Oligohydramnios at Term: A Case Report

Maria L. Lanni, CNM, MS; Elizabeth A. Loveless, CNM, MS

Disclosures

J Midwifery Womens Health. 2007;52(1):73-76. 

In This Article

Management of Oligohydramnios

Oligohydramnios at term may be managed actively via induction of labor or expectantly via hydration and fetal surveillance, and/or regular ultrasounds assessing amniotic fluid volume.[2,4] While both options exist, active management is the common approach for women with term pregnancies with or without maternal or fetal obstetric risk factors.[4,12,14]

Inducing labor in women with low-risk pregnancies with isolated oligohydramnios is the most common practice, although it is not found to improve perinatal outcome.[4,12,14] In a small prospective, randomized pilot study (N = 54), Ek et al.[14] found that active versus expectant management of oligohydramnios in women with uncomplicated pregnancies at term resulted in no difference in maternal or neonatal outcomes. Because of the small number of women in the study group, this study did not have sufficient power to determine a significant relationship between oligohydramnios and neonatal outcomes. Conversely, a prospective study by Alchalabi et al.[4] divided 180 women between 37 and 42 weeks' gestation who were admitted for induction of labor into 2 groups: the women in one group had an AFI ≤5 cm (n = 66) and the women in the other group had an AFI of >5 cm. Although the 2 groups had comparable demographic and obstetric characteristics prior to induction, the women in the low AFI group had an increased rate of cesarean section secondary to fetal distress (27.3% vs 5.5%; OR 6.75, 95% CI 1.8-23.2; P = .004).[3] Conway et al.[13] randomized 61 otherwise healthy women with isolated oligohydramnios (AFI ≤5 cm) at term to expectant management or induction and found no differences in maternal or neonatal outcomes. These authors concluded that expectant management with twice weekly fetal surveillance is a sensible alternative to labor induction, and that the majority (67%) of women will go into labor spontaneously within 3 days after diagnosis.[13] Although small and insufficiently powered, these studies suggest that isolated oligohydramnios does not appear to be associated with adverse outcomes, but it may cause fetal intolerance of labor, which does result in higher cesarean rates. Expectant management may have equally good neonatal outcomes, yet that approach is not widely used.[14]

One approach to treating oligohydramnios during labor is to perform an amniotomy followed by amnioinfusion to increase the fluid inside the uterus.[5] However, if expectant management is desired, maternal hydration can increase the AFI. Oral or IV maternal hydration has been studied as a treatment for oligohydramnios in women with otherwise healthy term pregnancies.[5] In the second trimester of pregnancy, the majority of the amniotic fluid is produced through fetal urine production and is reabsorbed through fetal swallowing. Amniotic fluid is also reabsorbed via the fetal lungs and by the placenta.[15,16] Maternal hydration and maternal osmolarity affect the amount of amniotic fluid available to the fetus for urine production and reabsorption near term.[15,17] In a systematic review, Hofmeyr[5] found that amniotic fluid volume is increased in women who have reduced or normal AFI and who drank 2 liters of water or who received IV hypotonic hydration; isotonic IV hydration had no measurable effect.[5] The amniotic fluid volume, assessed 6 hours later, was shown to increase by an average effect size of 2.01 (95% CI, 1.43-2.60) with oral hydration, and 2.3 (95% CI, 1.36-3.24) with a hypotonic IV solution. While no clinically important outcomes were assessed in any of these trials, hydration is a simple, inexpensive, and noninvasive method that may apply to clinical situations. Leeman and Almond[3] reported an increase of 30% in the AFI in women who consumed 2 liters of water 2 to 5 hours before repeat ultrasound, compared to women who were not orally hydrated. They recommend that maternal hydration should be considered before retesting the AFI 2 to 6 hours later, in cases of isolated oligohydramnios (Figure 1).

Proposed algorithm for managing oligohydramnios. EFW = Estimated fetal weight; FGR = fetal growth restriction. Reprinted with permission from Dowden Health Media.[3]

In the case presented here, the woman had isolated oligohydramnios at 41 weeks' gestation with no other risk indications or risk factors for maternal-fetal adverse outcomes. The result of her induction of labor was a cesarean section for arrest of descent because of maternal exhaustion, not for non-reassuring fetal status. The duration of time from admittance to delivery was 37 hours. No intervention or observational testing occurred during the first 12 hours of hospital admission.

In Conway's[13] retrospective, case-controlled study, women who were induced for oligohydramnios had an increased rate of cesarean section when compared women with oligohydramnios who were in spontaneous labor. The authors postulated that this increase was caused by the induction process itself.[13] One may conclude that a woman who is at term with isolated oligohydramnios with reassuring fetal surveillance and the absence of maternal morbidity and evidence of FGR is not associated with adverse perinatal outcome.

Many questions remain regarding how we measure and assess fetal intolerance of labor. How valid are the cut off measures that we use for oligohydramnios? Is the increase in cesarean section secondary to fetal intolerance of labor from low AFI or the induction process itself? More clinical research needs to be done to evaluate neonatal outcomes following expectant management of women with oligohydramnios.

In the case presented here, alternative approaches to diagnosing oligohydramnios could have led to a different outcome. One approach is to advise adequate oral hydration before doing a routine BPP to avoid potentially unnecessary and risky interventions. However, the clinical outcomes of the fetus and mother following acute maternal hydration have not been researched and warrant further studies. Challenges of inter- and intrarater reliability of AFI determination suggests that all medical, midwifery, and nursing staff may benefit from periodic review of technique of measurement.

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