Type 1 IFNs interfere Zika pregnancy complications

Researchers from the Yale University School of Medicine in New Haven examined the role of type 1 IFNs in limiting or mediating ZIKV disease within a model of congenital infection, observed after ZIKV infection of type I IFN receptor knockout ( ifnar1 −/− ) dams mating with wild-type sires, resulting in fetuses with functional type 1 IFN signaling.

Pregnant dams carried a mixture of fetuses that expressed or did not express IFN-α/β receptor (IFNAR) ( ifnar1+/− and ifnar1 −/− ) within the same uterus. The researchers found that the titer of virus replication was higher in the placenta of ifnar1 −/− than ifnar1 +/− . Only ifnar1 +/− fetuses were resorbed after ZIKV infection during early pregnancy; ifnar1 −/− littermates continued to develop.

IFNAR signaling in the conceptus was found to inhibit development of the placental labyrinth, resulting in abnormal maternal-fetal barrier architecture after ZIKV infection. Exposure of midgestation human chorionic villous explants to type I IFN resulted in altered placental morphology and cytoskeletal rearrangements within the villous core; this was not seen with exposure to type III IFN.

The results implicate type I IFNs as a possible mediator of pregnancy complications, including spontaneous abortions and growth restriction, in the context of congenital viral infections.
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Labour induction at 40 weeks reduces risk of perinatal death

Induction of labor at 40 weeks in nulliparous women aged 35 and older is associated with reduced risk of in-hospital perinatal death, induction at or near the due date may be safer than expectant management in this group. Guidelines recommend induction of labor between 41 and 42 weeks of gestation to prevent the risks associated with prolonged pregnancy.

Women having their first baby at age 35 years or over are at increased risk of pregnancy complications, including perinatal death. To better understand the risks and benefits of elective induction in this group, researchers analyzed a national database of mothers giving birth between 2009 and 2014.

They discovered that induction of labour at 40 weeks (compared with expectant management) was associated with a lower risk of in-hospital perinatal death (0.08% versus 0.26%; adjusted risk ratio [adjRR] 0.33; 95% confidence interval [CI] 0.13-0.80, P = 0.015) and meconium aspiration syndrome (0.44% versus 0.86%; adjRR 0.52; 95% CI 0.35-0.78, P = 0.002).

Induction at 40 weeks was also associated with a slightly increased adjusted risk of instrumental vaginal delivery (adjRR 1.06; 95% CI 1.01-1.11, P = 0.020) and emergency caesarean section (adjRR 1.05; 95% CI 1.01-1.09, P = 0.019). The number needed to treat (NNT) analysis indicated that 562 (95% CI 366-1,210) inductions of labor at 40 weeks would be required to prevent 1 perinatal death. Bringing forward the routine offer of induction of labour from the current recommendation of 41-42 weeks to 40 weeks of gestation in this group of women may reduce overall rates of perinatal death.
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