Introduction
Almost every maternal system adapts to pregnancy, under the influence of progesterone, oestrogens, hCG and the growing uterus. Knowing the normal changes stops them being mistaken for disease.
Main changes
Normal weight gain is about 11–16 kg for a woman of normal BMI (less if she is obese).
Hygiene and diet in pregnancy
- Folic acid 400 µg daily from before conception to 12 weeks (5 mg if there is a high risk of neural tube defects, e.g. previous affected child, epilepsy treatment, diabetes, obesity).
- Iodine 150 µg daily; vitamin D supplement; iron when anaemic.
- Extra energy only about 300 kcal/day in the 2nd and 3rd trimesters; a varied diet rich in protein, calcium and fibre.
- Avoid alcohol completely, smoking, raw meat and unpasteurised dairy (toxoplasma, listeria), liver and vitamin A excess, fish high in mercury.
- Regular moderate exercise is safe; avoid contact sports and diving.
- Travel: flying is generally safe up to 36 weeks; prevent thrombosis on long journeys.
- Sexual intercourse is allowed unless there is bleeding, placenta praevia or risk of preterm birth.
- Vaccines: influenza and pertussis (Tdap) are recommended in pregnancy; live vaccines (rubella, varicella) are not given.
Cardiac output, plasma volume and GFR all rise by about half: that one fact explains the murmur, the dilutional anaemia and the low creatinine of pregnancy.