15.7 — Labour and Birth

Maternal mortality in Britain in 1900 was around 1 in 200 births. Today it is around 1 in 10,000 — a fiftyfold reduction, achieved through antisepsis, blood transfusion, antibiotics, safe caesarean section and skilled attendance.

Worldwide it remains around 1 in 5,000 overall, and around 1 in 40 in the worst-affected countries. The difference is almost entirely access to skilled care, not biology.

And the great majority of maternal deaths are from a small number of causes, all of which are treatable: haemorrhage, infection, hypertensive disease, obstructed labour and unsafe abortion.

What starts labour

Not fully understood, which is worth admitting given how central it is.

Several factors contribute.

A shift in the oestrogen-to-progesterone balance — progesterone keeps the uterus quiet, and its restraining effect declines.

Increased oxytocin receptors on the myometrium — the uterus becomes far more sensitive to oxytocin without oxytocin levels necessarily rising much.

Prostaglandins — which soften the cervix and stimulate contractions.

Fetal signals — the fetal adrenal and hypothalamus appear to contribute, which fits the observation that the fetus has some influence over its own delivery timing.

Uterine stretch.

And the cervix must change before labour can progress. Cervical ripening — softening, thinning and moving forward — happens over days to weeks beforehand, and it is why induction begins with ripening agents rather than with oxytocin.

The three stages

First stage — cervical dilation

From the onset of regular contractions to full dilation at 10 centimetres.

Latent phase — irregular contractions, cervix effacing and dilating to about 4 to 6 centimetres. Can last many hours to days, and it is where most women are at home.

Active phase — regular strong contractions every 2 to 3 minutes, dilation progressing more predictably.

Duration: first baby, typically 8 to 18 hours in the active phase; subsequent babies considerably shorter.

And the traditional expectation of 1 centimetre per hour has been substantially revised. Zhang's work on modern labour curves showed that normal labour is slower than the older Friedman curve suggested, particularly before 6 centimetres, and that applying the old standard led to unnecessary intervention. Definitions of delay have been relaxed accordingly.

Contractions — the myometrium contracts and does not fully relax, so the upper uterus progressively shortens and thickens while the lower segment thins. This is retraction, and it is what draws the cervix up over the presenting part rather than simply squeezing.

Second stage — delivery of the baby

From full dilation to birth.

Typically up to 2 to 3 hours in a first labour with an epidural, and often under an hour without.

And the fetus performs a specific sequence of movements, which is the mechanical consequence of the pelvic geometry in Chapter 5.6.

Engagement — the widest part of the head enters the pelvic inlet, which is widest side to side, so the head enters facing sideways.

Descent.

Flexion — the chin tucks onto the chest, presenting the smallest diameter of the head.

Internal rotation — as the head reaches the pelvic floor it rotates 90 degrees to face backward, because the outlet is widest front to back.

Extension — the head extends under the pubic bone and is born.

External rotation (restitution) — the head turns back to line up with the shoulders.

Expulsion — the anterior shoulder delivers under the pubic bone, then the posterior, then the body.

No other primate's infant performs this rotation (Chapter 3.6), and it is the direct cost of combining a large head with a pelvis adapted for walking.

Perineal tears are graded:

First degree — skin only. Second degree — into the perineal muscle. Third degree — involving the anal sphincter. Fourth degree — through into the rectal lining.

Third and fourth degree tears — obstetric anal sphincter injuries — occur in around 3 percent of vaginal births and are the ones that matter, because inadequate repair causes faecal incontinence.

Which is why they are repaired by someone trained to do it, in theatre, with follow-up — and why recognising them requires a deliberate examination rather than an assumption.

Warm compresses and hands-on perineal support during delivery reduce them measurably.

Episiotomy — a deliberate cut. Routine episiotomy has been abandoned, because trials showed it produced worse outcomes than allowing a natural tear. It is used selectively, for instrumental delivery and for fetal distress requiring rapid delivery.

Third stage — delivery of the placenta

Usually 5 to 30 minutes.

And this is the most dangerous stage of a normal birth, because the placental bed is a raw surface with the entire uterine blood flow — around 500 to 800 ml per minute at term — passing through it.

Bleeding stops through the mechanism in Chapter 15.3: the myometrium contracts and its interlacing fibres clamp the vessels.

