Association between fetal fraction at the second trimester and subsequent spontaneous preterm birth

To evaluate the association between the fetal fraction of cell-free DNA at the second trimester and subsequent spontaneous preterm birth.

In this retrospective cohort study, data were collected from women with singleton pregnancies who underwent noninvasive prenatal testing at 14 to 25 weeks of gestation. The eligible patients were classified into three groups according to pregnancy outcome: birth at ≥37 weeks of gestation (term group), delivery at <34 weeks of gestation (early spontaneous preterm), and delivery at 34⁺⁰ to 36⁺⁶  weeks of gestation (late spontaneous preterm). Stepwise linear regression was performed to determine the maternal characteristics associated with the fetal fraction of cell-free DNA. Logistic regression was used to determine the relationship between the fetal fraction of cell-free DNA and pregnancy outcomes by adjusting for history of preterm birth.

A total of 8129 singleton pregnancies met the recruitment criteria. Among them, 7790 (95.83%) were in the term group, 284 (3.49%) were in the late spontaneous preterm group, and 55 (0.68%) were in the early spontaneous preterm group. The fetal fraction of cell-free DNA was negatively correlated with body mass index, maternal age, nulliparity, and history of spontaneous preterm birth; positively correlated with gestational age; and not correlated with assisted reproduction or surface antigen of hepatitis B virus (HBsAg) positivity. After adjusting for history of preterm birth, a logistic regression analysis demonstrated no statistically significant associations between the fetal fraction of cell-free DNA and spontaneous preterm birth in any of the preterm groups (<34 weeks, 34⁺⁰ to 36⁺⁶  weeks, and <37 weeks).

Our preliminary study found no relationship between the fetal fraction on NIPT at the second trimester and subsequent spontaneous preterm birth.