What are the recommended management and treatment options for a pregnant woman at 33 weeks gestation?

From the Guidelines

At 33 weeks gestation, the management of a pregnant woman should prioritize fetal growth restriction (FGR) assessment and preparation for potential preterm delivery, with a focus on minimizing morbidity, mortality, and optimizing quality of life. According to the Society for Maternal-Fetal Medicine consult series #52 1, the definition of FGR is an ultrasonographic estimated fetal weight or abdominal circumference below the 10th percentile for gestational age.

Key Recommendations

• Delivery at 33-34 weeks of gestation is recommended for pregnancies with FGR and absent end-diastolic velocity (AEDV), as stated in the guidelines 1.
• Serial umbilical artery Doppler assessment should be performed to assess for deterioration, with weekly evaluations for decreased end-diastolic velocity or severe FGR 1.
• Antenatal corticosteroids should be administered if delivery is anticipated before 33 6/7 weeks of gestation, to reduce respiratory morbidity and improve neonatal outcomes 1.
• Maternal nutrition and prenatal care should continue, with monitoring of maternal blood pressure, weight, urine protein, and fetal heart rate, as well as ultrasound assessment of fetal growth, position, and amniotic fluid volume.

Fetal Monitoring and Delivery Timing

• The decision for delivery in FGR is driven by fetal and maternal factors, including estimated fetal weight, gestational age, and findings on fetal surveillance 1.
• Delivery at 37 weeks of gestation is recommended for pregnancies with FGR and an umbilical artery Doppler waveform with decreased diastolic flow but without AEDV/REDV or with severe FGR 1.
• In the presence of reversed end-diastolic velocity (REDV), delivery at 30-32 weeks of gestation is recommended, due to the high risk of neonatal morbidity and mortality 1.

Additional Considerations

• Women at risk of preeclampsia should continue low-dose aspirin (81 mg daily) if already prescribed, and consider high-dose calcium supplementation (≥1 g/day) to reduce the risk of pre-eclampsia and pre-term birth 1.
• Screening for gestational diabetes should be completed, and women should be educated about monitoring fetal movement and recognizing signs of preterm labor.

From the FDA Drug Label

Teratogenic Effects. Pregnancy Category C Teratogenic studies were conducted in mice and rats at dosages of 0. 5,1,2, and 4 mg/kg/day. Except for retarded fetal ossification at 4 mg/kg/day considered secondary to the decreased average fetal weights, no increase in fetal malformations was observed as compared with control groups Other studies in mice reported in the literature using higher doses (5 to 15 mg/kg/day) have described maternal toxicity and death, increased fetal resorptions, and fetal malformations. However, animal reproduction studies are not always predictive of human response There are no adequate and well controlled studies in pregnant women. Indomethacin should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus Nonteratogenic Effects Because of the known effects of non-steroidal anti-inflammatory drugs on the fetal cardiovascular system (closure of ductus arteriosus), use during pregnancy (particularly late pregnancy) should be avoided The known effects of indomethacin and other drugs of this class on the human fetus during the third trimester of pregnancy include:

• constriction of the ductus arteriosus prenatally,
• tricuspid incompetence, and pulmonary hypertension;
• nonclosure of the ductus arteriosus postnatally which may be resistant to medical management;
• myocardial degenerative changes,
• platelet dysfunction with resultant bleeding,
• intracranial bleeding,
• renal dysfunction or failure,
• renal injury/dysgenesis which may result in prolonged or permanent renal failure,
• oligohydramnios,
• gastrointestinal bleeding or perforation, and increased risk of necrotizing enterocolitis.

The recommended management and treatment options for a pregnant woman at 33 weeks gestation are not explicitly stated in the provided drug label. However, considering the potential risks associated with indomethacin use during pregnancy, caution is advised. The drug label recommends avoiding the use of indomethacin during pregnancy, particularly in the late stages, unless the potential benefit justifies the potential risk to the fetus 2. Close monitoring of the fetus and the mother is necessary if indomethacin is used during pregnancy. It is essential to weigh the potential benefits against the potential risks and consider alternative treatment options.

From the Research

Management and Treatment Options for Preterm Labor at 33 Weeks Gestation

• The management and treatment options for a pregnant woman at 33 weeks gestation with preterm labor include the use of tocolytic agents such as nifedipine, magnesium sulfate, and indomethacin 3, 4, 5, 6.
• Nifedipine has been shown to be effective in prolonging pregnancy and reducing the risk of respiratory distress syndrome, necrotizing enterocolitis, intraventricular hemorrhage, neonatal jaundice, and admission to the neonatal intensive care unit compared to β₂-adrenergic-receptor agonists and magnesium sulfate 3.
• A comparison of nifedipine and indomethacin used in preterm labor tocolytic treatment found that both treatments had significant effects on fetal-maternal Doppler blood flows and perinatal outcomes, but further studies are needed to support these results 4.
• A systematic review and meta-analysis comparing the efficacy of transdermal nitroglycerin and oral nifedipine in managing preterm labor found that both treatments demonstrated similar efficacy in prolonging pregnancy and influencing neonatal outcomes, but with different side effect profiles 5.
• Another systematic review and meta-analysis comparing the effectiveness and safety of nifedipine and magnesium sulfate in the treatment of preterm birth found that nifedipine was more effective with a faster onset of action and a longer prolonging pregnancy, and may be safer with fewer maternal side effects and better neonatal outcomes 6.
• The effects of nifedipine on fetal cardiac function in preterm labor have been evaluated, and studies have found that nifedipine treatment does not appear to have any significant effect on fetal cardiac function or morphology 7.

Tocolytic Agents and Their Effects

• Nifedipine: effective in prolonging pregnancy, reducing the risk of respiratory distress syndrome, and has a faster onset of action and a longer prolonging pregnancy compared to magnesium sulfate 3, 6.
• Magnesium sulfate: associated with a higher incidence of maternal side effects, such as tachycardia, flushing, palpitations, dizziness, and nausea, and a higher incidence of neonatal respiratory distress syndrome compared to nifedipine 6.
• Indomethacin: has significant effects on fetal-maternal Doppler blood flows and perinatal outcomes, but further studies are needed to support these results 4.
• Transdermal nitroglycerin: demonstrates similar efficacy to nifedipine in prolonging pregnancy and influencing neonatal outcomes, but with a different side effect profile 5.