Coital rate and pregnancy-induced hypertension.

Previous workers have emphasized the possibility that pregnancy-induced hypertension (PIH) is associated with a change of sexual partner. It is noted here that any such association is far weaker than that between PIH and fecundability (the probability of conceiving in a month at risk). This latter association is so strong as to suggest its closeness to a true cause. Of the determinants of fecundability, coital rate seems the most promising to pursue as a possible cause of PIH.