Objective: To identify the association between cervical length (CL) and gestational age at birth. Design: Prospective cohort study. Setting: Seventeen Brazilian reference hospitals. Population: A cohort of 3139 asymptomatic singleton pregnant women who participated in the screening phase of a Brazilian multicenter randomized controlled trial (P5 trial). Methods: Transvaginal ultrasound (TVU) to measure CL was performed from 18 to 22+6 weeks. Women with CL ≤ 30 mm received vaginal progesterone (200 mg/day) until 36 weeks’ gestation. Main Outcome Measures: Area under receive operating characteristic curve (AUC), sensitivity, specificity, Kaplan-Meier curves for preterm birth (PTB), number needed to screen (NNS). Results: CL ≤25mm was associated with extremely severe, severe, moderate and late PTB, whereas a CL 25–30mm was directly associated with late sPTB. The AUC to predict sPTB<28 weeks was 0.82 and for sPTB<34 weeks was 0.67. Almost half of the sPTB occurred in nulliparous women and CL ≤30mm was associated with sPTB <37 weeks (OR = 7.84; 95%CI = 5.5–11.1). The NNS to detect one sPTB <34 weeks in women with CL ≤25mm is 121 and 248 screening tests are necessary to prevent one sPTB <34 weeks using vaginal progesterone prophylaxis. Conclusions: CL measured by TVU is associated with sPTB <34 weeks. Women with CL ≤30mm are at increased risk for late sPTB. Funding: Bill & Melinda Gates Foundation [OPP1107597], the Brazilian Ministry of Health, and the Brazilian National Council for Scientific and Technological Development (CNPq) [401615/20138]. Keywords: cervical length; number needed to screen; preterm birth; short cervix.

Objective: To investigate the incidence of structural and chromosomal abnormalities in cases of fetal oedema on early ultrasound prior to non-invasive prenatal testing (NIPT). Design: Retrospective cohort study. Setting: Tertiary obstetric ultrasound clinic in Melbourne, Australia. Population: Women undergoing pre-NIPT ultrasound examination from January 2013-November 2018 with fetal crown-rump length (CRL) of 28-43 mm. Methods: Cases of reported fetal oedema or increased nuchal thickness were included. Clinical information was collected from the clinic’s patient management database. Oedema was subclassified as isolated nuchal oedema (>2.2 mm) or generalised oedema/hydrops by two operators blinded to pregnancy outcomes. Main Outcome Measures: Incidence of chromosomal or structural defects following the detection of fetal oedema. Results: We identified 104 cases of reported fetal oedema with a CRL between 28-44 mm. Nuchal oedema and generalised oedema were present in 40 (38.5%) and 64 (61.5%) cases respectively. Outcomes were available in 93 cases (89.4%). Relevant chromosomal anomalies were identified in 21.5% (20/93), occurring in 12.1% (4/33) of the nuchal oedema and 26.7% (16/60) of the generalised oedema/hydrops cases. Structural anomalies with normal karyotype were found in an additional four (4.3%) cases. Miscarriage occurred in four (4.3%) cases and termination of pregnancy in 18 cases (19.4%). Oedema resolved by 11-13+6 weeks in 81.9% and these cases had less adverse outcomes than those with NT≥3.5 mm (10.9% vs 76.5%, p<0.001). Conclusions: Fetal oedema in early pregnancy is associated with a high incidence of structural or chromosomal abnormalities, and these rates increase with progressive severity.