Active management — a uterotonic drug given as the anterior shoulder delivers, controlled cord traction, and uterine massage. It reduces postpartum haemorrhage by around 60 percent and is standard practice.

Pain relief

Labour pain is genuinely severe — consistently rated among the most intense pains measured — and it varies enormously between women, which is worth stating because both minimising and catastrophising it are unhelpful.

Non-pharmacological: continuous support from a companion, mobility, water immersion, breathing techniques, TENS, and massage.

And continuous one-to-one support has some of the best evidence of anything on this list — it reduces the use of pain relief, shortens labour and reduces caesarean rates, in a substantial Cochrane review. A person who stays with you is an evidence-based intervention.

Nitrous oxide with oxygen — inhaled during contractions. Takes effect in about 30 seconds and wears off quickly, so it is self-titrated. Modest analgesia, and it makes some women nauseated.

Opioids — pethidine or diamorphine. Moderate effect, and they cross the placenta and can depress the newborn's breathing if given close to delivery.

Epidural — local anaesthetic and opioid into the epidural space (Chapter 5.3).

The most effective form of labour analgesia by a wide margin, and its effects are worth stating accurately.

It does not increase the caesarean rate, which was believed for years and has been examined in multiple trials.

It does modestly prolong the second stage and increase the rate of instrumental delivery.

It causes low blood pressure in some women, which is why fluid is given and blood pressure monitored.

Post-dural-puncture headache occurs in around 1 percent, if the needle passes too far (Chapter 11.10).

And serious complications are rare — permanent nerve damage in the order of 1 in 100,000.

Spinal anaesthetic — a single injection into the cerebrospinal fluid. Faster and denser than an epidural, and it is what is usually used for caesarean section.

Caesarean section

Around 20 to 35 percent of births in most high-income countries, and over 50 percent in some.

And the rate is genuinely contested. The World Health Organization's position is that rates above around 10 to 15 percent do not improve maternal or neonatal mortality at population level, while acknowledging that individual indications must be met.

Both extremes cause harm. Too few caesareans means obstructed labour, fistula and death (Chapter 5.6). Too many means surgical complications, and a cumulative risk in future pregnancies of placenta praevia and accreta (Chapter 15.6).

Categories by urgency:

Category 1 — immediate threat to life. Target 30 minutes from decision to delivery.Category 2 — maternal or fetal compromise, not immediately life-threatening. Target 75 minutes. Category 3 — needs early delivery, no compromise. Category 4 — elective.

Common indications: previous caesarean, failure to progress, fetal distress, breech presentation, placenta praevia, and multiple pregnancy.

Risks compared with vaginal birth: higher rates of infection, bleeding, blood clots and injury to bladder or bowel; longer recovery; and the cumulative risks in future pregnancies.

Benefits: avoiding the risks of the specific complication it is performed for, and lower rates of pelvic floor injury and incontinence.

Vaginal birth after caesarean (VBAC) succeeds in around 70 to 75 percent of attempts. The main risk is uterine rupture at the scar, at around 0.5 percent, which is why it requires continuous monitoring and immediate access to theatre.

The emergencies

These are the reasons obstetrics is staffed the way it is, and each has a defined response.

Postpartum haemorrhage — over 500 ml after vaginal birth or 1,000 ml after caesarean. The leading cause of maternal death worldwide.

The causes are remembered as the four Ts, and the order reflects their frequency.

Tone — uterine atony, and it accounts for around 70 percent. The uterus fails to contract, so the vessels are not clamped. Treated with massage, uterotonic drugs, and if necessary balloon tamponade, compression sutures or embolisation.

Trauma — tears, or uterine rupture.

Tissue — retained placenta or fragments.

Thrombin — a clotting abnormality.

And tranexamic acid reduces death from bleeding when given within 3 hours, established by the WOMAN trial — the same drug and the same time-dependence as in trauma (Chapter 13.7).

Shoulder dystocia — the head delivers and the anterior shoulder is caught behind the pubic bone.

It is an emergency because the cord is compressed and the baby cannot breathe. There are 4 to 6 minutes.

