Although I'm a research biologist, I work closely with an NHS clinic in the company of a lively band of doctors and nurses. I suspect they're as fascinated by my mucking about with test tubes, stains and microscopes as I am by their patient exams and diagnoses. But it wasn't until I belatedly stumbled over a fascinating paper from a Canadian scholar, published earlier this year, that another key difference became clear.

There isn't a huge gender imbalance amongst physicians – in the UK about 40% are women, and projections suggest they will be the majority in a few years. Other countries show a similar pattern.

This situation contrasts sharply with academic biology, where for decades roughly equal numbers of women and men have embarked upon that career path, only to end up with a small minority of female professors – a trend reflected globally. It's such a problem that a Commons Select Committee is currently calling for evidence about the "leaky pipeline" for women in science, technology, engineering and maths.

I've written before about this topic, as have many others. The gender difference between science and medicine, however, is something I've noticed but have never really stopped to wonder about. Perhaps I've been too preoccupied stressing about where my next short-term contract will come from, as my female colleagues drop like flies around me (and my male colleagues quietly get tenure).

The reasons for gender imbalance in the sciences are undoubtedly complex and multifactorial. The Canadian paper, which focuses mostly on the situation in North America but is comparable to the UK, hypothesises and provides compelling evidence that one main reason academic science is less populated with women than is medicine – despite both starting with nearly equal numbers of trainees – is not that it's more stressful, lower-paid, requires longer hours – or is even less "family friendly" overall. Rather, it's that the most competitive time in each career differs sharply. For medicine, the bulk of the competition occurs during the fight to get into medical school – this happens before most people start families. Once in, you're pretty much guaranteed a job at the other end, as intake is sensibly regulated with a view towards supply and demand. On the other hand, in academia, while it's relatively easy to get into graduate school, the steepest competition – getting one's first faculty position – coincides with peak childbearing years. And with the sharp career pyramid structure in academic science, in which cheap disposable trainees perform the vast bulk of scientific research, only a tiny fraction of PhD students will ultimately get jobs in academia (about 4% in the UK), making that competition even fiercer.

It's an interesting hypothesis, and the entire paper, by Professor Shelley Adamo, is available free of charge if you want to know more. Presumably it could very well apply to other careers where pivotal milestones occur during peak childbearing.

But such musings are no longer abstract for me. I am currently eight months' pregnant with my first baby, and have been for several years lodged firmly in a grey zone between an independent research post and a tenured one. Competition, I can report from the front line, is indeed intense – it's pipettors at dawn, with everyone scrambling over the small scraps of grant funding available.

There are, however, other career-negative factors that I never truly considered until I was in this position. And I don't just mean being unable to button up my white coat. The whole experience has been psychologically fraught in a way that I had never envisaged.

Take the first three months, before I felt comfortable telling anyone about the pregnancy. I had to eat constantly to keep the nausea at bay, which didn't always work during an intense experiment when I was unable to leave my test tubes unattended. (Although many health and safety rules in the lab are over-the-top, not eating amidst toxic chemicals and pathogenic bacteria probably isn't one of them.) I don't think my productivity dropped, but it was extremely unpleasant. Then as I started to show – not so easy to hide from my colleagues, the majority of whom are obstetricians or gynaecologists – I agonised about when and how to confess to my two (male) bosses. I use the word "confess" deliberately, because I felt a keen sense of guilt, as if I were betraying their trust, somehow disrespecting their decision to hire me. Rationally I knew that I was only planning on taking four months of maternity leave, and that I have a legal and human right to procreate. But somehow the guilt was overwhelming, so much so that I often lay awake at night feeling physically sick imagining how the conversations might go. I wasn't even sure at that point, with my contract soon to expire, that I was eligible for occupational maternity pay.

Another worry, given my contract's looming demise, was that it would be impossible to seek employment elsewhere once I started to show. Who would hire a newly pregnant woman if they could get someone else who would not drop out again a few months later? And then after giving birth, would I fall behind during maternity leave and the inevitable adjustment period when I went back to work? Would I publish fewer papers, which would mean a less competitive CV for securing those already impossible to get grants? Would my international competitors pip me to the post on key projects?

Thankfully, a lot of my worries to date have turned out to be unfounded. Although I almost had a heart attack broaching the topic, both of my bosses seemed genuinely delighted at my news, and remain extremely supportive of my long-term career. The university turns out to have a wonderful maternity policy that does not discriminate against open-ended or short-term contracts. My current grant will be frozen in my absence, so the relentless clock will stop while I'm up to my elbows in nappies instead of test tubes – meaning I don't have to job-hunt just yet. I've recently had a few promising funding leads for the future. And though I don't think it will be a piece of cake getting back into the swing of things, I benefit from the inspiration of a number of new-mum colleagues who have managed to make it seem, if not easy, then at least doable.

All of this uncertainty is helped tremendously by how much I love science in general, and my research project in particular. The work is important and fulfilling, the experiments have been successful, and every morning I open the lab door dying to know what results the team will come up with that day. I can't imagine ever doing anything else.

So bring on the biggest experiment I've probably ever conducted in my life. I'm ready.

Jenny Rohn is a cell biologist at University College London, looking forward to being a yummy mummy in September. Follow her continuing adventure on twitter at @JennyRohn.