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In the first trimester, the main sources of amniotic fluid are fetal lung secretions, transportation of maternal plasma across the fetal membranes, and the surface of the placenta. By the second trimester, the fetal kidneys start to produce urine which becomes the main source of the amniotic fluid for the remainder of the pregnancy. [4]
In the case that the fluid does not reaccumulate, the reduction of amniotic fluid stabilizes the pregnancy. Otherwise, the treatment is repeated as necessary. There is no standard procedure for how much fluid is removed each time. There is a danger that if too much fluid is removed, the recipient twin could die.
Leaking or rupture of membranes: Leaking or rupture of membranes may be caused by a gush of fluid or a slow constant trickle of fluid. This is due to a tear in the membrane. Premature rupture of membranes can also result in low amniotic fluid levels. Placental problems: Placental problems may cause low amniotic fluid. If the placenta is not ...
Amniotic fluid is removed from the mother by an amniocentesis procedure, where a long needle is inserted through the abdomen into the amniotic sac, using ultrasound guidance such that the fetus is not harmed. Amniocentesis is a low risk procedure, with risk of pregnancy loss between 1 in 1,500 – 1 in 700 procedures.
It is characterized by changes in fetal movement, growth, heart rate, and presence of meconium stained fluid. [4] Risk factors for fetal distress/non-reassuring fetal status include anemia, restriction of fetal growth, maternal hypertension or cardiovascular disease, low amniotic fluid or meconium in the amniotic fluid, or a post-term pregnancy.
During pregnancy the plasma volume increases by 40-50% and the red blood cell volume increases only by 20–30%. [22] These changes occur mostly in the second trimester and prior to 32 weeks gestation. [24] Due to dilution, the net result is a decrease in hematocrit or hemoglobin, which are measures of red blood cell concentration.
Fetal urine production begins in early gestation and comprises the majority of the amniotic fluid in the second and third trimesters of pregnancy. The fetus continuously swallows amniotic fluid, which is reabsorbed by the gastrointestinal tract and then reintroduced into the amniotic cavity by the kidneys via urination.
The presence of a "T-sign" at the inter-twin membrane-placental junction is indicative of monochorionic-diamniotic twins (that is, the junction between the inter-twin membrane and the external rim forms a right angle), whereas dichorionic twins present with a "lambda (λ) sign" (that is, the chorion forms a wedge-shaped protrusion into the ...