Category Archives: Pregnancy

Giving birth after a caesarian delivery

We are due our second child in February next year (a 20-month gap between no.1 and no.2 – yes, I’m weary just thinking about it). I shall spare you the warts-and-all birth story, but our first baby was born by caesarian section after a worrying dip in his heart rate.

There are two options for women in this situation. The first is to choose to have a caesarian delivery again, which is known as “elective repeat caesarian delivery”, or ERCD for short. The second is to have a “vaginal birth after caesarian”, often abbreviated to VBAC. The actual process of attempting a VBAC is called “trial of labour after caesarian”, or TOLAC.

If we were living forty years ago, there wouldn’t be much debate – we would have been booked in for a C-section. This started to change in the 1980s as more women and couples pushed to have a more ‘natural’* vaginal birth, which led to an increasing number of VBACs. This was backed by improving caesarian surgery, such as a change from making the incision ‘up’ the belly (‘longitudinal’) to making it ‘across’ the belly (‘transverse’) to achieve more effective repair, as well as advice from leading health organisations to reduce caesarian rates.

It seems that in the UK, however, as in many other countries, caesarian deliveries after previous caesarians are back on the increase. One reason is the real fear that the uterus, weakened by the surgery, even by a transverse section, might rupture if a vaginal birth is attempted. A ruptured uterus can lead to complications for the mother and child (more on the specifics in a minute).

There are currently no randomised trials to compare the risks associated with two approaches and most studies have looked retrospectively at what happens in ERCDs or VBACs. This means that it’s hard to inform women before they give birth what the different risks might be.

An article in the scientific journal PLOS Medicine earlier this year – ‘To VBAC or Not to VBAC‘ by Catherine Spong – summarised two research papers that were published at the same time. They both capture information on what the mother intended to do, as well as what actually happened. This gives some relevant insight into whether preferences were successfully carried out, and what the true risks are for women planning either an ERCD or VBAC.

And good news, there’s no paywall so access is free!

The headline message for the woman is:

…risks such as uterine rupture are higher for women attempting a trial of labor following a previous cesarean delivery than those having an elective repeat cesarean delivery; however, the overall risks are low in both groups.

So how does it break down?

The mother

One study was based in the UK and the other in Australia, and both calculated that the uterus ruptures in approximately 2 in 1,000 planned VBAC cases and 1 in 1,000 planned ERCD cases. These figures are lower than those previously reported and communicated to patients, which range from 4-12 ruptures in every 1,000 women planning VBACs. The authors of the Australian study put this down to the hospitals following standardised treatment plans that were designed using the latest evidence. Either way, the results are encouraging.

The British study also found that the risk of rupture is higher for women who have had two or more previous caesarean deliveries, less than 12 months since their last caesarean section, or whose labour was induced (up to roughly 6 in every 1,000 cases, if I’ve calculated correctly, so still relatively low).

As for how the intended modes of delivery played out, nearly 98% of women who planned an ERCD succeeded, but only 57% of those who planned a VBAC did. Almost 25% of women originally planning a VBAC ended up choosing a caesarian delivery, which suggests they either changed their minds or doctors advised that a caesarian should be carried out instead.

The baby

The Australian study also assessed the outcomes for the babies. The researchers recorded fewer serious problems for the babies in the ERCD group when compared with the babies in the VBAC group – approximately 1 in a 100 ERCD births had difficulties, whereas over 2 in a 100 VBAC births had problems for the baby. Serious problems that needed treatment included physical birth injuries, infection and low oxygen in the umbilical cord.

There were two stillbirths in the VBAC group, but as Catherine Spong explains in the summary piece, there’s an important caveat to note. Elective caesarians, by their nature of being chosen, happen at a set time – in the Australian study the C-sections were performed, on average, after 38.8 weeks of term. Laboured vaginal births, by their nature of being involuntary, cannot be booked in, and the average time that these took place was at 40 weeks of term. As a result, it is uncertain whether these stillbirths were associated with the type of delivery or the extra time in the womb (or, even, that they happened by chance – 2 is a very low number from which to draw conclusions).

The state of play

Uterine rupture can increase the risk of stillbirth. According to statistics cited in Spong’s article from the National Institutes of Health in the US, infant death occurs in 6% of cases of a ruptured uterus – given the rates of rupture reported by these two studies, it puts the estimated risk somewhere in the region of 3 deaths every 50,000 ERCDs and 6 deaths every 50,000 VBACs.

Uterine rupture can also increase the risk of brain damage to the baby due to a lack of oxygen (‘hypoxic-ischaemic encephalopathy’, or HIE). Another review estimated this risk to be one in every 1,250 VBACs against practically zero risk in ERCDs.

However, these ever-so-slightly higher risks of complications in VBACs need to balanced against other potential problems associated with caesarian deliveries. Serious infant respiratory problems are more common in elective caesarians (observed to be 3-6 in 400) compared with vaginal deliveries (observed to be 1 in 400). Newborns are also more likely to be admitted to the neonatal intensive care unit (NICU) due to the need for ventilation therapy and more likely to spend longer than seven days in hospital. Other caesarian-specific risks to the mother, such as dislodged blood clots, need for a blood transfusion, extended wound healing, a longer stay in hospital and future pregnancy complications, are also present.

The extent of some of these risks is greatest in the cases of caesarian sections following failed VBACs, which means understanding which women are most likely to have a successful VBAC is hugely important. A group of US clinicians highlighted various factors that increase the likelihood of a successful VBAC: women with one previous caesarian delivery with a low transverse incision, women who at some point have had a prior successful vaginal delivery, and women who had their caesarian because the baby presented breech or some other form of malpresentation rather than for other reasons. Vaginal births in general are more successful when women have access to high level of healthcare, something we should always seek to protect and improve wherever necessary.

