Independent risk factors for twin pregnancy adverse fetal outcomes before 28 gestational week by first trimester ultrasound screening

Abstract

Background: The incidence of multiple pregnancies has increased worldwide recently and women with a twin pregnancy are at higher risk of adverse outcomes compared with women with a singleton pregnancy. It is important to understand the risk factors for adverse fetal outcomes in twin pregnancy in order to guide clinical management.

Aim: To identify the independent risk factors, including maternal personal and family medical histories and first trimester ultrasound screening findings, for adverse fetal outcomes of twin pregnancy before 28 weeks of gestation.

Methods: The data of 126 twin pregnancies in our hospital, including pregnancy outcomes, first trimester ultrasound screening findings and maternal medical history, were retrospectively collected. Twenty-nine women with adverse outcomes were included in the abnormal group and the remaining 97 women were included in the control group.

Results: Patients in the abnormal group were more likely to be monochorionic diamniotic (13/29 vs 20/97, P= 0.009), with a higher mean pulsatility index (PI, 1.57 ± 0.55 vs 1.28 ± 0.42, P = 0.003; cutoff value: 1.393) or a higher mean resistance index (0.71 ± 0.11 vs 0.65 ± 0.11, P = 0.008; cutoff value: 0.683) or early diastolic notch of bilateral uterine arteries (UtAs, 10/29 vs 15/97, P = 0.024) or with abnormal ultrasound findings (13/29 vs 2/97, P < 0.001), compared with the control group. Monochorionic diamnioticity, higher mean PI of bilateral UtAs and abnormal ultrasound findings during first trimester screening were independent risk factors for adverse fetal outcomes (P < 0.05).

Conclusion: First trimester ultrasound screening for twin pregnancy identifies independent risk factors and is useful for the prediction of fetal outcomes.

Keywords: First trimester ultrasound screening; Monochorionic diamniotic twin; Pulsatility index; Twin pregnancy; Uterine artery.

Figure 1

Twin pregnancy ultrasound scan at the 13 + 2 gestational week. A: A dichorionic diamniotic twin pregnancy with two placentas and two distinct amniotic cavities; B: Fetus A with normal ultrasound findings; C: Fetus B with omphalocele shown on crown-rump length section as a mass protrusion of the intestine and liver through a navel hernia in the abdominal wall; D: Color Doppler showed that the blood supply of the mass was from Fetus B. CRL: Crown-rump length; NT: Nuchal translucency.

Figure 2

Receiver operating characteristic curve for mean pulsatility index of bilateral uterine arteries and mean resistance index of bilateral uterine arteries. The area under the receiver operating characteristic (ROC) curve of mean pulsatility index (PI) of bilateral uterine arteries (UtAs; blue line) was 0.650 with a Youden index of 0.309 and the cutoff value as 1.393. The area under the ROC curve of mean resistance index (RI) of bilateral UtAs (pink line) was 0.661 with a Youden index of 0.319 and the cutoff value as 0.683. Mean PI of bilateral UtAs larger than 0.650, or mean RI larger than 1.393 suggested a higher risk of adverse fetal outcomes. ROC: Receiver operating characteristic; PI: Pulsatility index; RI: Resistance index.