The effect of oxytocin in induced labour on neonatal jaundice

Pulsatile oxytocin for induction of labor: a randomized prospective controlled study

In a prospective randomized study, 20 patients with term pregnancies underwent induction of labor with either continuous or pulsed (every 8 minutes) intravenous oxytocin infusion. There were no significant differences with respect to induction-labor interval, induction-delivery interval, cesarean section rates, need for pain relief and Apgar scores. Sixty percent of patients receiving continuous oxytocin infusion developed uterine hyperstimulation but only 10% receiving pulsed oxytocin did so. However, the difference was not significant. The mean +/- SEM total amount of oxytocin given by continuous infusion was 4237 +/- 1066 mU which was 70% more than by pulsatile infusion (2454 +/- 808 mU). The highest rate of oxytocin infused was significantly lower by pulsatile administration (5.2 +/- 0.8 mU/min) than by continuous infusion (9.2 +/- 1.8 mU/min, p = less than 0.05). Our study demonstrates that pulsed administration of oxytocin every 8 minutes is as effective and safe as continuous intravenous infusion of oxytocin for induction of labor, requires less oxytocin with therefore, a wider margin of safety and is consistent with the pulsatile release of oxytocin during normal labor.

Effect of saline and glucose infusions of oxytocin on neonatal bilirubin levels

OBJECTIVE

To ascertain the effect of isotonic saline and glucose infusions of oxytocin on neonatal bilirubin levels.

METHOD

Eighty-two parturient Nigerian women requiring oxytocin infusion in labor were randomized into two groups receiving 0.9% saline or 5% glucose, respectively. A group of 82 women not requiring oxytocin were recruited for comparison. All had sodium and bilirubin estimations in cord plasma and neonatal bilirubin assay on Day 3.

RESULT

Analysis of variance revealed higher mean cord and neonatal bilirubin levels in the glucose group compared with the other two (P < 0.05). Significant inverse correlation was observed between cord plasma sodium and neonatal bilirubin levels in all groups. Hyperbilirubinemia occurred in 55% of babies in the glucose group compared with 21% and 22% in the saline and control groups, respectively (P < 0.001).

CONCLUSION

The use of isotonic saline rather than 5% glucose solution as vehicle for oxytocin infusion in labor appears to be associated with lower neonatal bilirubin levels.

Induction of labor with pulsatile oxytocin

In a prospective, randomized study, 106 patients underwent induction of labor with either pulsed (every 8 minutes) (n = 50) or continuous (n = 56) intravenous infusion of oxytocin. Maternal characteristics, gestational age at induction, induction-delivery interval, analgesia for labor, cesarean section rates, and newborn characteristics were similar in both groups. The mean +/- SEM total oxytocin administered was significantly less in the pulsed group (3564 +/- 487 mU) than in the continuous group (7684 +/- 844 mU; p less than 0.0001); the average dose of oxytocin administered per minute was significantly lower in the pulsed group (3.9 +/- 0.3 mU/min) than in the continuous group (7.8 +/- 0.4 mU/min; p less than 0.0001); the peak or highest administered dose of oxytocin expressed per minute was also signficantly lower in the pulsed group (9.6 +/- 0.8 mU/min) than in the continuous group (14.1 +/- 0.7 mU/min; p less than 0.0001). These significant differences persisted even when controlled for parity, Bishop's score of the cervix, and number of days induction of labor was carried out. Uterine hyperstimulation occurred infrequently in both groups (3.6% to 4.0%). The pulsed group required a significantly smaller infusion volume (25 +/- 14 ml) than the continuous group (780 +/- 84 ml; p less than 0.0001). Thus pulsatile administration uses significantly less oxytocin and infusion fluid but is as effective and safe as continuous infusion.

