Acid-base differences in preterm and term twin pregnancy

S A Ordorica1, I A Hoskins, B K Young

  • 1Department of Obstetrics and Gynecology, New York University Medical Center.

A prospective study was undertaken which examined 179 sets of twins, 68 premature (less than 36 weeks of gestation) and 111 term. The purpose of this study was to assess differences in the acid-base status between twins related to gestational age, birth order and the time interval between twin births. Although the twin blood-gas data is within the range considered normal, statistically significant differences favoring the first-born were noted for both preterm and term twins. These differences do not depend on gestational age, route of delivery or presentation, and become evident when the interval between twin births exceeds one minute. We postulate that after delivery of the first twin, the reduced uterine size causes a decrease in the intervillous blood flow and consequently a reduction in the respiratory exchange between the second fetus, still in utero, and its placenta.

Related Concept Videos

Acid-Base Titration Curves02:23

Acid-Base Titration Curves

A titration curve is a plot of some solution property versus the amount of added titrant. For acid-base titrations, solution pH is a useful property to monitor because it varies predictably with the solution composition and, therefore, may be used to monitor the titration’s progress and detect its endpoint. Acid-base titration can be performed with a strong acid and a strong base, a strong acid and a weak base, or a strong base and a weak acid.
For a titration carried out for 25.00 mL of 0.100...
Titration of a Weak Acid with a Weak Base01:08

Titration of a Weak Acid with a Weak Base

Weak acids and bases do not undergo dissociation completely, and titrations between these two are rarely studied. When such studies are performed, say, for the titration of a weak acid with a weak base, the titration curve plots the change in pH as a function of the volume of base added. Take the titration of acetic acid with ammonia, for instance. During the titration, these two species form ammonium acetate and water, but the pH change is slow and gradual.
As a result, there is no simple...
Titration of Polyprotic Base with a Strong Acid01:18

Titration of Polyprotic Base with a Strong Acid

The titration of a polyprotic base such as sodium carbonate with a strong acid such as hydrochloric acid results in two equivalence points on the titration curve. At the first equivalence point, the carbonate ions in the base are completely converted to bicarbonate ions. The second equivalence point corresponds to the complete conversion of bicarbonate ions to carbonic acid, which dissociates into carbon dioxide and water. The region before the first equivalence point corresponds to the...
Disorders of Acid-Base Balance01:29

Disorders of Acid-Base Balance

The human body maintains a precise pH range of arterial blood between 7.35 and 7.45. Deviations result in either acidosis (pH < 7.35) or alkalosis (pH > 7.45). These conditions are further classified as respiratory or metabolic disorders based on their underlying cause.
Respiratory Acidosis and Alkalosis
Respiratory acidosis occurs due to an increase in the partial pressure of carbon dioxide PCO2 in the blood. It often arises from shallow breathing or impaired gas exchange caused by...
Diagnosing Acidosis and Alkalosis01:24

Diagnosing Acidosis and Alkalosis

Diagnosing acid-base imbalances involves systematically analyzing arterial blood samples, focusing on three key measurements: pH, bicarbonate (HCO3−) concentration, and carbon dioxide partial pressure (PCO2). This analysis follows a four-step process that helps identify the imbalance's underlying cause and nature.
First, the pH level is assessed to determine whether the blood pH is normal (7.35–7.45), low (acidosis), or high (alkalosis).
Next, the PCO2  and HCO3−  values are examined to...
Acid&#8211;Base Titration: Overview01:26

Acid–Base Titration: Overview

An acid-base titration is a technique used to determine the concentration of an unknown acid or base, using a titrant of known concentration–either a base for acid titration or an acid for base titration. The process involves gradually adding the titrant, leading to a predictable change in the pH of the solution. This change is plotted on a titration curve, showing how a solution's pH varies with the amount of titrant added. Such curves are instrumental in monitoring the titration's progress...