Neonatal morbidity and mortality in birth centers in the United States 2018-2021: An observational study of low-risk birthing individuals.

Background: Many studies reporting neonatal outcomes in birth centers include births with risk factors not acceptable for birth center care using the evidence-based CABC criteria. Accurate comparisons of outcomes by birth setting for low-risk patients are needed.

Methods: Data from the public Natality Detailed File from 2018 to 2021 were used.

Microstructure and mechanics of the chorioamnion membrane with an emphasis on fracture properties.

The normal mechanical functioning of an intact chorioamnion (CA) membrane is essential to successful human reproduction. The amnion and the chorion, separately and together as the bilayer chorioamnion, serve barrier and container functions throughout gestation, and these two important roles are required from conception to birth. The event associated with the "breaking of waters" is a landmark event in labor and delivery.

Premature rupture of the fetal membranes: is the amnion the major determinant?

Objective: The objective of the study was to evaluate the relative contributions of amnion and chorion to the strength of fetal membranes and to correlate these findings with gestational age.

Study Design: Fetal membranes from 78 pregnancies were tested for biaxial puncture force using a blunt, instrumented probe with a low-force load cell connected through a load cell conditioner to an oscilloscope. The average of 2 to 4 tests performed on independent regions of the membrane was recorded.

Uniaxial stress-relaxation and stress-strain responses of human amnion.

The mechanical behavior of human amnion is examined under uniaxial tensile loading conditions. Monotonic strain-to-failure and stress-relaxation tests are described for membrane strip samples of amnion obtained by removing the chorion cell layer from specimens of whole chorioamnion. The monotonic behavior of the amnion is characterized by a large stress-free strain (approximately 10%) prior to a quadratic load-displacement response.

Mechanical failure of human fetal membrane tissues.

Mechanical integrity of the chorioamnion membrane, and the component chorion and amnion layers, was assessed with biaxial puncture testing. Fetal membranes were obtained from term placentas following labored natural delivery or scheduled cesarean section. Preterm specimens were obtained from deliveries prior to 37 weeks gestation.