Parazzini F, Tozzi L, Bocciolone L, Molteni E, Moreschi C, Fedele L
Instituto di Richerche Farmacologiche Mario Negri, Milano, Italy.
Acta Obstet Gynecol Scand. 1993 Apr;72(3):177-80. doi: 10.3109/00016349309013368.
To analyze risk factors for multiple births.
A case-control study. Cases were 103 women (median age 31 years, range 20-44) who delivered multiple births not related with treatment for infertility at the 'Clinica Luigi Mangiagalli' of Milan. A total of 27 women delivered monozygotic twins and 76 dizygotic ones. Controls were 308 women (median age 30, range 17-45) admitted for normal delivery on selected days to the same clinic where cases had been identified.
Cases tended to be less educated than controls and the relative risk of multiple pregnancy, compared with women reporting seven years of schooling or less, was 0.4 in those reporting 7-11 and 12 or more years of education. When the analysis was done separately for dizygotic and monozygotic multiple pregnancies, this relationship was restricted to dizygotic multiple pregnancies (chi 2 (1) trend for dizygotic pregnancies = 3.82, p = 0.05). A family history of multiple pregnancies was reported in 36 women (48%) with dizygotic multiple pregnancy and 13 (52%) monozygotic ones and 88 (30%) controls. The corresponding relative risks (RR) were 2.2 and 2.5 respectively for dizygotic and monozygotic pregnancies. Compared with nulliparae, the estimated RR of dizygotic multiple pregnancies was 0.5 in women reporting two or more births, but the trend in risk with number of births was not statistically significant. No relationship emerged with spontaneous or induced abortions, body mass index, oral contraceptive or IUD use, age at menarche and risk of multiple pregnancies.
This study confirms the role of familiarity in the risk of multiple pregnancies and suggests some different epidemiological characteristics in dizygotic and monozygotic multiple pregnancies.
分析多胎妊娠的风险因素。
一项病例对照研究。病例为103名女性（中位年龄31岁，范围20 - 44岁），她们在米兰的“Clinica Luigi Mangiagalli”医院分娩多胎，且与不孕症治疗无关。其中27名女性分娩单卵双胞胎，76名分卵双胞胎。对照为308名女性（中位年龄30岁，范围17 - 45岁），她们在选定日期到同一医院进行正常分娩，该医院为病例所在医院。
病例组受教育程度往往低于对照组。与接受7年及以下教育的女性相比，接受7 - 11年教育的女性多胎妊娠相对风险为0.4，接受12年及以上教育的女性多胎妊娠相对风险为0.4。当分别对双卵和单卵多胎妊娠进行分析时，这种关系仅限于双卵多胎妊娠（双卵妊娠的卡方检验（1）趋势 = 3.82，p = 0.05）。36名（48%）双卵多胎妊娠女性、13名（52%）单卵多胎妊娠女性和88名（30%）对照者报告有多胎妊娠家族史。双卵和单卵妊娠的相应相对风险（RR）分别为2.2和2.5。与未生育女性相比，有两次或更多次分娩史的女性双卵多胎妊娠估计RR为0.5，但风险随分娩次数的变化趋势无统计学意义。多胎妊娠风险与自然流产或人工流产、体重指数、口服避孕药或宫内节育器使用、初潮年龄均无关联。
本研究证实了家族因素在多胎妊娠风险中的作用，并提示双卵和单卵多胎妊娠存在一些不同的流行病学特征。
