Patumanond Jayanton, Tawichasri Chamaiporn, Khunpradit Suthit
Academic Division of Clinical Epidemiology and Medical Statistics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
Gend Med. 2010 Feb;7(1):55-63. doi: 10.1016/j.genm.2010.01.001.
Shoulder dystocia (ShD) and cephalopelvic disproportion (CPD) share some common risk factors. Whether infant male sex is an independent risk factor for ShD, or if the risk is confounded by other known factors, is uncertain.
The aim of this study was to explore the unconfounded effect of infant male sex on the risk for ShD and its interaction with other risk factors compared with CPD.
A retrospective data analysis was conducted of deliveries in Lamphun Hospital, Lamphun, Thailand. All vaginal deliveries complicated by ShD were collected as ShD cases. All labors terminated by cesarean delivery (CD) due to CPD were collected as CD/CPD cases. Vaginal deliveries that took place immediately before or after the index ShD cases were collected as controls. Multivariable adjusted odds ratios (AORs) for infant male sex and its 95% CI in cases of ShD and CD/CPD were computed by multichotomous logistic regression controlling for other obstetric risks. The effects of maternal height, gestational age, and birth weight on the risk for ShD or CD/CPD among male or female infants was also explored. Stability of the effect of the risk between male and female infants was tested with Chow tests.
Thirty-five ShD cases and 199 CD/CPD cases were collected, as were 586 controls. Infant male sex was a significant independent risk factor for ShD (AOR = 5.00; 95% CI, 1.83-13.61; P = 0.002), but not for CD/CPD (AOR = 1.09; 95% CI, 0.75-1.59; P = NS). For CD/CPD, the effects of maternal height, gestational age, and birth weight were similar for male and female infants, but the corresponding effect on ShD was more pronounced in male than in female infants (P < 0.001 for all comparisons).
Infant male sex is a risk factor for ShD independent of other known risks. Male sex also amplified the existing effects of short maternal height, extended gestational age, and greater birth weight. If infant sex is known to be male before delivery, the obstetrician may consider avoiding vaginal delivery in mothers who have other strong risks for ShD.
肩难产（ShD）和头盆不称（CPD）有一些共同的风险因素。男婴是否是ShD的独立风险因素，或者该风险是否被其他已知因素混淆，尚不确定。
本研究的目的是探讨男婴对ShD风险的无混杂影响，以及与CPD相比，其与其他风险因素的相互作用。
对泰国南奔府南奔医院的分娩情况进行回顾性数据分析。所有并发ShD的阴道分娩均作为ShD病例收集。所有因CPD而行剖宫产（CD）终止妊娠的产妇均作为CD/CPD病例收集。将索引ShD病例之前或之后立即发生的阴道分娩作为对照收集。通过多分类逻辑回归控制其他产科风险，计算ShD和CD/CPD病例中男婴的多变量调整优势比（AOR）及其95%置信区间（CI）。还探讨了母亲身高、孕周和出生体重对男婴或女婴发生ShD或CD/CPD风险的影响。用Chow检验检验男婴和女婴风险效应的稳定性。
收集到35例ShD病例、199例CD/CPD病例以及586例对照。男婴是ShD的显著独立风险因素（AOR = 5.00；95%CI，1.83 - 13.61；P = 0.002），但不是CD/CPD的独立风险因素（AOR = 1.09；95%CI，0.75 - 1.59；P = 无统计学意义）。对于CD/CPD，母亲身高、孕周和出生体重对男婴和女婴的影响相似，但对ShD的相应影响在男婴中比在女婴中更明显（所有比较P < 0.001）。
男婴是ShD的风险因素，独立于其他已知风险。男性性别也放大了母亲身高矮、孕周延长和出生体重较大等现有风险的影响。如果在分娩前已知婴儿性别为男性，产科医生可能会考虑避免在有其他ShD强烈风险因素的母亲中进行阴道分娩。
