5 weeks pregnant: what is happening this week

The heart starts this week. The NHS still puts the embryo at around 2 mm - a sesame seed rather than a poppy seed, which tells you how little the ruler has moved - and inside that, a tube of tissue folds and begins to beat for the first time. Blood vessels already exist. The umbilical cord and the placenta are being built in parallel, and the nervous system has begun: the brain and spinal cord are taking shape before almost anything else. If there is a single week where the ratio of significance to visible size is at its most absurd, this is a fair candidate. Symptoms tend to arrive around now and they are not subtle. Exhaustion of a kind that sleep does not fix, a metallic taste, sore breasts, nausea that ignores the word morning, a sense of smell that has become a liability. None of these are a measure of anything. Strong symptoms do not indicate a stronger pregnancy and their absence does not indicate a weaker one; the variation between people is enormous and it is not diagnostic. What is worth doing is naming them out loud, because a partner who knows why the kitchen is suddenly unbearable can act on it.