Some maternal infections, contracted before or during pregnancy, can be transmitted to the fetus, during gestation (congenital infection), during labor and childbirth (perinatal infection) and through breastfeeding (postnatal infection). The agents responsible for these infections can be viruses, bacteria, protozoa, fungi. Among the viruses most frequently responsible for congenital infections are Cytomegalovirus (CMV), Herpes simplex 1–2, Herpes virus 6, Varicella zoster. Moreover Hepatitis B and C virus, HIV, Parvovirus B19 and non-polio Enteroviruses when contracted during pregnancy may involve the fetus or newborn at birth. Recently, new viruses have emerged, SARS-Cov-2 and Zika virus, of which we do not yet fully know the characteristics and pathogenic power when contracted during pregnancy.

Viral infections in pregnancy can damage the fetus (spontaneous abortion, fetal death, intrauterine growth retardation) or the newborn (congenital anomalies, organ diseases with sequelae of different severity). Some risk factors specifically influence the incidence of transmission to the fetus: the timing of the infection in pregnancy, the order of the infection, primary or reinfection or chronic, the duration of membrane rupture, type of delivery, socio-economic conditions and breastfeeding. Frequently infected neonates, symptomatic at birth, have worse outcomes than asymptomatic. Many asymptomatic babies develop long term neurosensory outcomes.

The way in which the virus interacts with the maternal immune system, the maternal-fetal interface and the placenta explain these results and also the differences that are observed from time to time in the fetal‑neonatal outcomes of maternal infections. The maternal immune system undergoes functional adaptation during pregnancy, once thought as physiological immunosuppression. This adaptation, crucial for generating a balance between maternal immunity and fetus, is necessary to promote and support the pregnancy itself and the growth of the fetus. When this adaptation is upset by the viral infection, the balance is broken, and the infection can spread and lead to the adverse outcomes previously described. In this review we will describe the main viral harmful infections in pregnancy and the potential mechanisms of the damages on the fetus and newborn.

一些在怀孕前或怀孕期间感染的母体感染可以在妊娠期间（先天性感染）、分娩和分娩期间（围产期感染）以及通过母乳喂养（产后感染）传染给胎儿。造成这些感染的因素可以是病毒、细菌、原生动物、真菌。最常引起先天性感染的病毒包括巨细胞病毒 (CMV)、单纯疱疹病毒 1–2、疱疹病毒 6 和水痘带状疱疹病毒。此外，在怀孕期间感染乙型和丙型肝炎病毒、艾滋病毒、细小病毒 B19 和非脊髓灰质炎肠道病毒可能会感染胎儿或出生时的新生儿。最近出现了新的病毒，SARS-Cov-2和寨卡病毒，我们还不完全了解它们在怀孕期间感染时的特征和致病力。

妊娠期病毒感染可损害胎儿（自然流产、胎死腹中、宫内发育迟缓）或新生儿（先天性异常、器官疾病及严重程度不同的后遗症）。一些风险因素特别影响向胎儿传播的发生率：妊娠期感染的时间、感染顺序、原发感染或再感染或慢性感染、胎膜破裂持续时间、分娩类型、社会经济条件和母乳喂养。经常感染的新生儿，出生时有症状，其结果比无症状的更差。许多无症状的婴儿会出现长期的神经感觉结果。

病毒与母体免疫系统、母胎界面和胎盘相互作用的方式解释了这些结果，以及在母体感染的胎儿-新生儿结局中不时观察到的差异。母体免疫系统在怀孕期间经历功能适应，曾被认为是生理性免疫抑制。这种适应对于在母体免疫力和胎儿之间产生平衡至关重要，对于促进和支持妊娠本身以及胎儿的生长是必要的。当这种适应被病毒感染打乱时，平衡就会被打破，感染就会传播并导致前面描述的不良后果。