Amniotic Fluid Regulation PDF

Amniotic Fluid Regulation Andrea Shelton, DNP, APRN, CNM Spring 2024 Definition Amniotic Fluid Liquid surrounding fetus after first few weeks of gestation and throughout intrauterine development Derived almost entirely from fetus throughout most of pregnancy Functions Cushions and protects fetus aga...

Amniotic Fluid Regulation Andrea Shelton, DNP, APRN, CNM Spring 2024 Definition Amniotic Fluid Liquid surrounding fetus after first few weeks of gestation and throughout intrauterine development Derived almost entirely from fetus throughout most of pregnancy Functions Cushions and protects fetus against trauma Antibacterial properties to protect against infections Provides space for fetal movement and growth Reservoir capacity provides short-term source of fluid and nutrients to fetus Maintains consistent temperature and pressure Necessary for fetal lung, musculoskeletal, and gastrointestinal development First Trimester: Embryonic – Early Fetal Period https://medicine.en-academic.com/363/A mnion Embryo resides in two fluid-filled sacs - exocoelomic and inner amniotic cavity – that contain large amounts of liquid Coelomic fluid fills exocoelomic cavity beginning at 7 weeks Maximum volume at 10 weeks, then disappears by 12-14 weeks Coelomic fluid composition is similar to maternal plasma and different from amniotic fluid Amniotic cavity contains amniotic fluid Early fetal period established fetal contribution to fluid volume regulation Amniotic Fluid Development Fetal urine enters amniotic cavity Fetus swallows amniotic fluid Small daily volume flows Lungs begin secreting liquid Second Trimester Mid to Late Fetal Gestation Sonography and animal models have help inform source and composition of amniotic fluid during latter half of gestational period Production and clearance sources involved in amniotic fluid regulation https://www.instagram.com/medictests/p /C3Qf6 AIu2jN / Production Sources Major Primarily produced by fetus in form of urine and lung liquid Minor Secretions from fetal oralnasal cavities https://www.jaypeedigital.com/book/9788184485912/chapter/ch8 Clearance Sources Major Fetal swallowing and intramembranous pathway Minor Transmembranous pathway https://vectormine.com/item/ fetal-wa ter-flow-and-amnio tic -fluid-with-ana tomic al-structure-out line-diagram / Transmembranous Pathway Route for exchange of water and solute products between amniotic fluid and maternal blood across the decidua and myometrium (uterine wall) Occurs between maternal and fetal compartments Image adapted from previous PowerPoint; Farah E, Thornton P. Intramembranous Pathway Route characterized by all passage exchanges between amniotic fluid and fetal blood that may occur across other surfaces (e.g. fetal skin, umbilical cord) Water moves from one fetal compartment to another via microscopic fetal vessels Key factor in fluid volume homeostasis Role of aquaporins in fluid resorption Image adapted from previous PowerPoint; Farah E, Thornton P. Amniotic Fluid Regulation Volume does not significantly change on a daily basis Amniotic fluid itself constantly cycles fluid in and out of amniotic cavity via production and removal and is completed replaced in 24 hours at approximately 1000 mL/day Amount on fluid in third trimester varies Little change from 24 weeks to until near term, then begins to decrease after 40 weeks gestation Daily Amniotic Volume Flows Near Term Fetus Fetal urine production 800-1200 mL/day Fetal lung liquid secretion 170 mL/day Fetal swallowing 500-1000 mL/day Intramembranous flow 200-400 mL/day Oral-nasal secretions 25 mL/day Transmembranous flow 10 mL/day https ://obgy nk ey.c om/amniotic-fluid-volume/ https ://midwifethink ing.c om/2013/08 /14/a mnio tic-fluid-volume- too-much-too-li ttle-or-who-knows/ Risk Factors Insufficient Fluid Excess Fluid Pregnant person: Pregnant person: Hyperglycemia Dehydration Fetus Severe hypertension Obstructed swallowing Renal disorders Cardiac failure Fetus Severe anemia Urinary/renal abnormalities Heart disease Growth restriction Amniotic Fluid Volumes as Function of Gestational Age Beall, Marie & van den Wijngaard, Jeroen & van Gemert, Martin & Ross, Michael. (2012). Water Flux and Amniotic Fluid Volume: Understanding Fetal Water Flow. Nephrology and Fluid/Electrolyte Physiology. 