The endocrinology of parturition in the human

Current evidence suggests that oestrogens, progesterone, relaxin, the prostaglandins, and oxytocin are all hormones concerned to a major degree with the onset and maintenance of parturition. Oestrogens, relaxin, and the prostaglandins are particularly involved with cervical ripening, while prostaglandins, progesterone and oxytocin are more involved in regulating myometrial contractility. Catecholamines may also have some regulatory function in relation to uterine contractions. Progesterone dominance during pregnancy is associated with a firm closed cervix, few myometrial gap junctions, low calcium levels in the cells, and a quiescent myometrium. At term, a change in the oestrogen/progesterone balance favours cervical ripening and increased uterine activity. Of particular importance at the level of the muscle cell are changes in the number of oxytocin receptors; a complex interaction between cAMP and phosphoinositide metabolism governs the intracellular level of calcium, thus regulating contractile activity.

Oxytocin induction of labour: hyponatraemia and neonatal jaundice

To determine the effects of fluid restriction in induced labour with oxytocin in 5% dextrose solution, maternal venous blood and fetal cord venous blood were examined in 164 mothers in induced labour and 29 mothers with a spontaneous onset of labour. After satisfactory uterine activity was induced either the oxytocin infusion was managed according to routine delivery unit practice (n = 36), or infusion rates were halved (n = 45), or quartered (n = 43), or discontinued (n = 40). Despite fluid restriction during labour the mean sodium concentration in maternal blood or cord blood had fallen to a similar extent in all four induced groups at delivery. Potassium, urea, creatinine, total protein, and albumin in maternal blood or cord blood were affected differently by induced labour as compared with sodium. The fall in sodium concentration in maternal blood was a more consistent reflection of the total volume of fluid received, mean infusion rates and cord blood sodium after infusion rates were quartered or discontinued. The incidence of hyponatraemia was 5% in mothers and 8% in infants. A comparison of hyponatraemic and normonatraemic cord blood showed no significant differences in serum bilirubin levels or red cell counts, but more hyponatraemic infants developed neonatal jaundice. It is suggested that in induced labour fluid restriction alone does not prevent hyponatraemia and neonatal jaundice.

A multicentre prospective randomized controlled trial of induction of labour with an automatic closed-loop feedback controlled oxytocin infusion system

A randomized prospective controlled trial of an automatic feed-back controlled oxytocin infusion system (AIS) for the induction of labour at term was carried out in three hospitals. In primiparae, a four-fold reduction in the total dose of oxytocin infused, for the same induction-delivery interval, was achieved with the AIS compared with standard labour ward protocols relying on midwife control of oxytocin infusion rate. In multiparae, the total dose of oxytocin infused was almost halved when the AIS was used, while the mean duration of labour was increased by 1.6 h to 7.5 h. There were no differences in the mode of delivery or Apgar scores. It is concluded that the AIS is a safe technique for induction of labour. Its use has demonstrated that term labour can be induced efficiently with a mean oxytocin infusion rate between 2.5 and 3 mU/min (max 8.8 mU/min) and a total oxytocin dose infused of less than 5 U.

Vacuum extraction and neonatal jaundice

Various fetal scalp lesions are related to the use of the vacuum extractor. Blood sequestered in these lesions could result in an increased bilirubin load on the functionally limited neonatal liver, leading to the development of hyperbilirubinemia. In the present study bilirubin levels of vacuum extracted neonates were compared with those of non-instrumentally delivered babies during the first 72 hours of life. Sixty-nine vacuum extracted neonates had higher bilirubin levels than 56 non-instrumentally delivered babies at 24 (114 mumol/l vs. 96 mumol/l), 48 (163 vs. 141) and 72 (194 vs. 144) hours of age. The p values were 0.05, less than 0.025 and less than 0.001 respectively. This trend was apparent in both oxytocin induced and non-induced deliveries and whether or not phototherapy cases were included in the analysis. The incidence of hyperbilirubinemia requiring phototherapy was higher after vacuum extraction than after non instrumental delivery (27.5% vs. 12.5%; p less than 0.04). Analysis of our results unexpectedly indicated that oxytocin induction was generally associated with an attenuation of bilirubin levels after both vacuum extraction and spontaneous delivery. The clinician attending newborn babies should be aware of the higher incidence of neonatal hyperbilirubinemia associated with vacuum extraction.