A review of the effects of Valsalva manoeuvre in labour and birth

In pregnant people with medical conditions that may be exacerbated by Valsalva manoeuvre, caesarean birth may be offered due to concerns about vaginal delivery. Caesarean carries with it its own potential for maternal morbidity, and thus it is important that women are appropriately counselled about the mode of delivery most suited to their individual situation.

The Valsalva manoeuvre is the act of forced expiration against a closed glottis, the physiological effects of which are an increase in intrathoracic and intraabdominal pressure. This has subsequent effects on venous return, heart rate, arterial pressure, cerebral perfusion and intracranial pressure. The Valsalva manoeuvre is a normal physiological act, and similar effects of raised intraabdominal pressure occur with vomiting, coughing and sneezing, for example.

The second stage of labour is defined as the period from full cervical dilatation until delivery of the baby. During the expulsive pushing phase of the second stage of labour, women may spontaneously employ the Valsalva manoeuvre. Additionally, the Valsalva manoeuvre is a key component of traditional coached pushing to assist a woman to effectively push and may also be used in an attempt to minimise the length of the second stage. This involves the woman pushing against a closed glottis, usually coached by a birth attendant and in a supine position. An alternative method is spontaneous pushing where the woman does not push for the duration of the contraction and is guided by the pressure from the fetal head. Directed pushing, using an open glottis technique, is also possible. The open glottis results in less haemodynamic changes and placental blood flow is maintained. This is part of the practice recommended by the World Health Organisation which recommends women be supported to follow their own urge to push.

Throughout this article, the term “woman” is used; however the authors acknowledge that not all pregnant people identify as women. It is important that care provided is sensitive to the needs of those whose gender does not align with the sex assigned at birth.

We outline a review of available evidence on the potential effects of Valsalva manoeuvre on the following systems: central nervous system, vestibular, visual, cardiorespiratory, respiratory and gastrointestinal.

Central nervous system

Increased blood flow is seen in various organs in pregnancy as a result of the approximately 50% increase in blood volume from the first trimester. The brain demonstrates autoregulation to maintain constant cerebral blood flow (CBF). Labour and delivery cause further significant changes in the maternal circulation, with uterine contractions increasing cardiac output by up to 10%. Some studies have looked at the changes in cerebral blood flow in labour. One study ¹ which looked at the effect of labour and pushing on cerebral blood flow demonstrated a fall in middle cerebral artery blood flow during uterine contractions and in the active second stage of labour, associated with an increase in heart rate but no change in systolic, diastolic or mean arterial pressure. The changes in cerebral blood flow were explained by downstream vasodilation.

This change in cerebral autoregulation has potential clinical implications for women with intracranial pathology. Chiari I malformation is a caudal displacement of the cerebellar tonsils below the level of the foramen magnum. Syringomyelia is present in up to 65% of affected women. Symptoms include headaches, neck pain, paraesthesia, gait and balance disturbance. The theoretical risks of Chiari malformation in labour relate to concerns around increased intracranial pressure. While epidural and spinal anaesthesia carry a risk of cerebrospinal fluid leak and herniation, general anaesthesia in labouring women carries a risk of failed intubation, aspiration and subsequent hypoxia. In a systematic review of 34 women with Chiari malformation delivering 35 babies, 20% had a diagnosis made in the pregnancy. ² One of the women underwent a craniectomy during pregnancy, 12 of the women underwent elective caesarean birth to limit changes in intracranial pressure during spontaneous labour, and 4 women had an operative vaginal delivery to limit Valsalva in the second stage of labour. In this review, there were no cases of brainstem compromise secondary to maternal Valsalva in the second stage of labour. The authors concluded that there was no evidence to support one mode of delivery over another but that minimising Valsalva in a woman who is symptomatic is prudent. Operative vaginal delivery under regional anaesthesia was suggested as a reasonable option. In women with significant symptoms, decompression should be considered prior to pregnancy. In labour, epidural boluses of local anaesthesia agents should be delivered cautiously to limit the acute rise in intracranial pressure associated with epidural volume expansion.