And there is a defined sequence of manoeuvres, of which the first two resolve the majority: McRoberts' position — the mother's legs sharply flexed onto her abdomen, which rotates the pelvis and flattens the sacrum — and suprapubic pressure. Then internal rotational manoeuvres.

What must not be done is pulling harder on the head, which causes brachial plexus injury (Chapter 11.8) without helping.

Cord prolapse — the cord slipping below the presenting part after the membranes rupture, and being compressed.

Immediate delivery is required, usually by caesarean. In the meantime, the presenting part is lifted off the cord manually, the mother is placed knee-to-chest or head-down, and the bladder may be filled to lift the head.

Uterine rupture — sudden severe pain, abnormal fetal heart rate, and loss of the presenting part from the pelvis. Immediate surgery.

Amniotic fluid embolism — rare, sudden, and often catastrophic: collapse, respiratory failure and disseminated intravascular coagulation. Largely unpredictable and unpreventable.

Eclampsia — seizures. Magnesium sulfate, control of blood pressure, and delivery (Chapter 15.6).

Fetal monitoring

Intermittent auscultation — listening periodically. Appropriate for low-risk labour, and it produces outcomes as good as continuous monitoring in that group.

Continuous cardiotocography — recording the fetal heart rate and contractions.

And its history is a cautionary tale worth telling. Continuous monitoring was introduced universally in the 1970s on the assumption that detecting distress earlier would prevent cerebral palsy.

It did not. Trials showed it reduces neonatal seizures modestly and does not reduce cerebral palsy or death, while substantially increasing caesarean and instrumental delivery rates.

The reason is that the test has poor specificity: an abnormal trace is common and usually does not indicate a compromised baby. Most cerebral palsy originates before labour begins, which no amount of monitoring during labour can address.

It remains appropriate for high-risk labour and inappropriate as a universal intervention, and it is one of the clearest examples in medicine of a plausible technology being adopted before it was tested.

After delivery

The first hour — skin-to-skin contact, which stabilises the newborn's temperature, blood sugar and heart rate, and supports breastfeeding initiation.

Delayed cord clamping — 1 to 3 minutes, transferring an extra 80 to 100 ml of blood and improving iron stores (Chapter 7.9).

Vitamin K — to prevent haemorrhagic disease of the newborn (Chapter 7.1).

Apgar score at 1 and 5 minutes — appearance, pulse, grimace, activity, respiration, each scored 0 to 2.

And its purpose is frequently misunderstood. It describes the baby's condition and guides resuscitation; it is not a prediction of long-term outcome, and a low 1-minute score with a normal 5-minute score is common and reassuring.

Newborn examination within 72 hours — checking heart, hips, eyes and testes.

Newborn screening — the heel-prick blood spot at day 5 (Chapter 4.6).

Newborn hearing screening — otoacoustic emissions (Chapter 11.12).

The postnatal period

Uterine involution — the uterus returns to pelvic size within about 2 weeks and to near its original size by 6.

Lochia — vaginal discharge, red for a few days, then brown, then pale, over 4 to 6 weeks.

Perineal healing, and pelvic floor exercises should begin early.

And the postnatal period is where care has been weakest.

Around half of maternal deaths occur after delivery, and the postnatal check has historically been brief and focused on the baby.

What should be asked about:

Mood. Baby blues affect 50 to 80 percent — tearfulness and mood swings around days 3 to 5, resolving within two weeks. Postnatal depression affects 10 to 15 percent, is often missed, and is highly treatable. Postpartum psychosis affects 1 to 2 per 1,000, usually begins within two weeks, and is a psychiatric emergency with risk to mother and baby.

Bleeding, pain, and infection.

Continence and prolapse — asked about specifically, because women rarely volunteer it (Chapter 5.6).

Sexual function — resumption is guided by comfort, and difficulty is common and usually temporary.

Contraception. Ovulation can return before the first period, and as early as 3 to 4 weeks in a woman who is not breastfeeding, which is why contraception is discussed before discharge rather than at six weeks.

And venous thromboembolism — the risk is highest in the six weeks after delivery, and it remains a leading direct cause of maternal death. Mobilisation, hydration and prophylactic anticoagulation where indicated.

What the next page fixes

Chapter 15.8 covers what happens next — how milk production works, what is actually in breast milk, the honest evidence on breastfeeding, and the newborn's first weeks.