade Center attacks apparently triggered miscarriages of hundreds of unborn boys in New York City, and even more across the United States, researchers say. Past studies have noted that the number of baby boys born in areas struck by natural disasters typically drops as a percentage of total births. Scientists speculated that this might be because a mother’s stress can somehow kill weaker fetuses, and that males are especially vulnerable. New research has found that the effect appeared dramatically in New York after the Twin Towers tragedy: the number of newborn boys compared to girls plunged from roughly normal rates to levels lower than any seen nationally since 1940, when authorities started keeping records. Scientists at the University of California at Berkeley examined birthrate statistics for January, 2002, four months after the attacks. The dip in male births contributed to making that year the poorest for newborn boys of any year between 1996 and 2004, the latest for which figures are available, as documented in city health department statistics. These same figures show 999 fewer boys born in that year compared to the average of the other years. There is also a corresponding but smaller drop in newborn girls, of 593. The study found that in January of that year, just about the same number of boys and girls were born, a dramatic anomaly. Normally there are about 105 male births per 100 female births, both in New York and nationwide, consistent with global averages. The crash in boy births the researchers recorded would correspond to more than 200 “missing” babies for January alone. The problem wasn’t limited to New York, the Berkeley group argued. Previous research by the same team showed a smaller but still noticeable dip in male birthrates in far-off California, the December after the disaster. There, the number fell to under 103 male births per 100 female. Nationwide, federal statistics show that male birthrates for the year of the attacks at a record low, barely. But it’s unknown whether the attacks were a significant factor in that: this would leave unexplained why in New York, the major recorded decrease didn’t occur until the following year. The national statistics, from the Centers for Disease Control, show 104.6 newborn boys per 100 newborn girls the year of the disaster, the lowest since the government started keeping track in 1940. The previous record, a decade before the tragedy, was barely a hair higher and rounds off to the same number. One explanation for the shortages of male babies is that a spike in a mother’s stress hormones “increases the risk of death among weaker males,” wrote the Berkeley researchers in the May 2005 issue of the research journal Human Reproduction. Some scientists speculate that “these hormones perturb males in gestation more than females,” they added in the paper, which described the California study. Their more recent New York study appears in the journal’s Aug. 26 advance online edition. Increased male vulnerability in the womb would mirror the well-known fact that boys are weaker than girls as infants. That fact explains why males suffer higher infant mortality, and thus why boys and girls are typically about equal in number by age 5, even though more boys are born. Scientists have debated why disasters lead to a drop in the percentage of male births, said the Berkeley researchers, led by Ralph Catalano. One theory holds that such events somehow increase the likelihood of girls being conceived. But the decreases that his group identified occurred much too early to be explained by that, Catalano argued—leaving the other possibility, that stress killed some fetuses.