Starting a family: Pregnancy - the first trimester, weeks 1-12

It all begins with a tiny embryo, weighing 1g. The heart first begins to “flutter” but from about seven weeks a heartbeat will be detectable on ultrasound.

The bodily changes – and the symptoms – you start to experience are fuelled by hormones – oestrogen, progesterone, human chorionic gonadotrophin (hCG) and human placental lactogen (hPL).

A missed period may alert you to the fact that you are pregnant. However, some of those first symptoms: tiredness, bloating, sore breasts, mood swings, even bleeding, may mean that you initially confuse pregnancy with PMS.

Other early include symptoms include headaches, an increased urge to urinate, constipation, heartburn and indigestion, light-headedness and, of course, nausea.

“There is no such thing as ‘morning sickness’,” says Martina Dillon, lead midwife with Cork University Maternity Hospital’s Domino service. “Many women will say they have been vomiting morning, noon and night. It can seem endless, but it can also be reassuring that all is well with the pregnancy. Try eating dry toast or plain biscuits before getting up in the morning. Eat small amounts often.”

Not every mother-to-be experiences all, or any, of the common symptoms of early pregnancy. “Many women sail through the first 12 weeks with no symptoms other than tiredness,” says Dillon. “Get the feet up as soon as work is over, but fresh air and walking can actually help. Eat lots of iron-rich foods and fruit.”

Dillon’s advice for when you learn you are pregnant: “Stop smoking and using alcohol and drugs. Eat a healthy diet, begin a folic acid supplement if you are not already on one, and take regular exercise. Get informed on maternity care options and make an appointment with a GP. Research complementary therapies which may be helpful for pregnancy and labour, for example, hypnobirthing, acupuncture, reflexology and yoga. However, stay away from the internet and don’t over-Google!”

During this trimester your metabolism, heart rate, circulation and breathing rate will all increase, and a plug of mucus is formed in your cervix to protect the growing baby. You will not look pregnant – though your breasts may increase in size.

By the end of this trimester your baby will be excreting urine, will have distinguishable facial features, and even the beginnings of nails on its fingers and toes.