By 20 weeks, which becomes a major contributor to amniotic fluid?

By 20 weeks, which becomes a major contributor to amniotic fluid?

• A. Fetal urine
• B. Maternal blood plasma
• C. Lung secretions
• D. Placental fluid

Answer: (A)

Amniotic fluid source shifts as gestation progresses, and by midpregnancy the fetus itself becomes the main supplier. Early in pregnancy the fluid largely comes from maternal plasma crossing the membranes, but as the fetal kidneys mature and begin producing urine, that urine is released into the amniotic cavity. By around 20 weeks the volume of amniotic fluid is predominantly determined by fetal urine output, making it the major contributor. The fetus also swallows and reabsorbs fluid, which helps regulate volume, but the direct and continuous production of urine overtakes other sources. Lung secretions and placental fluid contribute only minor amounts in comparison. Maternal blood plasma is no longer the direct major source at this stage.

Amniotic fluid source shifts as gestation progresses, and by midpregnancy the fetus itself becomes the main supplier. Early in pregnancy the fluid largely comes from maternal plasma crossing the membranes, but as the fetal kidneys mature and begin producing urine, that urine is released into the amniotic cavity. By around 20 weeks the volume of amniotic fluid is predominantly determined by fetal urine output, making it the major contributor. The fetus also swallows and reabsorbs fluid, which helps regulate volume, but the direct and continuous production of urine overtakes other sources. Lung secretions and placental fluid contribute only minor amounts in comparison. Maternal blood plasma is no longer the direct major source at this stage.