I'm not a great fan of systematic reviews because so many are done badly, but this is worth it for the Forest plot. It's got all the features you need, including the weighting (how much each study contributes to the final result), stats for heterogeneity (remember than P < 0.05 means the numbers are unlikely to be homogenous), and a stat for whether two subgroups are alike (with and without nicotine replacement therapy).
Everyone knows that if you marry your cousin your children are more likely to have a congenital anomaly. This paper gives some absolute numbers. The baseline risk of an anomaly is about 3%; consanguineous marriage doubles that.*
A couple of other interesting points. The risk of congenital anomaly in this population is much higher for Pakistani than for Bangladeshi people, perhaps because cousin marriage within kinships has been going on for generations in Pakistani groups (known as biraderi). Also if the mother had degree level education, that halved the risk.
*it's interesting to put that the other way round. You can marry your cousin, with all the benefits that brings, and there is still a 94% chance that all will be ok with your baby.
The maths is complex but the concept is simple and it's a really important question. Will the new coronavirus from the Middle East spread globally or not? If each case infects, on average, more than one other person then yes - it will. If each case, on average, infects less than one more person then no - the epidemic will die out.
So we need to collect information on all cases reported so far and try to calculate that crucial number - the basic reproduction number R0
Here is the attempt. Like I say, don't get bogged down in the maths, but note the basic methods.
Note also that the infections must be coming from somewhere, or more precisely from some other livign organism into the human population. But we don't yet know where it is lurking. As the authors point out, it's important to find that out, and quickly.