One case series ³ of cerebral arterio-venous malformation (AVM) in 979 women of childbearing age found 12 instances of AVM rupture in 492 pregnancies with a rupture rate of 2.75% per pregnancy against an annual rupture rate of 4.14% in women who were never pregnant. There was no rupture associated with vaginal delivery. There is no consensus in the literature about the most appropriate mode of delivery in women with cerebral AVM, with elective caesarean birth and instrumental delivery to limit Valsalva both considered reasonable in current clinical practice.

Vestibular system

Pressure of stress exerted on the ear can result in rupture of the tympanic membrane. In humans the tympanic membrane can withstand only limited pressure and rupture can occur when pressure exceeds 35 kPa. Average intraabdominal pressure in pushing is approximately 25 kPa. ⁴ The most common cause of barotrauma is air travel. Valsalva in labour can increase internal ear pressure. Only two cases of tympanic membrane rupture in labour have been reported in the literature^5,6 although this is likely to be underreported. The management is conservative with no long-term effects on hearing recorded.

Visual system

Ocular complications during labour are rare. The most common is a subconjunctival or preretinal haemorrhage. Preretinal haemorrhage can occur due to the sudden increase in intraabdominal and intrathoracic pressure with Valsalva manoeuvre. This is usually unilateral and is also seen with constipation and straining, weight lifting, coitus, sneezing and coughing. In pregnancy it can occur with the forceful vomiting of hyperemesis and in labour.

Valsalva maculopathy can be associated with a sudden increase in intrathoracic or intraabdominal pressure, such as with Valsalva manoeuvre in labour, which causes an increase in intraocular pressure. This increase in intraocular pressure may rupture superficial retinal capillaries. This is rarely reported in pregnancy and labour.^7,8

Eye disease is a common reason why clinicians may advise a caesarean birth, up to 2% in one study, with the most common condition being myopia. ⁹ There is a concern among some clinicians that forceful pushing could cause a retinal detachment in women with a previous history or with a significant risk factor, and therefore in some centres such women may be offered elective caesarean births. ¹⁰ Rhegmatogenic retinal detachment is caused by a small hole or tear in the retina which is not influenced by changes in eye pressure. ¹¹ Vaginal delivery, therefore, is not a risk factor for rhegmatogenic retinal detachment.^12,13 There is one case report of a haemorrhage in a previously undiagnosed retinal cavernous haemangioma. ¹⁴ This was managed conservatively with full resolution.

Cardiovascular system

Valsalva manoeuvre is clinically useful for assessment of autonomic function status, as a marker for heart failure, for termination of arrhythmias (notably supraventricular tachycardia), murmur differentiation during cardiac auscultation and various other indications. ¹⁵

When a person performs a Valsalva manoeuvre the changes in intrathoracic pressure can dramatically affect venous return, cardiac output, arterial pressure and heart rate. The effect of the VM on arterial aortic pressure occurs in four phases. Initially, with the increase in intrathoracic pressure, an increase in aortic pressure is seen (phase I); however, as the venous return and subsequent cardiac output reduces, so too does the aortic pressure (phase II). During phase I, heart rate decreases because aortic pressure is elevated due to the baroreceptor reflex and similarly in phase II, heart rate increases as the aortic pressure falls. When the person starts to breathe normally again, aortic pressure briefly decreases as the external compression on the aorta is removed, and heart rate briefly increases reflexively (phase III). This is followed by an increase in aortic pressure (and mainly baroreceptor mediated reflex decrease in heart rate) as the cardiac output suddenly increases in response to a rapid increase in cardiac filling (phase IV). Aortic pressure also rises above normal due to the sympathetic nervous system mediated increase in systemic vascular resistance occurring during the Valsalva manoeuvre . Briefly, the increase in intrathoracic pressure during Valsalva manoeuvre reduces venous return, reducing pre-load and subsequently reducing cardiac output.

