University of Agriculture (SLU), Uppsala, Sweden.
School of Health and Education, University of Skövde, Skövde, Sweden.
BMC Pregnancy Childbirth. 2019 Aug 9;19(1):285. doi: 10.1186/s12884-019-2365-9.
Oxytocin is a key hormone in childbirth, and synthetic oxytocin is widely administered to induce or speed labour. Due to lack of synthetized knowledge, we conducted a systematic review of maternal plasma levels of oxytocin during physiological childbirth, and in response to infusions of synthetic oxytocin, if reported in the included studies.
An a priori protocol was designed and a systematic search was conducted in PubMed, CINAHL, and PsycINFO in October 2015. Search hits were screened on title and abstract after duplicates were removed (n = 4039), 69 articles were examined in full-text and 20 papers met inclusion criteria. As the articles differed in design and methodology used for analysis of oxytocin levels, a narrative synthesis was created and the material was categorised according to effects.
Basal levels of oxytocin increased 3-4-fold during pregnancy. Pulses of oxytocin occurred with increasing frequency, duration, and amplitude, from late pregnancy through labour, reaching a maximum of 3 pulses/10 min towards the end of labour. There was a maximal 3- to 4-fold rise in oxytocin at birth. Oxytocin pulses also occurred in the third stage of labour associated with placental expulsion. Oxytocin peaks during labour did not correlate in time with individual uterine contractions, suggesting additional mechanisms in the control of contractions. Oxytocin levels were also raised in the cerebrospinal fluid during labour, indicating that oxytocin is released into the brain, as well as into the circulation. Oxytocin released into the brain induces beneficial adaptive effects during birth and postpartum. Oxytocin levels following infusion of synthetic oxytocin up to 10 mU/min were similar to oxytocin levels in physiological labour. Oxytocin levels doubled in response to doubling of the rate of infusion of synthetic oxytocin.
Plasma oxytocin levels increase gradually during pregnancy, and during the first and second stages of labour, with increasing size and frequency of pulses of oxytocin. A large pulse of oxytocin occurs with birth. Oxytocin in the circulation stimulates uterine contractions and oxytocin released within the brain influences maternal physiology and behaviour during birth. Oxytocin given as an infusion does not cross into the mother's brain because of the blood brain barrier and does not influence brain function in the same way as oxytocin during normal labour does.
催产素是分娩过程中的关键激素，合成催产素被广泛用于引产或加速分娩。由于缺乏相关知识，我们对生理分娩过程中产妇血浆催产素水平以及在纳入研究中报告的合成催产素输注时的催产素水平进行了系统评价。
预先制定方案，于 2015 年 10 月在 PubMed、CINAHL 和 PsycINFO 中进行系统检索。在去除重复项后（n=4039），根据标题和摘要筛选检索结果，然后检查 69 篇全文，20 篇论文符合纳入标准。由于这些文章在分析催产素水平的设计和方法上存在差异，因此我们进行了叙述性综合，并根据效果对材料进行了分类。
妊娠期间，催产素基础水平增加了 3-4 倍。从妊娠晚期到分娩，催产素脉冲的频率、持续时间和幅度增加，分娩结束时达到每分钟 3 次脉冲的最大值。分娩时，催产素增加了 3-4 倍。分娩第三阶段也会出现与胎盘娩出相关的催产素脉冲。分娩时的催产素峰值与个体子宫收缩在时间上没有相关性，这表明收缩的控制存在其他机制。分娩期间脑脊液中的催产素水平也升高，这表明催产素被释放到大脑以及循环中。释放到大脑中的催产素在分娩和产后期间诱导有益的适应性效应。输注 10mU/min 以下的合成催产素后，催产素水平与生理分娩时的催产素水平相似。当合成催产素输注率增加一倍时，催产素水平增加一倍。
妊娠期间，血浆催产素水平逐渐升高，在第一和第二产程中，催产素脉冲的幅度和频率逐渐增大。分娩时会出现一个大的催产素脉冲。循环中的催产素刺激子宫收缩，而在大脑中释放的催产素会影响分娩期间母亲的生理和行为。由于血脑屏障的存在，输注的催产素不会进入母亲的大脑，也不会像正常分娩时那样影响大脑功能。
