There is insufficient data for clear guidelines in pregnancies before 34 weeks gestation.
In two randomized, controlled trials in women with severe preeclampsia between 28-34 weeks or 28-32 weeks gestation, aggressive or expectant management was compared and found that duration of gestation had been increased by 7.1 and 15 days, respectively.
A prospective observational trial published in the American Journal of Obstetrics and Gynecology in 2004 studied maternal and fetal outcomes with expectant management between 24 to 33 weeks.
The primary target of this study was the number of days of gestation by which the pregnancy was prolonged after admission.
Other maternal outcomes included death, eclampsia, DIC, HELLP syndrome, pulmonary edema, placental abruption, and acute renal failure.
Fetal outcomes included death, respiratory distress syndrome, necrotizing enterocolitis, NICU admissions, and days spent in NICU.
Nicardipine and labetalol were used intravenously to maintain maternal blood pressure less than 150/110 mm Hg.
Ultrasound, fetal heart rate monitoring, and twice daily evaluation of fetal movements were used to assess fetal well-being.
The study found that expectant management increased gestation by an average of six days for women less than 29 weeks gestation, and four days for both the 29 to 32 week group, as well as the 32 to 33 week group.
During the study, there were no maternal deaths, and 12 out of 13 perinatal deaths occurred in infants delivered before 29 weeks gestation.
The study found no significant differences in maternal outcomes based on weeks gestation.
Furthermore, expectant management incurred minimal risks for the mother, but pregnancy prolongation provides benefits for the fetus/neonate.