Clinicians may have theoretical concerns when performing Valsalva manoeuvre for women with pre-existing coronary artery disease, valvular disease or congenital heart disease. ¹⁶

Fortunately, there have been no studies showing any significant adverse effects of VM on coronary artery disease and one study (albeit with a small sample size) demonstrated its safety. ¹⁷

Women with heart failure show an abnormal blood pressure overshoot in response to Valsalva manoeuvre due to impaired ventricular function but it has been used as a diagnostic tool and has again not been demonstrated to have any significant adverse effects. ¹⁸

Valsalva manoeuvre may be used to differentiate between different cardiac murmurs. ¹⁹ Since the manoeuvre reduces preload and thus end-diastolic volume, it can help accentuate the intensity of some murmurs while diminishing others. In phase II, as the venous return and subsequent cardiac output reduces, the effect of Valsalva manoeuvre diminishes the murmurs of aortic and pulmonary stenosis, tricuspid and mitral regurgitation, aortic and pulmonary regurgitation and mitral and tricuspid stenosis. In hypertrophic obstructive cardiomyopathy (HOCM), a Valsalva manoeuvre will increase the intensity of the murmur due to the decrease in preload to the right side of the heart, resulting in decreased left ventricular end-diastolic volume. In women with mitral valve prolapse (MVP), a Valsalva manoeuvre will decrease left ventricular volume causing the click and murmur to occur earlier in systole and become more prominent changing both the character and intensity of the murmur. In summary, murmurs that decrease in intensity with the Valsalva manoeuvre are related to valve lesions such as mitral regurgitation and aortic stenosis, and murmurs that increase in intensity with the Valsalva manoeuvre include MVP and HOCM.

In congenital heart disease, specifically women with a patent foramen ovale (PFO), VM increases the intrathoracic pressure of the chest and reduces pulmonary venous return, which results in decreased left ventricular filling. The pressure of the left ventricle and atrium is subsequently lower than that of the right side, which can result in right-to-left shunting through the PFO. There has been one case report of amniotic fluid embolism in women with underlying PFO. ²⁰ The shunting of blood flow across the PFO was attributed to raised intra-thoracic pressure in labour.

Respiratory system

Pneumothorax, either primary spontaneous or secondary occurring with underlying lung pathology, is a rare event in pregnancy. Following a systematic review of 87 cases from the literature, the authors concluded that vaginal delivery was not contraindicated but that elective instrumental delivery to limit propulsive efforts in the second stage of labour was advisable. ²¹

Gastrointestinal system

In pregnant women with portal hypertension and varices, there are no guidelines on management; however consensus opinion is that caesarean birth should be for the usual obstetric indications. ²² Repeated Valsalva manoeuvre increases the risk of variceal bleeding. It has been suggested forceps or vacuum delivery could be considered to shorten the second stage in these women. ²³ For women with high grade oesophageal varices, decisions about mode of delivery should be multidisciplinary lead with involvement of the woman and her family. ²⁴

Discussion

The Valsalva manoeuvre has many diagnostic indications and is used as part of the cardiovascular examination, assessment of urinary incontinence and female pelvic organ prolapse, in addition to its common use to equalise pressure between the ear and sinuses with changes of atmospheric pressure in air travel and scuba diving. Abnormal responses to the Valsalva manoeuvre are seen in people with a number of different underlying conditions. Potential harmful effects of the more prolonged Valsalva that is seen in coached pushing in labour include an increase in intraabdominal pressure which may impair placental blood flow as evidenced by more CTG abnormalities, ²⁵ increased maternal fatigue ²⁶ and perineal trauma in labour. ²⁷

