OG Updates

·         The reduced gastrointestinal motility during pregnancy has been thought to be due to increased circulating levels of progesterone. However, recent evidence suggests that elevated estrogen concentrations mediate the effect by enhancing nitric oxide release from the nonadrenergic noncholinergic nerves that modulate gastrointestinal motility. Gastric emptying has generally been considered to be slowed during pregnancy; however, via indirect methods some researchers have shown no changes in gastric emptying rates in women in the first or second trimesters or at term. Transit time of food through the gastrointestinal tract may be slowed so much that more water than normal is reabsorbed, leading to constipation.

·         Prothrombin (factor II) is only slightly affected by pregnancy, if at all. Some investigators have noted small increases; others have reported normal values. Recent studies have also noted mild increases in factor V, and suggest a thrombinlike influence on the activity of factor V. Factor XI decreases slightly toward the end of pregnancy, and factor XIII (fibrin-stabilizing factor) is appreciably reduced, up to 50% at term.

·         The physiologic hypertrophy of the pituitary gland is associated with an increase in the number of pituitary lactotroph cells at the expense of the somatotropic cell types. Thus, growth hormone secretion is depressed during the second half of pregnancy and the early puerperium. Because levels of circulating insulin-like growth factor (IGF-1) increase throughout pregnancy, a placental growth hormone has been postulated and recently identified. Maternal levels of IGF-1 correlate highly with this distinct placental growth hormone variant but not placental lactogen during pregnancy and in the immediate puerperium.

·         Ultrasound has had a continuous evolution over the last 20 years, with better equipment being produced each year. Real-time sonography allows a 2-D image to demonstrate fetal anatomy, as well as characteristics such as fetal weight, movement, volume of amniotic fluid, and structural anomalies such as myomas or placenta previa which may affect the pregnancy. 3-D sonography allows volume to be ascertained, creating a three-dimensional appearing image on the 2-D screen, which assists in identifying certain anatomical anomalies. Most recently, 4-D machines have been developed, which produce a 3-D image in real time.

·         Recent studies of the uterine artery early diastolic notch have demonstrated its usefulness as another marker for fetal well-being.

·         Maternal diabetes, whether it is gestational, chemical, or insulin-dependent, is the condition classically associated with fetal macrosomia. It was long assumed that fetal macrosomia could be accounted for by the “Pedersen hypothesis”—ie, that the condition was due to inadequate management of diabetes during pregnancy. Initial reports suggested that careful control of blood glucose in insulin-dependent diabetic women would prevent fetal macrosomia, but recent studies have suggested that the problem is not so simple and that the incidence may correlate better with cord blood concentrations of maternally acquired anti-insulin IgG antibodies, and/or increased serum levels of free fatty acids, triglycerides, and the amino acids alanine, serine, and isoleucine.

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·         Preeclampsia is hypertension associated with proteinuria and edema, occurring primarily in nulliparas after the 20th gestational week and most frequently near term. Recent data support the elimination of edema as a diagnostic criterion. Eclampsia is the occurrence of seizures that cannot be attributed to other causes in a preeclamptic patient.

·         While early studies failed to show a significant increase in cerebrospinal fluid (CSF) magnesium concentrations during therapy, more recent studies have shown about a 20% increase in CSF magnesium levels, and these levels parallel those in the serum. Magnesium sulfate decreases the amount of acetylcholine released at the neuromuscular junction, resulting in peripheral neuromuscular blockade at high magnesium concentrations; however, this does not account for its anticonvulsant effect. A recent study demonstrated that magnesium sulfate had a central anticonvulsant effect on electrically-stimulated hippocampal seizures in rats. The researchers speculated that since magnesium ion blocks calcium entry into neurons through the N-methyl-D-aspartate (NMDA) receptor–operated calcium channel, magnesium sulfate might be acting through this mechanism. On the other hand, another study found that magnesium sulfate was ineffective in altering seizure discharge in pentylenetetrazole-induced status epilepticus in rats. These researchers argued that because magnesium blocks calcium entry through the NMDA receptor–operated calcium channel in a voltage-dependent manner, it would be ineffective in neurons that are continuously depolarizing as in status epilepticus. Finally, Doppler studies of brain blood flow in preeclamptic women suggest that magnesium sulfate vasodilates the smaller-diameter intracranial vessels distal to the middle cerebral artery and may exert its main effect in the prophylaxis and treatment of eclampsia by reversing vasospastic cerebral ischemia.

·         D-Dimer or fibrin split products are useful when abruptio placentae is suspected. These are the most sensitive tests to confirm coagulopathy; however, they are qualitative studies and give little information about the severity of abruption. Recent literature has demonstrated a correlation between elevated CA-125 levels and abruption. This assay has little clinical utility, as it usually requires a long turnaround time. A Kleihauer-Betke test may be useful in the Rh-negative patient. The results are useful in calculating the appropriate dose of Rh immune globulin.

·         The use of erythropoietin was found to increase production of hemoglobin F in baboons; however, it stimulated hemoglobin S production in humans. Hemoglobin F synthesis by stimulating Y-chain production appears to be a promising form of therapy for the sickle cell disease and thalassemia syndrome. Y-chains of hemoglobin F inhibit polymerization of hemoglobin S and therefore inhibit sickling. Recombinant erythropoietin and hydroxyurea have been used together recently with elevation of hemoglobin F. More recently intravenous arginine butyrate has been used with the increase in fetal globin synthesis, production of F reticulocytes, and the level of Y-globin.

·         In recent years the diagnosis of persistent hyperemesis gravidarum has been linked to Helicobacter pylori infection.

·         Previously, it was thought that a hormonal imbalance was related to the clinical manifestations of PMS/PMDD, but the most recent consensus is that physiologic ovarian function is the trigger. This is supported by the efficacy of ovarian cyclicity suppression, either medically or surgically, in eliminating premenstrual complaints.

Further research has shown that serotonin (5-HT), a neurotransmitter, is important in the pathogenesis of PMS/PMDD. Both estrogen and progesterone have been shown to influence the activity of serotonin centrally. Many of the symptoms of other mood disorders resembling the features of PMS/PMDD have been associated with serotonergic dysfunction.

·         Recent evidence indicates that spermicides containing nonoxynol-9 (N-9) are not effective in preventing cervical gonorrhea, chlamydia or HIV infection. In addition, frequent use of spermicides containing N-9 has been associated with genital lesions which may be associated with an increased risk of HIV transmission.

·         Three additional hormonal contraceptives methods have recently become available: The transdermal patch (Ortho Evra, Ortho-McNeil Pharmaceuticals, Inc.), the vaginal ring, (NuvaRing, Organon, Inc.) and a single rod implant system (Implanon, Organon, Inc.).

·         Recently, surgically implantable device like Interstim have been found very useful in patients with intractable urgency incontinence and voiding dysfunction.

·         Many surgeons encourage their patients to sip tap water (not ice water) on the first day after uncomplicated gynecologic surgery. On the following day, clear fluids are often given if bowel sounds are normal, and solid food usually is withheld until the patient passes flatus. Some recent studies suggest that early oral intake (clear liquids on postoperative day 1), even among patients with major abdominal surgery, reduces length of hospitalization and is not associated with an increased incidence of ileus.

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·         Recently, new factors have been discovered that are involved with the regulation of bone remodeling: osteoprotegerin, a naturally-occurring protein with potent osteoclastogenesis inhibitory activity; and RANKL (receptor activator of nuclear factor kappa beta ligand), a transmembrane ligand expressed on osteoblasts.