High-Risk Pregnancies and Multiple Gestations

High-Risk Pregnancies

• Causes: Maternal and/or fetal conditions, including intrauterine growth restriction (IUGR), excessive fetal growth, congenital anomalies, birth asphyxia, trauma, prematurity (birth before 24 hours), infection (chorioamnionitis).
• Infections: Group B streptococcus and Escherichia coli are common neonatal sepsis pathogens; Listeria monocytogenes is less common. Vaginal flora bacteria (anaerobic), Mycoplasma hominis, Ureaplasma urealyticum, and Chlamydia trachomatis can also cause amniotic fluid infections. Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is a risk for infants with skin infections or known exposure.
• Risk Factors: Increased risk of fetal infection with a longer latent period (time between rupture of membranes and labor), especially >24 hours. Intrapartum antibiotics reduce risk of neonatal sepsis.

Multiple Gestations

• Risks: Polyhydramnios, preterm birth, IUGR, abnormal presentation (breech), congenital anomalies (intestinal atresia, porencephaly, and single umbilical artery), intrauterine fetal demise, birth asphyxia, and twin-to-twin transfusion syndrome.
• Twin-to-Twin Transfusion Syndrome (TTTS): High mortality, occurring only in monozygotic (identical) twins sharing a placenta with an arteriovenous connection.
  • Donor Twin: Anemia, growth restriction, oligohydramnios.
  • Recipient Twin: Larger, plethoric, polycythemic, polyhydramnios.
• Diagnosis: Weight differences (20%) and hemoglobin differences (5 g/dL) suggest TTTS. Ultrasound reveals discordant amniotic fluid volume.
• Treatment: Attempting to ablate the arteriovenous connection (using a laser).
• Birth Order: Second-born twins have an increased risk of breech position, birth asphyxia, birth trauma, and respiratory distress syndrome.

Toxemia of Pregnancy

• Definition: Preeclampsia/eclampsia, a vascular disorder of unknown etiology.
• Manifestations: Maternal hypertension, uteroplacental insufficiency, IUGR, intrauterine asphyxia, maternal seizures, maternal death.
• Risk Factors: Nulliparity (first pregnancy), twin gestation, chronic hypertension, obesity, renal disease, positive family history of toxemia, diabetes mellitus.
• HELLP Syndrome: A severe subcategory of preeclampsia with hemolysis, elevated liver enzymes, and low platelets. May be associated with fetal inborn error of fatty acid oxidation.

Fetus and Newborn

• Perinatal Mortality: Fetal deaths from the 20th week of gestation to 28 days after birth. Intrauterine fetal death accounts for 40-50%
• Stillbirth: Born without a heartbeat, apneic, limp, pale, cyanotic. Often show maceration, pale peeling skin, corneal opacification, and soft cranial contents.
• Neonatal Mortality: Deaths from birth to 28 days of life. Modern neonatal intensive care allows many newborns with severe conditions to survive, but some die of their original diseases or complications of treatment.
• Postneonatal Mortality: Deaths from 29 days to one year.
• Infant Mortality Rate: Includes neonatal and postneonatal mortality. The US rate was 5.5 per 1000 live births in 2019; the rate was approximately 10.9 per 1000 for Black infants.
• Causes of Perinatal/Neonatal Death: Congenital anomalies, diseases of premature infants are significant causes.
• Low Birthweight (LBW): Infants with birth weight less than 2,500 g.
  • Cause (Developing countries): IUGR
  • Cause (Developed countries): Prematurity
• Very Low Birth Weight (VLBW): Infants with birth weight less than 1,500 g. VLBW infants have a much higher risk of neonatal death than LBW infants, 200-fold.
• Maternal Risk Factors for LBW: Previous LBW birth, low socioeconomic status, low maternal education, poor antenatal care, young/advanced maternal age, short interval between pregnancies, cigarette smoking, alcohol/drug use, physical/psychological stress, single parent, low prepregnancy weight.