In women with an underlying medical disorder which, in theory, may be exacerbated by changes in intraabdominal, intrathoracic or intracranial pressure, a caesarean birth may be recommended as an alternative although there is often little evidence to support that decision. The National Institution for Health and Care Excellence (NICE) outline some conditions where caesarean birth may be recommended such as in women considered at high risk of intracerebral haemorrhage or in certain cardiac conditions such as pulmonary arterial hypertension or those with a NYHA class III or IV. ²⁸ In many cases however there is no “one size fits all” approach and any discussion must take into account the woman's wishes, obstetric history and severity of the underlying condition. Caesarean birth carries its own risks including an increased risk of post-partum haemorrhage, venous thromboembolism, wound complications and implications for future pregnancies including placenta accreta spectrum. A balance of risks must be met between what is often a theoretical risk of physiological changes in labour and delivery and the potential for severe maternal morbidity with caesarean delivery. A reasonable alternative to avoid the active pushing phase of the second stage of labour is with epidural to allow for passive descent of the head followed by elective instrumental delivery. NICE recommend up to 2 h passive descent for nulliparous women or 1 h in multiparous women with an epidural followed by directed pushing. ²⁹

A number of conditions have been implicated in Valsalva manoeuvre in labour. These range from extremely rare events to theoretical concerns based on our understanding of the physiological changes of pregnancy and Valsalva; however, there are very few instances in which vaginal delivery is absolutely contraindicated. It is important that women are appropriately counselled about their delivery options to reach the decision that best suits them. Counselling should include a discussion about alternatives to Valsalva manoeuvre including pushing using an open glottis breathing technique. The alternative method is spontaneous pushing where the woman does not push for the duration of the contraction and is guided by the pressure from the fetal head, or physiological pushing. The glottis is open resulting in less haemodynamic changes and placental blood flow is maintained. This practice is recommended by the World Health Organisation, ³⁰ as an alternative to the active management of labour encompassing coached pushing, as coached pushing is viewed as prescriptive and may increase the likelihood of intervention. It must be noted however that the availability of trained birth attendants varies greatly between countries, particularly in low resource settings.

Potential benefits of coached pushing include a shortened second stage, although this in itself is of uncertain clinical significance. ³¹ A randomised controlled trial comparing delayed pushing in lateral position with Valsalva manoeuvre found that second stage times were the same but the women had reduced fatigue and pain scores on self-reported scales with delayed pushing. ³² It is recognised that passive descent in the second stage in nulliparous women is associated with an increase in spontaneous vaginal delivery and lower instrumental delivery rates. ³³ Physiological pushing may be associated with greater maternal satisfaction. ³⁴

In our unit, we hold weekly multidisciplinary team meetings including obstetricians (both general and those with a special interest in maternal medicine), obstetric anaesthesiologists, midwives and physicians from relevant specialties. The women are counselled and are involved in their delivery plans at their antenatal appointments, and a plan is documented and given to the woman for their own records. It is our experience that some women enter pregnancy believing they will have to have a caesarean because of an underlying medical condition even though this may not be the case.

Conclusion

From a review of the available maternal medicine literature, there are very few absolute contraindications to vaginal delivery. Very rarely adverse events can occur with sustained VM in the second stage of labour, even in women without prior risk factors. For women in whom prolonged Valsalva manoeuvre may have adverse effects, regional labour analgesia and elective instrumental delivery is often a safe alternative. The correct mode of delivery is the one in which the women and her team are most comfortable minimises potential risks. In women with complex medical needs, caesarean birth may be recommended by her team but this decision should be individualised, taking into account the woman's preference and obstetric history. Caesarean birth should not necessarily be the default option. Multidisciplinary team discussion with obstetrics, midwifery, anaesthesia and physicians can tease out the best option for particular cases. Women should be counselled on the risks and alternatives, including alternatives to traditional coached pushing employing a Valsalva manoeuvre technique, so that they may make an informed decision on the mode of delivery best-suited to them.