3-18. 10.1016/B978-1-4377-2658-9.00001-7. Summary Amniotic fluid is essential for normal fetal growth and development Abnormalities many indicate disease of fetus, pregnant person, or both and are associated with adverse perinatal outcomes Volume starts to decrease around term pregnancy period, and can lead to risks associated with reduced volume in late- to post-term periods Measurement is passive reflector of fetal condition Definition Oligohydramnios Polyhydramnios Normal AFI: 6—23 cm Normal DVP: 2-8 cm AFI 5 cm or less DVP 2 cm or less AFI 24 cm or greater DVP 8 cm or greater Amniotic Fluid Assessment AFI: Amniotic fluid index DVP: Deepest Vertical Pocket (single deepest pocket sometimes referred to as “Maximum Vertical Pocket” or “MVP” or “Single Deepest Vertical Pocket” or “SVDP”) Subjective assessment Various factors influencing results Fetal position and/or movement experience level of ultrasound examiner Equipment quality Hydration status https://www.invitra.com/en/amniotic -f luid/a mniot ic-fluid-assessment/ Cho HC, Sun S, Min Hyun C, Kwon JY, Kim B, Park Y, Seo JK. Automated ultrasound assessment of amniotic fluid index using deep learning. Med Image Anal. 2021 Apr;69:101951. doi: 10.1016/j.media.2020.101951. Epub 2021 Jan 7. PMID: 33515982. Jha P, Raghu P, Kennedy AM, Sugi M, Morgan TA, Feldstein V, Pōder L, Penna R. Assessment of Amniotic Fluid Volume in Pregnancy. Radiographics. 2023 Jun;43(6):e220146. doi: 10.1148/rg.220146. PMID: 37200220. Oligohydramnios Clinical Findings: Uterine size is small for gestational age Fundal height is less than weeks of gestation by >3 OR Incidental finding on prenatal ultrasound Diagnostic criteria: Based on sonographic visualization of decreased amniotic fluid volume Single deepest pocket 24 cm Polyhydramnios May be idiopathic or related to maternal and/or fetal disorder Incidence rate: 1-2% Homeostatic mechanisms of amniotic fluid regulation more successful at prevention polyhydramnios vs oligohydramnios Approximately 40% is idiopathic Recurrence of 6.6-fold increase with history of idiopathic polyhydramnios Fetal anomalies  1 in 3 Diabetes for pregnant person  8-25% Twin-twin transfusion syndrome  up to 10% Uncommon causes: aneuploidy, high cardiac output states, neuromuscular disorders, Bartter syndrome Fetal growth restriction is associated with high morbidity and mortality when combined with polyhydramnios Possible Adverse Outcomes Respiratory compromise of pregnant person Prelabor rupture of membranes Preterm labor and birth Fetal malposition Macrosomia (and possibly shoulder dystocia) Umbilical cord prolapse Abruption Longer second stage of labor Postpartum hemorrhage (risk for uterine atony) Antepartum Management Etiology Severity Symptoms Antepartum Management Severe Mild idiopathic No RCTs to demonstrate quality evidence-based strategies and standards for care Possibility for spontaneous resolution Guidelines vary Weekly BPP until birth Consider amnioreduction for symptom improvement Indomethacin to reduce urine production Polyhydramnios Delivery timing Intrapartum Care Management Depends on severity and etiology Caution with cervical ripening and labor induction methods Interval confirmation of cephalic presentation Continuous electronic fetal monitoring Rupture of membranes between vs. during contractions Possible needle amniotomy in OR Appropriate emergency preparation APRN/CNM Role SCREEN DIAGNOSE COLLABORATE COMMUNICATE/SUPPORT REFER