Letter to the Editor
Natural Selection in Utero: Evidence from the GreatEast Japan Earthquake
Sir,
We read with great interest the article by Catalanoet al. (2013), in which they used an elegant approach ofautocorrelation to estimate a drop in male births in rela-tion to female births in connection with the Great EastJapan Earthquake of 2011. They concluded that popula-tion stressors can reduce male births via two mechanisms,1) reduced conception of males and 2) increased intrauter-ine loss of male fetuses. We would like to express someconcerns over the latter explanation.
The study by Catalano et al. (2013) did not show anyactual data on spontaneous fetal death number and rateor on preterm births. We would like to focus attention ondata on obstetric outcome relevant to their study. Suga-wara (2012) reported that the Japanese preterm birthrate was reduced (2010, 4.3 %: 2011, 2.8 %) and the abor-tion rate was also reduced (2010, 8.3 %: 2011, 7.5 %) afterthe earthquake even in the Miyagi Prefecture coastareas, those most affected by the disaster. According tothe finding of Catalano et al. the numbers of expectedmales were reduced in June in remainder Japan exclud-ing the most distant and the most affected prefectuturesand also in October in all Japan. The monthly total spon-taneous fetal death numbers in each prefecture after 12weeks of gestation are available from the Japanese Min-istry of Health, Labor and Welfare at http://www.e-stat.-go.jp/SG1/estat/ListE.do?lid5000001101886 (Vol 2, 3).There does not seem to be any increase in fetal deathnumbers in any area during any month in 2011 as com-pared with the previous month of 2010. Catalano et al.(2013) estimated that 2828 males were missing due toreduced conception of males and to increased male fetalloss. If this figure was mainly influenced by male fetalloss, it should have been augmented the observednumbers of spontaneous fetal death after 12 weeks ofgestation. On the contrary results of all Japan in 2011
were reduced (http://www.e-stat.go.jp/SG1/estat/ListE.do?lid5000001101886) (Vol 1, 7-1). Although the numbersincluded legal terminations (abortions) the number of malefetal deaths and the rate of fetal deaths in 2011 in allJapan were reduced as compared to those of 2010 (2010,11796, 24.2: 2011, 11420, 23.9) (Table 1). Moreover, the sexratio of fetal death was also reduced (2010, 2.262: 2011,2.256) (Table 1). Thus at this moment it is not certainwhether the population stressors of the 2011 great earth-quake actually reduce male births via male fetal loss. Fur-ther, we expect that potential other stress factors mayhave affected the outcome. We know there exist missingdata because of the tsunami and there exists only one pre-cise report (Sugawara, 2012) described above. Thereforefurther careful evaluation of such obstetric data is neededin the future.
LITERATURE CITED
Sugawara J Perinatal outcome after Tsunami Disaster. Acta ObstetGynaec Jpn 2012; 64: 1800–3 [in Japanese].
MISAO FUKUDA, KIYOMI FUKUDA
M&K Health Institute30-9 Kariya, Ako, Hyogo 678-0239Japan
TAKASHI SHIMIZU, MIHO NOBUNAGA
2-2-4 Minamiguchi, Takarazuka, Hyogo 665-0011Japan
ANNE GRETE BYSKOV, CLAUS YDING ANDERSEN
Laboratory of Reproductive BiologyJuliane Marie Center for Children,Women and ReproductionRigshospitalet, Section 5712, UniversityHospital of CopenhagenBlegdamsvej 9, DK-2100, Copenhagen, Denmark
DOI: 10.1002/ajhb.22460Published online 17 September 2013 in Wiley Online Library
(wileyonlinelibrary.com).
TABLE 1. The yearly spontaneous and induced fetal death numbers and rates after 12 weeks of gestationand the sex ratios of fetal death in Japan from 2006 to 2011
year Total birth noTotal no of
fetal deaths male female unknownFetal death rate/1000
total birthsSex ratio offetal deaths
2006 1092674 30911 13456 6005 11450 27.5 2.2412007 1089818 29313 12878 5694 10741 26.2 2.2622008 1091156 28177 12381 5498 10298 25.2 2.2522009 1070035 27005 11952 5305 9748 24.6 2.2532010 1071304 26560 11796 5216 9548 24.2 2.2622011 1050806 25751 11420 5061 9270 23.9 2.256
VC 2013 Wiley Periodicals, Inc.
AMERICAN JOURNAL OF HUMAN BIOLOGY 25:859 (2013)
