{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,1]],"date-time":"2026-07-01T04:38:55Z","timestamp":1782880735025,"version":"3.54.5"},"reference-count":79,"publisher":"Wiley","issue":"7","license":[{"start":{"date-parts":[[2023,3,2]],"date-time":"2023-03-02T00:00:00Z","timestamp":1677715200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["American J Hum Biol"],"published-print":{"date-parts":[[2023,7]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Background<\/jats:title><jats:p>This study explores the\u00a0magnitude\u00a0and\u00a0timing\u00a0of\u00a0sex and gender disparities in child development by describing differences in health outcomes for male and female siblings, comparing twins to control for all aspects of life circumstances other than sex and gender.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>We construct a repeat cross\u2010sectional dataset of 191\u2009838 twins among 1.7 million births recorded in 214 nationally representative household surveys for 72 countries between 1990 and 2016. To test for biological or social mechanisms that might favor the health of male or female infants, we describe differences in birthweights, attained heights, weights, and survival to distinguish gestational health from care practices after each child is born.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>We find that male fetuses grow at the expense of their co\u2010twin, significantly reducing their sibling's birthweight and survival probabilities, but only if the other fetus is male. Female fetuses are born significantly heavier when they share the uterus with a male co\u2010twin and have no significant difference in survival probability whether they happen to draw a male or a female co\u2010twin. These findings demonstrate that sex\u2010specific sibling rivalry and male frailty begin in utero, prior to gender bias after birth that typically favors male children.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>Sex differences in child health may have competing effects with gender bias that occurs during childhood. Worse health outcomes for males with a male co\u2010twin could be linked to hormone levels or male frailty, and could lead to underestimates of the effect sizes of later gender bias against girls. Gender bias favoring surviving male children may explain the lack of differences in height and weight observed for twins with either male or female co\u2010twins.<\/jats:p><\/jats:sec>","DOI":"10.1002\/ajhb.23887","type":"journal-article","created":{"date-parts":[[2023,3,3]],"date-time":"2023-03-03T06:59:24Z","timestamp":1677826764000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Sibling rivalry between twins in utero and childhood: Evidence from birthweight and survival of 95\u2009919 twin pairs in 72 low\u2010 and middle\u2010income countries"],"prefix":"10.1002","volume":"35","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3795-3983","authenticated-orcid":false,"given":"Robel","family":"Alemu","sequence":"first","affiliation":[{"name":"Anderson School of Management University of California Los Angeles  Los Angeles California USA"},{"name":"Program in Medical and Population Genetics Broad Institute of MIT and Harvard  Cambridge Massachusetts USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4546-7291","authenticated-orcid":false,"given":"William A.","family":"Masters","sequence":"additional","affiliation":[{"name":"Friedman School of Nutrition Science and Policy Tufts University  Medford Massachusetts USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0573-8699","authenticated-orcid":false,"given":"Amelia B.","family":"Finaret","sequence":"additional","affiliation":[{"name":"Global Academy of Agriculture and Food Systems University of Edinburgh  Edinburgh UK"},{"name":"Department of Global Health Allegheny College  Meadville Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2023,3,2]]},"reference":[{"key":"e_1_2_13_2_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.annepidem.2016.11.011"},{"key":"e_1_2_13_3_1","doi-asserted-by":"publisher","DOI":"10.1093\/qje\/120.3.1031"},{"issue":"3","key":"e_1_2_13_4_1","first-page":"531","article-title":"Sex hormones, immune responses, and autoimmune diseases. Mechanisms of sex hormone action","volume":"121","author":"Ansar Ahmed