Department of Obstetrics and Gynecology, Washington University in St. Louis, St. Louis, Missouri 63110, USA.
Obstet Gynecol. 2012 Oct;120(4):753-8. doi: 10.1097/AOG.0b013e318269baac.
To estimate the incidence of placenta previa in twin pregnancies compared with singletons and to estimate the rate and gestational age of previa resolution in twin pregnancies.
This was a retrospective cohort of singleton and twin pregnancies undergoing ultrasonography at 15-22 weeks of gestation and of twin pregnancies undergoing serial ultrasonography from 15 to 40 weeks of gestation. Groups were defined by singleton or twin gestation and by chorionicity of twin gestation. The primary outcomes were incidence of placenta previa in each group and the percentage of all previa resolving at 24-28, 28-32, 32-36, and 36 or more weeks of gestation.
Of 67,895 pregnancies included, 2.1% (1,381 of 65,701) of singleton and 2.5% (56 of 2,194) of twin pregnancies had previa diagnosed (P=.15). Dichorionic twins had an increased risk of placenta previa compared with singletons (adjusted odds ratio 1.54, 95% confidence interval 1.15-2.06) or monochorionic twin pregnancies (relative risk 3.29, 95% confidence interval 1.32-8.21). Of the 1,738 twin pregnancies with serial ultrasound examinations, 51 (2.9%) were noted to have previa. Sixty-nine percent of the previa resolved by 32 weeks, at between 32 and 36 weeks an additional 47% of the remaining previa resolved, and no previa resolved after 36 weeks.
Dichorionic twin pregnancies are at significantly increased risk for ultrasound-diagnosed previa when compared with singleton or monochorionic pregnancies. Among twin pregnancies with previa diagnosed in the second trimester, the majority of cases resolve by 32 weeks.
II.
比较双胞胎妊娠与单胎妊娠的前置胎盘发生率，并估计双胞胎妊娠前置胎盘的消退率及其消退发生的孕周。
本研究为回顾性队列研究，纳入在妊娠 15-22 周行超声检查的单胎妊娠和双胎妊娠，以及在妊娠 15-40 周行连续超声检查的双胎妊娠。根据单胎或双胎妊娠以及双胎妊娠的绒毛膜性对各组进行定义。主要结局为各组前置胎盘的发生率以及 24-28 周、28-32 周、32-36 周和 36 周或以上时所有前置胎盘消退的百分比。
在纳入的 67895 例妊娠中，1%（65701 例中的 1381 例）的单胎妊娠和 2.5%（2194 例中的 56 例）的双胎妊娠被诊断为前置胎盘（P=.15）。与单胎妊娠或单绒毛膜性双胎妊娠相比，双绒毛膜性双胎妊娠发生前置胎盘的风险增加（校正比值比 1.54，95%置信区间 1.15-2.06）。在接受连续超声检查的 1738 例双胎妊娠中，有 51 例（2.9%）被诊断为前置胎盘。69%的前置胎盘在 32 周前消退，在 32-36 周之间，其余前置胎盘中有 47%消退，36 周后没有前置胎盘消退。
与单胎或单绒毛膜性妊娠相比，双绒毛膜性双胎妊娠发生超声诊断的前置胎盘的风险显著增加。在妊娠中期被诊断为前置胎盘的双胎妊娠中，大多数病例在 32 周前消退。
II 级。
