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If you opt to have ultrasound scans during your pregnancy, the sonographer will typically give you an indication of how big (or small) your baby is. Based on the measurements taken (such as the length of the thigh bone and circumference of the abdominal cavity) an estimated weight will be calculated and this will be used to determine whether your baby is big or small when plotted against standard foetal growth charts. At antenatal appointments around 28 weeks of gestation, your fundal height will be measured (length from your pubic bone to the top of your uterus) and your midwife may also palpate your abdomen to again estimate the size of your baby. All of these measurements have a margin of error (of up to a pound) and are extremely subjective! Measurements taken by different sonographers, midwives, etc on the same mother on the same day can all result in different values and can vary just by the way you or your baby are positioned at that discrete moment in time; considering the pressure you may then be under to ‘do’ something about it, this is something to bear in mind!

Indeed, a mother’s own intuition and estimate of her baby’s weight is more indicative of the actual weight of the baby when compared to clinical or ultrasound-based estimates.  For the purposes of the information that follows, ‘big baby’ means a weight over 4kg/8lb13oz/90th percentile at term, while ‘small baby’ means a weight of less than 2.5kg/5lb8oz/10th percentile at term.

Bella ~ Born at home ~ 10lb 4oz

Bella ~ Born at home ~ 10lb 4oz

In regards to having a homebirth when a ‘big baby’ has been deemed to be a possibility, midwives may quote shoulder dystocia (when the baby gets ‘stuck’ because the shoulder/s cannot pass through the pelvis) as a reason why a homebirth should not be attempted. Interestingly, one study estimates that half of all shoulder dystocia cases happen in babies under the 4kg threshold. Techniques such as the Gaskin or the McRoberts manuevers can help in releasing the shoulder to allow the baby to be birthed without further complication. Being at home, in general, however, can actually ease the entry of ‘big babies’ into this world because the mother is free to move, sway, and adapt positions which she instinctively feels will help her birth her baby safely. This is in comparison to being attached to a monitor and restricted to being either very close to or on a bed when in hospital, which means the pelvis is not being moved to help guide the baby into the best position for birth. Also, one must keep in mind that it is not in the body’s best interest to grow a baby which is too large to be birthed vaginally; therefore, it is unlikely that your baby will be too big for you to birth.

Additionally, a ‘big baby’ may be easier to birth than a smaller baby! This may be due to the malposition of a smaller baby (such as having its hands up by its head) or due to the lower amount of pressure being placed on the cervix to dilate from a lesser weight baby.

Adriana ~ Born at home ~ 2.94kg

Adriana ~ Born at home ~ 2.94kg

When a ‘small baby’ has been identified, the immediate concern is that the baby is not growing due to a condition called Intrauterine Growth Restriction (IUGR) although there may be a suspected abnomality causing the baby to be ‘small’. In the case of suspected IUGR, this may be due to a variety of reasons, including a problem with the placenta. However, a ‘small baby’ may also be simply due to the genetic background of the mother and father (due to race or stature of the mother and father) or simply due to the normal margins of error associated with ultrasound. If this is indeed the case and no other factors have been identified as a cause for a ‘small baby’, the concern regarding a homebirth may be due to the fact that the baby may not be able to regulate its temperature well or that the suckling reflex will be weak, leading to feeding issues. Skin-to-skin contact/Kangaroo Mother Care has been shown to be as effective, if not more so, than placing the baby in an incubator to keep it warm, and it can also help with the initiation of breastfeeding. If feeding is an issue, contact your local breastfeeding clinic or lactation consultant for support.

Of course, the choice to have a homebirth is yours to make, but being fully informed of the risks and benefits of homebirth in regards to either of these circumstances can help you and your partner make the appropriate decision for your family.

Further suggested reading:

Big babies:

Midwife Thinking – Shoulder Dystocia The Real Story

Big Babies – The Curse of (mis) Diagnosing a Macrosomic Infant (Part 1)

Big Babies – Birthing a Macrosomic Infant (Part 2)

A home birth story: The Hackney Doula – “Big Babies: I can probably do anything I ever wanted to do in the universe ever”

Small babies:

Midwifery Today – Kangaroo Care

RCOG: Investigation & Managment of the small for gestation fetus

Written by Cathy & Lisa who are doulas.  Lisa also had a baby who had growth scans for suspected IUGR and was born at home just after his due date, weighing 8lb 5oz & Cathy gave birth to her 4.14kg/9lb 2oz baby at home