Baby's Heart Rate Dropping in Labour

What a change in the trace means, and does not mean

A baby's heart rate varies constantly in labour. It speeds up with movement, slows briefly with some contractions, and settles between them. NICE's fetal monitoring guideline sets out how the features of a trace are categorised, and the categories themselves make the point: a trace is called normal, suspicious or pathological, based on whether individual features are scored white, amber or red.

Suspicious is not an emergency, and pathological is not a diagnosis of harm. NICE asks teams to "take into account any change in the categorisation of the CTG alongside other antenatal and intrapartum risk factors", to discuss the change and its implications with you, and to take your preferences into account when deciding how to proceed.

The conservative measures, in order

NICE's first response is not to deliver the baby. It is to look for a reversible cause. "If there are any concerns about the baby's wellbeing", teams should start one or more conservative measures based on an assessment of the most likely cause:

• Position. Maternal position "can affect uterine blood flow and cord compression", so you are encouraged to move, to adopt an alternative position, and to avoid lying on your back.
• Low blood pressure. If you are hypotensive after an epidural top-up, intravenous fluids are started, you are moved to a left lateral position, and an anaesthetist is called to review.
• Too many contractions. Contraction frequency is reduced "by reducing or stopping oxytocin if it is being used", and a tocolytic drug to relax the uterus may be offered.

NICE also asks teams to act if five or more contractions occur in ten minutes: perform a full risk assessment, take action to reduce the frequency, "explain to the woman what is happening, and ensure that she has adequate pain relief".

Two things NICE says not to do

Both are worth knowing, because both were once standard and are still remembered by families.

Oxygen through a mask: "Do not offer maternal facial oxygen therapy as part of conservative measures because it may harm the baby." NICE allows it where it is needed for the mother herself, or as preparation before an anaesthetic — but not as a treatment for the baby's heart rate.

Amnioinfusion, putting fluid into the uterus: "Do not offer amnioinfusion for intrauterine fetal resuscitation."

NICE is also specific about fluids: do not offer intravenous fluids to treat fetal heart rate abnormalities unless you are hypotensive or have signs of sepsis.

Asking the baby a question

If the trace is suspicious and there are risk factors, NICE says teams may "consider digital fetal scalp stimulation" — gently rubbing the baby's scalp during an examination. A healthy baby usually responds with an acceleration in heart rate.

NICE describes both outcomes. If stimulation "leads to an acceleration in fetal heart rate and a sustained improvement in the CTG trace", monitoring continues. If there is no acceleration, that "is a worrying sign that fetal compromise may be present, and that expedited birth may be necessary".

What happened to fetal blood sampling

Taking a small blood sample from the baby's scalp to measure acid levels used to be a standard next step in the UK. It is no longer recommended, and it is not recommended against either.

NICE's position is stated in one sentence: "NICE is unable to make a recommendation about fetal blood sampling because of limited evidence." Practice therefore varies between units, and if it is offered or declined to you, the reason is local policy rather than a national rule. That is a fair thing to ask about.

The features that worry teams most

Variability — the small beat-to-beat fluctuation in the heart rate — carries particular weight. NICE: "If there is an absence of variability, carry out a review of the whole clinical picture with a low threshold for expedited birth, as this is a very concerning feature."

It also cautions against over-reading normal quiet periods: variability is usually between 5 and 25 beats a minute, and "intermittent periods of reduced variability are normal, especially during periods of quiescence ('sleep')". A baby having a sleep cycle on a monitor is a common reason for a temporary change that resolves.

In the second stage NICE asks for extra caution, noting that interpreting traces then "is more challenging than in the first stage", with a lower threshold for a second opinion, and that the baby's heart rate must be distinguished from yours at least every five minutes.

If the measures do not work

Expediting birth means bringing it forward, and how depends entirely on where you are. If the cervix is fully dilated and the baby is low, an assisted vaginal birth with ventouse or forceps may be the fastest safe route; the RCOG publishes patient information on what that involves. If it is not, a caesarean is likely, and its urgency will be categorised.

NICE's intrapartum guideline lists an obstetric emergency, including a need for advanced neonatal resuscitation, among the findings that prompt transfer to obstetric-led care, and asks that a member of the team be allocated to talk with you and your birth companions throughout.

Where you are matters

Away from an obstetric unit, a concerning heart rate is one of the recognised reasons for transfer. NICE reproduces the Birthplace in England figures: an abnormal fetal heart rate accounted for 7.0% of transfers from planned home births, 10.5% from freestanding midwifery units and 10.8% from alongside midwifery units. Delay in labour was a larger reason in every setting.

The HSE describes the monitoring options in Irish units, including a waterproof handheld doppler, which is why intermittent listening remains possible in a pool.

What to ask in the room

What have you seen, and is it suspicious or pathological? What do you think is causing it? What are we trying first? How long will we give it? What would make you recommend birth now?

NICE asks that changes and their implications are discussed with you and your preferences taken into account. Asking for the plan out loud is not obstructive — it is the conversation the guideline expects to happen.