Clapp Mark A, Berry Margaret, Shook Lydia L, Roberts Penelope S, Goldfarb Ilona T, Bernstein Sarah N
Department of Obstetrics and Gynecology, Massachusetts General Hospital, Boston, Massachusetts.
Am J Perinatol. 2020 Jan;37(1):86-91. doi: 10.1055/s-0039-1700860. Epub 2019 Nov 18.
To determine the association between low fetal fraction and birth weight among women with a negative cell-free DNA (cfDNA) result for common aneuploidies in the first trimester.
This is a retrospective cohort of women who delivered a singleton between July 2016 and June 2018 at a single institution and had normal cfDNA testing in the first trimester. The primary variable of interest was "low fetal fraction," which was defined as fetal fractions less than 5th percentile among all fetal fractions in the cohort (fetal fraction < 5.34%). The primary outcomes were birth weight ≤ 5th and ≤ 10th percentiles. Multivariable logistic regressions assessed for the association between low fetal fraction and birth weight.
A total of 7,478 women delivered a singleton at ≥24 weeks' gestation, of which 2,387 (32%) underwent genetic screening through cfDNA; the majority were in the first trimester ( = 2,052 [86%]). 2,035 met the inclusion criteria. Birth weight ≤ 5th percentile was significantly higher in the low fetal fraction group (6.9 vs. 3.2%; = 0.04). A low fetal fraction was associated with higher odds of an infant with a low birth weight: adjusted odds ratio (aOR) of 2.32 (95% CI 1.15-4.67) for birth weight ≤ 10th percentile ( = 0.02) and aOR of 3.73 (95% CI 1.40-9.03) for birth weight ≤ 5th percentile ( = 0.004).
Low fetal fractions of ≤ 5th percentile were associated with an increased risk of birth weights ≤ 5th and ≤ 10th percentiles in women with negative cfDNA screening in the first trimester. Future work is needed to further investigate this relationship and to determine the potential clinical implications, such as third-trimester screening for growth restriction in women with low fetal fractions and negative cfDNA screening results.
确定孕早期常见非整倍体游离DNA（cfDNA）检测结果为阴性的女性中，低胎儿游离DNA比例与出生体重之间的关联。
这是一项回顾性队列研究，研究对象为2016年7月至2018年6月在单一机构分娩单胎且孕早期cfDNA检测结果正常的女性。主要研究变量为“低胎儿游离DNA比例”，定义为队列中所有胎儿游离DNA比例中低于第5百分位数的比例（胎儿游离DNA比例<5.34%）。主要结局为出生体重≤第5百分位数和≤第10百分位数。采用多变量逻辑回归分析低胎儿游离DNA比例与出生体重之间的关联。
共有7478名女性在妊娠≥24周时分娩单胎，其中2387名（32%）通过cfDNA进行了基因筛查；大多数在孕早期（n = 2052 [86%]）。2035名符合纳入标准。低胎儿游离DNA比例组中出生体重≤第5百分位数的比例显著更高（6.9%对3.2%；P = 0.04）。低胎儿游离DNA比例与低出生体重婴儿的较高几率相关：出生体重≤第10百分位数时，调整后的优势比（aOR）为2.32（95%CI 1.15 - 4.67）（P = 0.02）；出生体重≤第5百分位数时，aOR为3.73（95%CI 1.40 - 9.03）（P = 0.004）。
孕早期cfDNA筛查结果为阴性的女性中，胎儿游离DNA比例≤第5百分位数与出生体重≤第5百分位数和≤第10百分位数的风险增加相关。未来需要进一步研究这种关系，并确定其潜在的临床意义，例如对胎儿游离DNA比例低且cfDNA筛查结果为阴性的女性在孕晚期进行生长受限筛查。