S.","year":"1985","journal-title":"The American Journal of Pathology"},{"key":"e_1_2_13_5_1","doi-asserted-by":"publisher","DOI":"10.1080\/03014460.2020.1749301"},{"key":"e_1_2_13_6_1","doi-asserted-by":"publisher","DOI":"10.1002\/sim.5419"},{"key":"e_1_2_13_7_1","doi-asserted-by":"publisher","DOI":"10.1186\/s12887-019-1713-2"},{"key":"e_1_2_13_8_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jogc.2021.02.113"},{"key":"e_1_2_13_9_1","doi-asserted-by":"publisher","DOI":"10.1093\/oxfordhb\/9780199389292.013.47"},{"key":"e_1_2_13_10_1","doi-asserted-by":"publisher","DOI":"10.2307\/145671"},{"key":"e_1_2_13_11_1","doi-asserted-by":"publisher","DOI":"10.1162\/003465304323031139"},{"key":"e_1_2_13_12_1","doi-asserted-by":"publisher","DOI":"10.1177\/15648265120333S204"},{"key":"e_1_2_13_13_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jhealeco.2019.05.001"},{"key":"e_1_2_13_14_1","doi-asserted-by":"publisher","DOI":"10.1186\/s12963-020-00229-w"},{"key":"e_1_2_13_15_1","doi-asserted-by":"publisher","DOI":"10.1162\/qjec.122.1.409"},{"key":"e_1_2_13_16_1","doi-asserted-by":"publisher","DOI":"10.1037\/dev0000506"},{"key":"e_1_2_13_17_1","doi-asserted-by":"publisher","DOI":"10.1002\/ajhb.20636"},{"key":"e_1_2_13_18_1","doi-asserted-by":"publisher","DOI":"10.1002\/ajhb.23830"},{"key":"e_1_2_13_19_1","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.1812786116"},{"key":"e_1_2_13_20_1","doi-asserted-by":"publisher","DOI":"10.1093\/ije\/dyab242"},{"key":"e_1_2_13_21_1","doi-asserted-by":"publisher","DOI":"10.1093\/ije\/dyab168.107"},{"key":"e_1_2_13_22_1","doi-asserted-by":"publisher","DOI":"10.2307\/1972764"},{"key":"e_1_2_13_23_1","doi-asserted-by":"publisher","DOI":"10.1002\/ajhb.23648"},{"key":"e_1_2_13_24_1","doi-asserted-by":"publisher","DOI":"10.2307\/2648099"},{"key":"e_1_2_13_25_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ehb.2005.12.001"},{"key":"e_1_2_13_26_1","doi-asserted-by":"publisher","DOI":"10.1002\/ajhb.23595"},{"key":"e_1_2_13_27_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.worlddev.2012.12.001"},{"key":"e_1_2_13_28_1","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.0800221105"},{"key":"e_1_2_13_29_1","doi-asserted-by":"publisher","DOI":"10.1093\/jn\/nxy037"},{"key":"e_1_2_13_30_1","doi-asserted-by":"publisher","DOI":"10.1016\/0277-9536(91)90230-A"},{"key":"e_1_2_13_31_1","doi-asserted-by":"publisher","DOI":"10.1093\/ije\/27.4.657"},{"key":"e_1_2_13_32_1","doi-asserted-by":"publisher","DOI":"10.1375\/twin.6.3.173"},{"key":"e_1_2_13_33_1","doi-asserted-by":"publisher","DOI":"10.1016\/S2352-4642(22)00159-6"},{"key":"e_1_2_13_34_1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0170175"},{"key":"e_1_2_13_35_1","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(03)14237-7"},{"key":"e_1_2_13_36_1","doi-asserted-by":"publisher","DOI":"10.1111\/ppe.12475"},{"key":"e_1_2_13_37_1","unstructured":"Huang Q. Yiwei Q. &Nayga R. M.(2019).Effects of having an opposite\u2010sex twin on labor market outcomes in United States. 2019 Annual Meeting July 21\u201323 Atlanta GA 290991. Agricultural and Applied Economics Association. Retrieved fromhttps:\/\/ideas.repec.org\/\/p\/ags\/aaea19\/290991.html"},{"key":"e_1_2_13_38_1","volume-title":"Demographic and health surveys, various","author":"ICF International","year":"2022"},{"key":"e_1_2_13_39_1","doi-asserted-by":"publisher","DOI":"10.1080\/02724936.1998.11747952"},{"key":"e_1_2_13_40_1","doi-asserted-by":"publisher","DOI":"10.1080\/03014460.2018.1526320"},{"key":"e_1_2_13_41_1","doi-asserted-by":"publisher","DOI":"10.1017\/thg.2016.57"},{"key":"e_1_2_13_42_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41598-018-24634-2"},{"key":"e_1_2_13_43_1","doi-asserted-by":"publisher","DOI":"10.1093\/ije\/29.4.678"},{"key":"e_1_2_13_44_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jhealeco.2015.01.005"},{"key":"e_1_2_13_45_1","doi-asserted-by":"publisher","DOI":"10.1093\/humrep\/dey046"},{"key":"e_1_2_13_46_1","doi-asserted-by":"publisher","DOI":"10.1080\/01621459.1958.10501452"},{"key":"e_1_2_13_47_1","doi-asserted-by":"publisher","DOI":"10.1007\/s13524-020-00909-0"},{"key":"e_1_2_13_48_1","doi-asserted-by":"publisher","DOI":"10.1186\/s12884-018-1694-4"},{"key":"e_1_2_13_49_1","doi-asserted-by":"publisher","DOI":"10.1136\/archdischild-2013-303889"},{"key":"e_1_2_13_50_1","doi-asserted-by":"publisher","DOI":"10.1111\/ppe.12891"},{"key":"e_1_2_13_51_1","doi-asserted-by":"publisher","DOI":"10.1080\/00220389608422446"},{"key":"e_1_2_13_52_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1728-4457.2002.00285.x"},{"key":"e_1_2_13_53_1","doi-asserted-by":"publisher","DOI":"10.1136\/bmj.321.7276.1609"},{"key":"e_1_2_13_54_1","doi-asserted-by":"publisher","DOI":"10.1007\/s10834-016-9506-3"},{"key":"e_1_2_13_55_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.socscimed.2009.02.031"},{"key":"e_1_2_13_56_1","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.0605875104"},{"key":"e_1_2_13_57_1","doi-asserted-by":"publisher","DOI":"10.1017\/S0001566000000088"},{"key":"e_1_2_13_58_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1728-4457.2002.00275.x"},{"key":"e_1_2_13_59_1","doi-asserted-by":"publisher","DOI":"10.1111\/ppe.12534"},{"key":"e_1_2_13_60_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jhealeco.2019.102269"},{"key":"e_1_2_13_61_1","doi-asserted-by":"crossref","unstructured":"Masters W. A. Finaret A. B. & Block S. A. (2022). The economics of malnutrition: Dietary transition and food system transformation.Handbook of Agricultural Economics 4997\u20135083.https:\/\/doi.org\/10.1016\/bs.hesagr.2022.03.006","DOI":"10.1016\/bs.hesagr.2022.03.006"},{"key":"e_1_2_13_62_1","doi-asserted-by":"publisher","DOI":"10.1093\/humrep\/deab029"},{"key":"e_1_2_13_63_1","doi-asserted-by":"publisher","DOI":"10.1257\/aer.90.2.405"},{"key":"e_1_2_13_64_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ehb.2016.07.002"},{"key":"e_1_2_13_65_1","doi-asserted-by":"publisher","DOI":"10.1007\/s13524-012-0161-5"},{"key":"e_1_2_13_66_1","doi-asserted-by":"publisher","DOI":"10.4269\/ajtmh.16-0249"},{"key":"e_1_2_13_67_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jdeveco.2013.01.002"},{"key":"e_1_2_13_68_1","doi-asserted-by":"publisher","DOI":"10.1080\/00220380412331322651"},{"key":"e_1_2_13_69_1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pmed.1001287"},{"issue":"20","key":"e_1_2_13_70_1","first-page":"61","article-title":"More than 100 million women are missing","volume":"37","author":"Sen A.","year":"1990","journal-title":"The New York Review"},{"key":"e_1_2_13_71_1","doi-asserted-by":"publisher","DOI":"10.1080\/17938120.2019.1664837"},{"key":"e_1_2_13_72_1","doi-asserted-by":"publisher","DOI":"10.1017\/S002193201700030X"},{"key":"e_1_2_13_73_1","doi-asserted-by":"publisher","DOI":"10.1080\/00220389008422165"},{"key":"e_1_2_13_74_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.yhbeh.2011.08.011"},{"key":"e_1_2_13_75_1","doi-asserted-by":"publisher","DOI":"10.1080\/17441730.2016.1207930"},{"key":"e_1_2_13_76_1","doi-asserted-by":"publisher","DOI":"10.1126\/science.179.4068.90"},{"key":"e_1_2_13_77_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jhealeco.2014.10.005"},{"key":"e_1_2_13_78_1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0070549"},{"key":"e_1_2_13_79_1","doi-asserted-by":"publisher","DOI":"10.1055\/s-0037-1608876"},{"key":"e_1_2_13_80_1","doi-asserted-by":"publisher","DOI":"10.1186\/1471-2431-7-17"}],"container-title":["American Journal of Human Biology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/ajhb.23887","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/full-xml\/10.1002\/ajhb.23887","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/ajhb.23887","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,11,10]],"date-time":"2023-11-10T12:01:21Z","timestamp":1699617681000},"score":1,"resource":{"primary":{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/10.1002\/ajhb.23887"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,3,2]]},"references-count":79,"journal-issue":{"issue":"7","published-print":{"date-parts":[[2023,7]]}},"alternative-id":["10.1002\/ajhb.23887"],"URL":"https:\/\/doi.org\/10.1002\/ajhb.23887","archive":["Portico"],"relation":{},"ISSN":["1042-0533","1520-6300"],"issn-type":[{"value":"1042-0533","type":"print"},{"value":"1520-6300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,3,2]]},"assertion":[{"value":"2022-11-22","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2023-02-16","order":1,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2023-03-02","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}],"article-number":"e23887"}}