Other factors decrease the likelihood of a successful VBAC: failure of the labour to progress or baby to descend during a previous TOLAC, a higher age and weight of the mother, and preexisting medical conditions such as hypertension or diabetes.

And, so…?

What does all this population data mean for the individual woman? The risks for TOLAC seem reasonable in the context of the inherently uncertain process of labour, but women should be properly prepared and counselled to understand the benefits and risks. This should ideally be done with full reference to real numbers and so that the discussion takes the individual’s status into account. That way, the chances of a satisfactory outcome for mother, child and doctor can be at its greatest.

___________________________________________________

*I hesitate to use natural to describe vaginal births: ‘natural’ has so many connotations about medical interventions and vaginal births vary from case to case, which renders ‘natural’ a bit of a messy description.

Do all babies start off female?

There was a bit of coverage last week in the scientific and popular press about some research that appears to refute the idea that the human Y chromosome could disappear at some point in our evolutionary future. In early mammals, the Y chromosome was the same size as the X chromosome but, during the course of our evolution has shrunk to a fraction of the size. This has led to the theory that the Y chromosome could disappear altogether if this shrinking carries on, but the new study has challenged this notion by showing that Y has, in fact, remained a fairly stable size over the last 25 million years. It seems that we may be arriving, or have arrived, at the bare essentials – the non-critical genes have been stripped away over time and natural selection has preserved the vital ones.

The jury’s still out on whether the Y chromosome will become extinct – “we won’t nail it without a crystal ball”, said Professor Darren Griffin of University of Kent in a Guardian article – but this sparked a memory of a conversation I had a while ago about what it is to be ‘male’ or ‘female’.

Some of wife’s friends had been debating whether or not all babies “start off as females”. This debate arose, I guessed while desperately trying to recall my high school biology classes, because of the fact that all fertilised embryos develop along the same path, regardless of the genetic make-up of the embryo. This is until certain genes on the Y chromosome (if present) are activated at around eight weeks and male-associated hormones, chiefly testosterone, are produced that act on some cells to start forming male-specific organs. Without these hormones kicking in, which is the case  in XX embryos when no Y chromosome in present, the cells in the developing embryo go on to form female-specific organs. This means that fertilised embryos under normal circumstances will develop female-specific sex organs unless a hormone cue is activated that signals otherwise.

So all embryos are female, then?

Hmm, perhaps not. One can still make a genetic distinction between males and females at the very point of fertilisation – XX chromosomes will give rise to females and XY will lead to males – and this remains static throughout an individual’s development (and, indeed, life). There are, however, some clinical oddities that throws some confusion into the mix. Some males, for instance, have two X chromosomes but develop as males instead of females because of the presence of a third, Y chromosome that contains the genes to provide the male hormone cues (“Klinefelter’s syndrome“).

So could we define maleness as the presence of at least one Y chromosome (some males are XYY too)?

Not really, because that definition comes unstuck when we consider individuals who are XX but develop as males (at least outwardly), due to the gene for the male hormone cue being copied to one of the X chromosomes (“XX male syndrome“), or individuals who are XY but develop as females, due to a defective Y chromosome (“Turner syndrome“) or mutated Y genes (“Swyer syndrome“).

This leads to complications when trying to enforce a purely genetic definition of gender. The International Olympics Committee for years attempted to enforce this view to adjudicate on cases of gender uncertainty, believing that this represented a more definitive and less intrusive test than physical examination. In this Y-centric definition, without ever meeting an individual and having only a few of their cells, the presence of the Y chromosome or any of its genes (such as the male sex determining gene called ‘Sex-determining Region Y’ (SRY)) would lead to the conclusion that those cells came from a man.

However, for the reasons I mentioned above about all the genetic uncertainties, pressure from a number of medical associations in the USA thankfully led to this sort of test being dropped by 2000. A ‘one-or-the-other’ test of this sort simply does not fully account for the complexities of gender and can lead to discrimination and unfair impediment. The lead opponent of such gender screening, Georg Facius, even proposed a ‘third gender’ for those that could be considered both male and female. One instance where this could be applicable is in cases of “Androgen insensitivity syndrome“, in which XY individuals show abnormal responses to the masculinising hormone androgen. Because the effects can vary, some individuals are anatomically male but have reduced fertility (mild), some possess ambiguous genitalia (partial), while some are almost indistinguishable from XX females (complete).

Even going back to the possible demise of the Y chromosome casts doubt on this Y-centric world. The experts that do anticipate the disappearance of Y are not predicting the end of ‘males’, rather they envisage another sex determining mechanism will take over. This happened before the emergence of the Y chromosome (sex was determined by environmental factors, such as temperature, and still is in some reptiles) and occurs in mammals where the Y chromosome has disappeared (in spiny rats, for example, the male-specific genes have hitched onto other chromosomes).

And this is all before we get into the complex world of gender identity, such as when an individual of one gender is uncomfortable being associated with that gender, which may be environment-driven (or may not be, or may be a little bit). Nor have I touched on psychological and behavioural differences, which lie on a continuous and overlapping spectrum between males and females and are often socially defined (and therefore subject to variation and change).

So none of this means that an embryo is female before the male signals kick in. It is perhaps more accurate to say that an embryo is gender-neutral, i.e. neither male nor female, until towards the end of the embryonic period, at which point anatomical differences start to become apparent in the foetus. But even then, as highlighted above, someone may share characteristics of both sexes and remain ‘double gender’.

Which is all a long-winded of way of saying that a binary male-female distinction is a little fuzzy.