The NHS commissioning group covering the Horsham and Mid Sussex area has one of the lowest rates of smoking mothers in England, according to the latest figures.
There were 525 pregnancies in the second quarter of 2017 - and 19 mothers who smoked throughout their pregnancy, or 3.7 per cent.
This is up from 3.4 per cent in the same period last year.
The NHS wants to reduce the number of mothers who smoke while pregnant to 6 per cent - a new target which was revised down from 11 per cent earlier this year.
This means Horsham and Mid Sussex was one of just 33 Clinical Commissioning Groups in England which met this new target, from a total of 2007.
Smoking during pregancy has been steadily decreasing in recent years, down from 5 per cent four years ago.
Pregnant smokers have been one of the key targets of the Department of Health’s tobacco strategy, because of the risk of serious health complications for both mother and child.
When a woman smokes during pregnancy, it restricts the flow of oxygen to the unborn child, which can lead to complications during labour, increased risk of miscarriage and stillbirth.
The figures show 11 per cent of mothers in England smoked at the time of delivery - up slightly from 10.8 per cent in the previous quarter of 2017, and significantly higher than the NHS target. The England figure has been decreasing year on year since records began, down from 15 per cent in 2006.
There is also wide regional variation in the figures: the NHS region with the highest number of smoking mothers was Cumbria and the North East, with 15.8 per cent of all pregnancies - more than three times the rate in London, where just 5.1 per cent of mothers smoked.
Blackpool’s Clinical Commissioning Group has highest rate of smoking mothers in the country, where more than one in four women smoked throughout their pregnancy, according to the latest figures.
Smoking is more common among pregnant women from disadvantaged groups, according to the Department of Health. Children who grow up with a smoking parent are also more likely to become smokers themselves.